Max fuel economy?

[More Power]

If you were building an engine for maximum fuel economy, which would you choose?

1- A non-turbo 6.2L.
2- A TD 6.2L.
3- A non-turbo 6.5L.
4- A TD 6.5L.

I'll add more later, but I wanted you guys to think about fuel economy and what it takes to get it. :D

MP

[john8662]

This is purely based on my 86 pickup. Non turbo, with C series calibrated injection pump truck geared with 3.08 and 700 trans.

I vote for Non turbo 6.2L

I'ts all in the gears and a light right foot ;)

[DmaxMaverick]

My first answer would be N/A 6.2L, but....
There are too many variables.

What vehicle will it be in? 1/2, 3/4, 1 ton? Pickup? SUV? Other?
What type of driving is to be expected?
Towing?
Drivetrain requirements?
Power requirements?
On/off highway?
Driving habits?
Speed expectations?

The list could go on.

[More Power]

The vehicle will be a factor in answering the question as to which engine produces the best fuel economy. Also, part of the fuel economy equation is determining the intended use. We'll talk about all aspects....

Was this a trick question? :D

MP

[AndyL]

I would use a NA 6.2J stuffed in an 80 Olds Cutlass with a 700R4 and a rear gear ratio tuned for 1700 RPM at 70 MPH.

[dieseldummy]

I would say it doesn't matter what engine. My answer is any engine with the IP calibrated to only deliver XXmm3 of fuel. Then it can only burn so much fuel as well as only have so much attanable HP.

[catmandoo]

well just from my experiences,my old 84 c10 with 6.2 and 700r4would run about 25-26mpg,and my 92 c1500 with n/a 6.5 with nv4500 ran a high of 27mpg on a half dozen occasions.i have since put my banks turbo on it and turned the pump up and man lots more power,yet i have still pulled 27 on occasion.they both use 3:08 gears.so if i had to chose i would probably go 6.2 with the 4500.but i really don't think it will be much more,i've been thinking of a way to hit 30mpg.but just haven't got there yet.

[grape]

lots of compression, hardly any fuel delivery, small T3 based exhaust housing and wheel with about 6 pounds of boost from a T04 H3 inlet wheel. That's enough inlet air for around 180 hp, yet fuel delivery would probably be around a stock 135-140 hp c code engine. Wouldn't matter which engine as long as it had the correct pre-chambers. I'd also put it in one of our out of date bodied craftsman trucks......could weigh in at just over 3K pounds. And it deffinately needs a T56 from a late model camaro or firebird.

[More Power]

There are 3 or more scenarios that we'll discuss concerning engine/vehicle requirements and maximum fuel economy.

1- Scenario #1 - Fuel economy supercedes all other prorities for your fullsize street legal pickup/Suburban.

2- Scenario #2- You run at 75-mph on the Interstate most of the time in your pickup/Suburban without a load.

3- Scenario #3- You use your pickup/Suburban for all sorts of family and work related driving, including towing the 7K family travel-trailer a few times a year.

MP

[NH2112]

Well for scenario #2 I'd use a 1/2 ton with OD tranny and gear it so that when in OD and at cruising speed I'm turning about 1800rpm. That would put you at about 55-60mph when turning 1800rpm in direct so your mileage while not on the interstate wouldn't suffer too badly.

[dieselhumvee]

How about a budget fuel economy buidup. I vote for a 6.2 na in an 70's el camino with 2.56 gears and an overdrve trans.

[convert2diesel]

To answer scenerio 3, I have been driving the Buick Roadmaster wagon conversion now for a little over a month and this is my initial experience.

The conversion is a "J" code tested used engine from Diesel Depot with a Hummer intake, 3 in single exhaust using low restriction muffler and resonator. 3.23 gears through a 700R4 (gasser torgue and tranny...soon to be upgraded to full diesel specs before I do our yearly sojorne to Florida in April with the Coleman).

Drives in the city like it's butt is on fire (certainly gets alot of suprised looks) and still gives me 22 - 25 MPG (CAN), about 18 to 20 US. If I can ever get the return lines from leaking, maybe another 10%???

2 100 mile trips on the highway at 70MPH gave me 30 and 34 MPG (CAN) respectively. Will have to change the timing gears and chain over the holidays and that should allow me to set the timing correctly. Once the temps get over 30 degrees F,with the proper timing and using 100% bio-diesel, I don't think 37 MPG is out of the question.

Car was designed to tow and is spec'd for 7,500 lbs. The 6.2 may be a little light for this kind of wieght (will see. Friend has a 7,000 lb. Airstream that I'm going to try when the snow clears). From what I've seen to date, the current setup should have no trouble what so ever with my 2,500 lb Coleman.

The thing that really impresses me is how smooth and effortlessly this car performs. With it's old gasser, anything over 60 MPH and this thing was humping. Add the trailer and you'd think I'd just stabbed it's mother. With the 6.2 I have a hard time keeping it under 70MPH on the highway and with the exception of the diesel rattle (music to my ears, bone of contention with my wife), it is not any noisier then the gasser.

Will keep you appraised of further testing.

Bill

[ 12-19-2004, 06:11 PM: Message edited by: convert2diesel ]

[dieselhumvee]

I like the idea of a 6.2 or 6.5 in a car, the mileage potential is much greater than in a pickup. Not to mention you can use a big, rear heel drive GM full size 70's or 80's car that wil provide a lot more room than any VW diesel car and be much less expensive on maintenance than a mercedes diesel. I would like to have a full size GM diesel car for work and just everday driving, and an Elcamino would be even better, I could pick up stuff from home depot or haul other light loads with ease.

[catmandoo]

convert what years your roadmaster?

[convert2diesel]

DieselHumvee and Catmandoo:

I am trying to build up a conversion "Kit" for the 91 to 96 "B" body GMs. Peggy Sue is a 91 Roadmaster wagon with the trailer towing package, including the factory air shocks (ergo the single exhaust...why pray tell would they mount the compressor under the car where it gets all the road spray??)

This chassis is basically the same as the "A" bodys built since 1978 and our kit should retrofit any of these cars easily. Probably there is more room in the "A"s. Hope to have a website up and running early in the new year.

Oh and by the way, a full size wagon with the rear seat down, allows you to carry a 4x8 sheet of plywood with the gate up thereby negating the need for an Elcamino, though that would be a great conversion. The air shocks are good for 750 to 1,000 lbs.

Bill

[Brianlar]

All things being equal, a 6.2 NA, should give the best mileage.

[john8662]

I think in all fairness for this excersize MP is referring to using a 6.2 for best mileage in a vehicle that came factory equipped with a 6.2L. Mainly Gm Pickups, Blazer/Jimmy, Suburbans, and vans.

I think that most follow Scenario # 2 in that we measure the fuel mileage on the interstate going between 70 and 75MPH. I know I for one, never look at mileage in town or in mostly mixed traffic because It'll be bad no matter what. When it needs fuel, I put it in.

But when traveling on the highway, I always measure fuel economy, this helps me tell the condition of the engine and or powertrain.

I've seen a best 24MPG on the highway with my rig, but I couldn't get that the last trip I took, it was a mere 19.

Things I would do to improve fuel economy:
-Cruise Control
-Proper Sized Tires for Gearing (insure accuracy of miles driven)
-Max Air flow (make note of Black smoke)
-High Gear Ratio (but matched for speed and engine power output)
-Probably best Fuel Economy at 1900 RPM
-Total Weight Of Vehicle (good bye tool box full of junk).

[cschneider]

I am missing something here? All things being equal a turbo diesel will produce better fuel economy than a N/A engine. Efficiency is improved in a turbo engine becuase the fuel is more efficiently burned in a compressed state and the ingition of the fuel air mixture is more powerful. If the injection pump delivers the exact same amount of fuel in both engines, the turbo engine will produce more power per stroke than the N/A engine, correct?

[G. Gearloose]

nope, not if you only need 30 hp to roll down the road.

[20050420|7|006071|000022|69.19.2.78]

so hello,

When i have a lite foot, i can come to 7.5 liter diesel on 100 kms, in my nova 6.5 NA/4L80 combo with 2.73 gears, i think it can be better with a bigger exaust, timing gears and k&n airfilter. :cool:

[catmandoo]

convert,i'd like to check those out when your done.those buicks are some cruisers.

[NH2112]

I think the turbo will get slightly better fuel mileage, if all other factors are the same, because it completely burns more of the injected fuel. Add propane and you completely burn about 95% of injected fuel, as opposed to 80% or so in an NA engine. More injected fuel being completely burned = more power at a given throttle setting = less throttle needed to produce x hp from a turboed engine (and propaned, perhaps) than from an NA engine. Obviously that's "theoretical" and what you see in the real world will be different, but not too far off.

[More Power]

Scenario #1 -

smile.gif dieselhumvee and I think alike....

Just about any year El Camino would be a real sweet fuel economy rig. An N/A 6.2 or 6.5 that was professionally rebuilt, balanced, gear drive timing set, 6.2L "C" series cylinder heads, port matched and running a DB2-4911 and matching injectors defueled for N/A use. Dual 3" mandrel bent exhaust with crossover pipe and free-flowing mufflers. These car/trucks weigh about 3800 lbs and have a better drag coefficient that a truck/Sub. 30-mpg could be possible with 3.42 gears and a 700R4.

Otherwise, a 2WD 1500 series pickup or Suburban, lowered a bit, and geared with 3.42's or 3.73's and a 700R4 should deliver fuel economy in the mid 20's with a non-turbo 6.2 or 6.5 - maybe a little better if driven at no more than 65-mph. The 1982 GMC K1500 4x4 I owned would deliver 24-mpg if driven at 65-mph or less. Alltime high was 27 at 55-mph.

http://www.thedieselpage.com/images/62BSFC.gif
Fuel consumption rate for an N/A 6.2L diesel.

An N/A engine is more efficient than a TD in light load applications. Pushing exhaust through a turbo and its more complicated exhaust manifolds takes energy. At lower power requirements, a non-turbo is more efficient. I'd stay with the 21.3:1 pistons. smile.gif

MP

[ 12-22-2004, 02:32 PM: Message edited by: More Power ]

[john8662]

Heads?

Using C series pre-cups, but I wonder if using the 82 Model heads would yield better fuel economy as they have largest valves?

[dieseldummy]

Ponder this, '86 or so Lincoln town car with a 700r4. Late model 6.5 with 25:1 compression ratio, '82 heads ported and polished, splayed mains, fuel rate set to "C" engine specs supplied from a DB-4 pump, injectors set to pop at 3000+psi, free flowing exhaust and intake. With the high compression ratio comes thermal efficiency and fromt the DB-4 pump comes the capability to supply high injection pressures for extended periods of time which in turn raises effeciency by better atomizing fuel spray. The splayed mains would help the block better cope with the high stresses involved with 25:1 compression and the '82 heads as John mentioned have the bigger valves capable of flowing more air. Not only would you have a car with all the creature comforts, but a drivetrain capable of delivering 30+ mpg...

[More Power]

I owned a 1982 "C" 6.2L diesel that I had rebuilt. The largest valves came a couple model years after the introduction of the 6.2 in an effort to improve power. GM abandoned the large valve heads because of a much higher likelyhood to crack. I've seen a couple sets of large valve heads, and I sure wouldn't use them. I'd leave the compression ratio at factory specs. The head gaskets are the concern here with higher CR, plus I don't think you could raise CR much because the 21.3:1 piston protrusion through the cylinder head deck is already taking up all of the room.

I like the idea of a DB4.... :)

To get max fuel economy, think low vehicle weight, minimize drag force, maximize engine efficiency and drive at efficient vehicle speeds with appropriate gearing. Got to stay below 65-mph. With a light vehicle, slower speeds and correct gearing, a non-turbo 6.2/6.5 built as was mentioned above would get you the very best fuel economy.

MP

[moondoggie]

Good Day!

More Power: Is there an article and/or project in the future here? Since mpg is my only hobby, my interest is VERY high, although my ability to duplicate anything you might do is limited.

I'll be watching this topic.

Blessings!

Brian Johnson, #5044

[More Power]

Moon... Might... I have lots of photos of special stuff that would work for a fuel economy article...

2- Scenario #2- You run at 75-mph on the Interstate most of the time in your pickup/Suburban without a load.

Wind drag increases exponentially, with drag becoming an ever more increasing factor above 65-mph. At 75, you need a turbo. The efficiency loss of pumping exhaust through a turbine is now overcome by the increase in power and efficiency offered by a turbo when operating at the higher power requirements of 75-mph.

Still, a 6.2/6.5 built as the above N/A 6.2/6.5 would apply, but we simply add a turbo and a single 3" mandrel bent free-flowing exhaust system. Gear the vehicle for 2000-rpm at 75-mph, and shoot for somewhere in the vicinity of 3-5 psi boost pressure at 75-mph on a level highway.

As mentioned above, wind drag is significant at 75-mph. Anything you can do to decrease drag will pay big dividends in fuel economy. Under-bumper air dams reduce drag, as does lower vehicle ride height. Lose the exterior accessories (like bug deflectors, etc.) and run narrow radial highway tires with maximum air pressure.

Differentials..... Open diffs have lower drag than limited slips.

MP

[john8662]

The 65MPH theory is true, thats when I got my best MPG at night traveling doing the night time speed limit of 65.

[More Power]

A few facts and trivia concerning my 1982 6.2L GMC K1500 pickup.

When I first got the truck, it was four years old. The previous owner had gotten tired of fixing the 700R4 and had installed a TH350 3-speed auto without overdrive. I drove the truck in that configuration for about 9 years, which roughly corresponded with the relaxing of the speed limits.

Once the speed limits were removed here in Montana, I quickly learned not having an OD was a problem. So, I had a performance built 700R4 installed. I just wished I'd done that years earlier. The improvement in driving pleasure was astounding.

http://www.thedieselpage.com/images/alta.jpg
circa summer 1988 at a remote F/S campground in western MT.

This truck had 3.42 gears and produced 17-19 mpg with the TH350 at about 60-mph. Once installing the 700R4, fuel economy jumped to 22-24 mpg. When kept to no faster than 65, it would deliver a consistent 24-mpg.

Then I added a Banks turbo. Fuel economy actually dropped to a consistent 22-mpg, but who could resist not using the extra power. I suspect if driven exactly the same, fuel economy may have been a little closer to when N/A.

Speed hurts.... At 65, I saw close to 22 or a little better. On one 700-mile Interstate round trip between Missoula, Montana and Billings, Montana, I drove the 6.2TD GMC at 80-85. Fuel economy on that trip dropped to 17.5-mpg. Was fun though.... At that time, the "Reasonable & Prudent" rule applied to MT's Interstate speed limits.

Seemed prudent.....

MP

[ 12-21-2004, 02:04 PM: Message edited by: More Power ]

[grape]

6 speed manual is in order most deffinately. I would also like to have the rear end out of the vehicle to put on my fixture to make sure it is exactly true. As the come from the factory they are within an 1/8" which in our world at 180 is unacceptable. There are also a few various things I'd like to do to the ring and pinion and the axle bearing surfaces.

[G. Gearloose]

I concur the manual OD trans. The 700R is efficient but not tops.

Could a 6.2 be stuffed in a late model Camaro?

[convert2diesel]

I too have spent a great deal of time trying for fuel economy, using various engines, mostly to allow me to continue driving my "Yankee Tanks" without draining my bank account.

One of the first things I had to wrap my head around was I was not trying for peak horsepower, but "effective" use of horsepower at the speeds the engine would be run at. One of the great things about diesels is that they are "naturalized", meaning that at part load they are over aired and the amount of fuel directly effects the power out put.

In designing an engine for peak horsepower, you are trying to cram as much air fuel mixture into the combustion chamber as possible, while still allowing the combustion process to proceed as efficiently as possible. Ergo long duration cams, turbo chargers, high flow exhausts etc. When you are designing for fuel economy, then what you want is to produce the most efficient burn at or close to, the peak torgue RPM of the engine. That is how industrial engines are designed. In our case that is 1,800 RPM. Now it becomes a question of how much horsepower you require to operate your vehicle at a given speed.

From an efficiency standpoint, the 6.2/6.5 is not a stellar performer compared to most other diesels but it does do an decent job in the power/wieght category. Fuel consumption for this engine starts at .42 lbs/SHP/Hour for the economiser and tops out at .47 lbs/SHP/Hour for the last variant 6.5. In industrial terms, that is god awful, as the engine manufacturers are consistanly producing engines in the .33 to .35 area, with some of the huge ship engines down to .28. In order for us to achieve these figures, a major redesign of the engine and fuel system would be required.

That doesn't leave much that we can do with the engine itself to increase efficiency, other then to gear it correctly to allow it to operate at it's most efficient speed. MP corrected this when he installed the 700R4. He just dropped the RPMs down closer to that magic number of 1,800 RPMs at highway speeds. Increasing or decreasing the the amount of fuel will just serve to increase or decrease the speed of the engine. Increasing the amount of air (turbo) at part throttle will have no effect what so ever except to increase the load on the engine and thus require more fuel. The advantage of the turbo in this case is that it flattens out the torgue curve, thus allowing for substantial HP increases at RPMS higher then 1,800. At part throttle and low loads, the engine is still over aired, so a turbo is not needed. As far as changing the compression ratio, it will always be a trade off. If we increase the ratio yes we will marginally increase combustion efficiency but the added power necessary to rotate the engine may negate any advantages. If we lower the ratio, then we would have to add a turbo to make up for the loss in efficiency. IMHO we should leave well enough alone and just do the mods to make this engine breath (and exhaust) as efficiently as possible and endeavour to run this engine as close to 1,800 RPMs as possible.

Any significant gains in fuel mileage will be realized in wieght and aerodynamics. Unfortunately the trucks that most of you operate have all the endearing aerodynamic qualities of a grand piano with the lid up. Perhaps the suggestion made previously about lowing the body plus adding some, more then cosmetic airdams, may be money well spent. But then some of the usefullness of these vehicles may be lost. Again that trade off thing!! Wieght is another thing. Most studies have shown that within reason, wieght is only a factor below 40 MPH and in climbing hills. It becomes a major consideration in day to day city driving, but on the highway aerodynamics is the great enemy.

Sorry for the long winded disertation, but I thought it would help the discussion get away from building a "stump puller" and into designing a mileage machine.

All the best

Bill

[catmandoo]

mp i noticed on my 92 with the 6.5n/a that after i put the banks on it i too dropped about 2mpg,but as you mentioned the banks seems to make the right foot feel heavy,but if i drive it at 55 religiously i can duplicate the same milage as when it was n/a.this is with maybe 1/2 to 1 lb of boost at the most,can a turbo be made to spool right off idle,or could a smaller turbo be used that would be spooling up at idle.my thinking is if i could cruise at my 55mph with 5-6 lbs boost wouldn't the extra boost offset any loss of power driving the turbo.i think thats how i want to say that!

[catmandoo]

must a been typing at the same time there,and you have a very good theory there on the turbo convert.

[More Power]

Cat, Don't need a turbo at 55-mph unless you're pulling a big ole trailer.... :D

MP

[grape]

I give up......you guys think hp is magic and not math. total amount of air decides hp, displacement decides when that power will be made (rpm), the bigger the engine the quicker target power can be attained. A turbo allows power to be made quicker with the same cubic inches as a N/A engine if the turbo is designed correctly.......guess why, cause it makes the engine bigger. And "big" turbo and "small" turbo is about as vague as saying I'm lost somewhere in the United States, can you help me find out where I am.

[dieseldummy]

convert2diesel,
I agree with what you are saying, I guess all I was getting at with the motor mods is that theoreticly some gain can be had from going into the motor.
grape,
Idealy the car designed for max fuel economy won't take that much HP to push through the air so in reality adding a turbo may add a parasitic loss on the engine by restricting exhaust flow. The only time adding a turbo becomes effective is when you have more fuel than air, and in this case I don't think that will be an issue... Sounds like your stuck in the world of big HP racing to me... ;)

[convert2diesel]

Grape:

Who P@#$%ed in your cornflakes this morning?

If in fact you are trying for maximum HP then you are dead right. What MP and Cat were talking about was making the engine more efficient at part throttle.

Not all of us are trying to pull stumps down on the farm nor are we interested in taking on the local piston heads in their HunToyIssans. We are just looking for good functional vehicles that can be operated economically.

What Cat was asking was a question of volumetric efficiency at less then optimal flow. Unfortuantely if you size (Using math) the turbine for low exhaust flow, when you do put your foot into it the turbo looses it's efficiency and effectiveness.

What MP is saying is what I am saying...namely at part throttle and low RPM "you don't need no damn turbo" Run your numbers any way you want. You'll come to the same conclusion.

Bill

[ 12-21-2004, 07:46 PM: Message edited by: convert2diesel ]

[More Power]

These are just opinions.... smile.gif

Scenario #3- You use your pickup/Suburban for all sorts of family and work related driving, including towing the 7K family travel-trailer a few times a year.

http://www.thedieselpage.com/images/65towing.jpg

This is the category that most of us fall into - to one degree or another. Let's talk about maximum fuel economy strategies for scenario #3.....

MP

PS. I had a hell of a time climbing the tree to take that photo... :D

[ 12-23-2004, 02:49 PM: Message edited by: More Power ]

[convert2diesel]

Dieseldummy:

Yes you are right. The higher volumes and pressures of the 4 piston pump do assure a better spray pattern but at what cost? The DB2 already sucks up close to 3 HP with 2 pistons. What the extra pistons would add I can only guess.

The point I'm trying to make is that the boys at GM did a pretty good job of sizing the pump to the engine in order to do the job they intended. Stanadyne states that the DB2 is available in sizes up to 25HP per cylinder (4911???). Though I doubt the head design is capable of 200 HP, it does look like Dr. Lee has come real close without a turbo. This means that the engine, if made properly can flow enough air to accept this amount of fuel without an added push.

Now back to the topic. Assuming your trucks require 25 to 30 HP to maintain 60MPH (just guessing at the numbers here) then using the formula of .43 lbs. of fuel per shaft HP per hour, then this engine will require 12.9 lbs of fuel to travel 60 miles. Based on 6.5 lbs/gallon, that gives us 1.98 gal per hour or about 30 miles to the gallon (sound familiar?)

That also means the pump (regardless of chamber size or the number of pistons) is only pumping out a fraction of it's capabilities to maintain this power level. If the pump and injectors are sized and matched I can't see a significant gain in bumping up the fuel delivery.

Just my thoughts

Bill

[convert2diesel]

Morepower:

Can we add family station wagons to this scenario?? :D

Bill

[dieseldummy]

MP, as to scenerio 3 I have to say it's all about the middle ground. 3:73 gears, stock tire size, with a 4L80E tranny or 4:10 gears, bigger tires size, also with the 4L80E. Would prefer the first. If 4x4 is a must then have it, but if you can get away with sandbags and 2wd in the winter do it. Run the '97 cooling mods with 195 thermostats in both holes. When not towing run conservative tire pressures for ride quality, but not low enough to create extra rolling resistance. When towing run them up to the max in the rear and a little higher in the front. Engine wise I say it's all about the injection system. Run a performance chip, or modified IP, but drive it like it only has the factory 180 horse power. Run high pop injectors, I have found that going from stock 6.5 injectors to stock 6.2 injectors has lost me 2-3 mpg. I will also have to add here that it has been my personal experience that the turbo has a big part in the economy equation. If financially feasible run a different turbo, or modify the stock GM series wastegate to open under low throtle conditions. Example: crusing down the road at 65 mph doesn't require 6 lbs of boost...The less restricion in the exhaust sytem the better. On one final note, I beleive that the quicker engine, transmission, T-case, diferentials, ect. come up to temp and stay within 5-10 degrees the better the efficiency of the vehicle will be.

[dieseldummy]

convert2diesel,
I agree with you whole heartedly, I was just making an attemp to think outside the box. :cool: The only reason I suggested the DB-4 was for maximum sustainable pop pressure. What effect the 2 added plungers would have I don't know either. You are most likely right in that there isn't a whole lot to be gained from the motor, and focus should be on the rest of the drivetrain and aerodynamics.

[More Power]

I can usually find tech info that can either support or weaken a particular point of view.

I did a little digging today looking for information regarding whether a turbocharged or a naturally aspirated diesel engine delivered better fuel economy in light-load applications, such as our scenario #1. The following information is generic in nature, not specifically targeting the 6.2/6.5 diesel engines. However, this might be useful to help us learn more about the subject. Seems Heinz Heisler isn’t all that secure in one particular point of view either.

Excerpts from Advanced Engine Technology by Heinz Heisler

Argument for naturally aspirated:

Page 316: “Consequently, under light load and low engine speed conditions the energy released along with the exhaust gases will be relatively small and is therefore insufficient to drive the turbine assembly at very high speeds. Correspondingly, there will be very little extra boost pressure to make any marked improvement to the engine’s torque and power output in the low-speed range of the engine. Thus, in effect, the turbocharged engine will operate with almost no boost pressure and with a reduced compression ratio compared with the equivalent naturally aspirated engine. Hence, in the very low speed range, the turbocharged engine may have torque, power outputs and fuel consumption values which are inferior to the unsupercharged engine.”

Argument for turbocharging:

Page 343: “Turbocharging diesel engines can reduce the specific fuel consumption from about 3% to 14% in the engine’s speed range. The reduction in fuel consumption becomes more marked as the engine’s load is reduced, as can be seen in the family of constant load (b.m.e.p.) curves ranging from

[jbell]

MP:
THANK YOU for the fuel curve, it was one of the first things that I wanted to see when joining this board.
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002952#000000

If anyone is interested in the cummins 4bt fuel curve (the motor in gm bread trucks) I can post it. But I can tell you that at redline, it's only .40, and @ max torque, it's .37 --- Much better than our 6.2's. So the best method of getting better mileage is to use a gm / cummins 4BT. (grin)

I also started a thread on this on the 6.5 side.
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=006710#000024

From my investigating, it appears that larger, heavier duty transmissions absorb more HP, leading to lower fuel economy. Also RP ratio, the coating (if any) on the RP as well as the oil used contributes to loss of HP / MPG.

My opinion on max mileage (assuming you HAVE to have an auto tranny)
Stock J code 6.2 NA, 4" fresh air intake, dual exhaust, 700r4, 4.1 gears, 265-85r16, mobile1 in the rear end.

The fuel curve seems to disprove the 1800 conventional wisdom for max fuel economy, in fact the sweet spot appears to be about 2200 -- any thoughts on this???

One big unknown for me, and I've posted on this as well, http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002850#000004
is a dual exhaust on a NA 6.2 in terms of fuel efficiency. It is common knowledge that a properly tuned balance pipe, creates a vacuum on one bank from the exhaust pulse on the other bank. This in effect creates a turbo effect (Think 2 cycle motorcycle effect), without wasting the energy spooling a turbo. The effect is very rpm dependant, but if it were tuned to the cruising rpm, it would dramatically increase volumetric efficiency, and in theory MPG. Thoughts?

[farmerherb]

I know that my 83 NA 6.2 conversion won't get out of it's own way. Yet it gets 25mpg. Everyone I heard, that has put a turbo on a 6.2 confess they can't help pressing harder on the acc. pedal. I know that kills mileage. I own 3 VW TDIs they all have intercoolers and turbos why? Did VW have alot of parts laying around? I've been told you can't run a diesel engine lean. So why not cram lots of cool air into the engine and a little fuel? I knew a guy who had a banks on a 85 c1500 pickup pulled a motorcycle trailer across the country, got 28mpg. I may not like the mpg of my van with a turbo but I'm going to try it. I had driving it in traffic!

[convert2diesel]

Along the lines of gearing has anyone had any experience in building up a THM350C? When researching the powertrain for the Buick, with the goal of keeping the engine in the 1,500 to 2,100 RPM range, I was tempted to go with the 400 coupled to a dual range, add-on overdrive. This would give me the advantage of an overdrive plus the ability to gear split all forward gears when towing the trailer.

While 6 forward gears was enticing, the thought of heat build-up and efficiency loss through a non-lockup convertor made me back-off that idea. While researching build-ups for the 700R4 I found that many of these places also did 350s for the throttle jumpers. Maybe if you could build one of these strong enough and couple it to a low stall lock-up convertor and then run it through the overdrive unit, the same results could be realized.

Is this viable?

Bill

[Stage1]

RE: Cylinder Heads

Enjoying this thread, as I have a project Blazer in the planning/parts gathering phase, with this theme. I would be interested in a follow-up discussion on what is the best cylinder head build-up for 6.2 NA engine. New to diesel/6.2.
(A little bit of experience w/ gas engines)
Why was the "6.2L "C" series cylinder heads" recommended above? Assume this is any "C" engine head? Why not "J" series heads? Assume their are many areas we could discuss,e.g. best valves, valve preparation, seat angles, throat cut angles/depth, head porting tips ( critical areas to work/ areas not to touch), valve lift vs power development ( what lift range effects power most). I am ready to turn on the flow bench and get the grinder cutting!
thanks,
Les

[More Power]

"C" series cylinder heads were designed at a time when fuel economy was a huge factor in marketing GM full-size pickups. Mostly, this involves precups with the smallest ports. 6.5TD heads could be rebuilt using "C" cups. Dr. Lee's Avant 6.5 comes very close to the ideal fuel economy engine.

Saw a discussion about the NV3550 the other day on TV. This is an aluminum cased 5-speed, rated for 450 lb-ft of torque. This might be a good way to go for the gear-bangers out there, to use for a fuel economy rig.

Automatics with a locking TC come close to the efficiency of an OD manual, but the manual is best.

MP

[jbell]

Here's the typical gm bread truck cpl.
http://www.christ-our-savior.com/web/Scan10006.GIF

[jbell]

some math, assuming a typical suburban, that gets 20mpg at 60mph, and gearing that has the engine running somewhere between 1800-2400.

At 60mph getting 20mpg, that's 3 gallons in an hour * 7.1lbs/gal for #2 fuel = 21.3lbs of fuel / hr.
.41lbs/hp*hr / 21.3lbs = 60hp*hr used for a gm6.2
.37lbs/hp*hr / 19.22lbs = 60hp*hr used for a b3.9
cummins b3.9 @60mph gets 22.2mpg, that's 2.7gallons in an hour * 7.1lbs/gal for #2 fuel = 19.22 lbs.

So, what't that tell us? Even a direct injection cummins, only gets us 2.22 mpg bump, assuming the same load. The big thing to look at, is why does it take 60hp to move a typical suburban down the road? If you are looking for max economy, looking at improvements in the engine is nickle and dime stuff (with the exception of using an electric vs. mechanical fan), looking at reducing the power requirements (reducing driveline losses, rolling resistance losses, and aerodynamic losses) gets you much further down the road.

Anyone done any airdam testing on mpg on a typical suburban?

[moondoggie]

Good Day!

convert2diesel: I thought Jet offered a 700R4 warranted to 440 lb/ft, which would more than cover this application. This would provide the lockup TC, which would seem better for mpg than any non-lockup TC. I've also heard it said that the 700R4 has lower 1st & 2nd gear ratios than the 400 or 4L80-E, which, while not being as elegant as gear splitting, would help with towing and/or hill climbing. The looser TC allowed by having lockup would help here too.

I really know nothing about trannies, just parroting what I've heard elsewhere. I know you folks will fix my errors.

Blessings!

Brian Johnson, #5044

[jbell]

http://www.airtab.com/

This looks like the best bet for cleaning up the aerodynamics of a suburban. Hey it works for tractor trailers, why not a sub?

[Stage1]

MP thanks for the reply on the "C", at least one more question, what time period was this? mid to late 90's.
Jbell, the fuel, torque, HP, vs RPM curves are outstanding!! Loads of good information.

About lowering HP needs, the 10 bolt rearend has the lowest HP lose, better then 12 bolt, 14 bolt is not even close. For the 10 bolt rear you can use aluminum drums from Trans Ams, Formula, certain Buick Gran Nationals, and a limited number of station wagons that came w/ this rear. Lowering the rotating weight of drive train helps mileage, and more then other weight in the vehicle. I think it may be something like 1 pound from drivetrain rotating mass is equal to 4 pounds of static vehicle weight. Therefor tires, wheels, drive shaft, transmission and differential rotating parts are all potential areas for improving milage by reducing their weight.

Another area is friction in the power train.

Tire design and size are also areas of measurable improvemnent as mentioned above.

For me the biggest improvement would be to get rid of the hills here in Kentucky!

thanks for the information,
Les

[More Power]

The 6.2L "C" series diesel engine was produced from 1982 through 1993. The recent listing of the "Fuel Miser" 6.5 engine by GM Powertrain is the most current rendition in design configuration(though lacking some emissions control devices).

Regarding scenario #3, needing to tow occasionally means the engine needs a turbo. If only light trailers and for infrequent towing duties, 3.73 gears, "C" cups, and a DB2-4911/6.5 injectors. If towing more or more often, 4.10 gears and possibly TD cups. Based on lots of discussions with lots of owners, there appears to be about a 2-mpg difference in cups alone.

If towing more than 5-7K, and doing it often, I'd then go to an 18:1 engine and all the other stuff necessary to keep things cool and make More Power, which is now beyond the scope of this thread.

MP

[grape]

if you are going for max fuel milage, with the least possible drag, who are you going to have align the truck.....Sears? I would suggest NOT letting anyone with a computer alignment machine touch the vehicle in question. Those things are the devil and assume the rear end is square to the centerline of the lower front susupension pickups. But this suggestion is only if you decide to get serious about this deal.

[CareyWeber]

Originally posted by grape:
if you are going for max fuel milage, with the least possible drag, who are you going to have align the truck.....Sears? I would suggest NOT letting anyone with a computer alignment machine touch the vehicle in question. Those things are the devil and assume the rear end is square to the centerline of the lower front susupension pickups. But this suggestion is only if you decide to get serious about this deal. This seems like a worth while thing to do for best MPG.

Someone said once here that mirrors are a big factory in fuel mileage.

I think tire pressure is big deal.

Carey

[Stage1]

MP,
Thanks for the additional information on "C" cylinder heads, are these heads the same or different from the "J" engines of those years.

Have five CUCV Blazers w/engines which I will us to build my project Blazer. They all have low mileage 25 to 45K miles and the model years are 83' and 84'.
thanks,
Les

[dieseldummy]

The heads are the same, the only difference is the precups, which are interchangable...

[dieselhumvee]

I now get 13.5 MPG in my Hummer. With the price of diesel and my being a Hummer owner on a budget (talk about an Oxymoron), I would like to improve it's mileage. First off is to ditch some weight, I think I can get rid of 800 pounds by swapping the hardtop and steel doors with a military soft top and canvas doors. I now get 13.5 MPG so say the weight drop gets me 1 MPG, I would then be at 14.5. I like the idea of C precups and some head porting. I am confident that any power loss from switching to C precups from J precups would be cancelled out by the weight loss. So if I gain 2 MPG with the C precups, then I get to 16.5. My goal is 18 in a 6000 pound Hummer, right now it is 6800 with hartop.

I may experiment with the airflow tabs from http://www.airtab.com/ The hummer is atrocious when it comes to airflow, one of the worst aerodynamic designs ever, so I could pick up a little there.

Does anyone know if the diesel depot cam is worth any mileage improvement?

I am also thinking of more drastic weight reduction including removing the trailer hitch, factory airlift hooks and brackets, swapping the steel rims and runflats with aluminum wheels, sythetic winch line instead of steel, and swapping the heavy duty rear bumper with a light duty one. I think the additional mods will be worth 400 pounds of weight reduction, so I may get to around 5600-5800 depending on what I put back in like tools, etc. The 6800 is with spare tire and a few tools, but I will be adding more tools.

[jbell]

Forget ditching weight in attempts to get mileage. I have a similiar beast in terms of total weight. (85 3/4ton 'J' code suburban with 4.10 gears) With the tire size I had, I was right in the exact same ballpark you were in terms of final ratio. 15mpg was the best I ever got, and the motor was SCREAMING down the road. Swapped in a 700r4, and now get 20mpg at 75 mph. The best and only way for you to better your mileage is to get the rpm's out of the stratosphere. (That and a fastback, slanted soft top) The 700r4 did 2 things for me, 1 was a lockup torque converter, and the other was a .69 overdrive. Both contribute greatly to my reduced engine rpm's. I'm still in the mid 2000's driving down the road, but if you look at the fuel curve earlier in this thread, fuel mileage doesn't really go bad until after 2400.

My thought is to leave everything else alone, don't worry about cam or any of the other engine options, try to find some way of getting an OD trans with lockup, you'll easily hit 18. Not sure if you can get a 700r4 built up with a 32 spline output shaft or a spud adapter to mate up to your xfer without changing overall length. Call AdvanceAdapters.com or Novak.com -- they are the best in the business of making engine / trans / xfer cases mate up.

[jbell]

should have checked earlier, your np242 xfer can accept either a 32spline input or 27spline. If you are interested in a built up 700r4, here's the drill:

1. you'll need a new flexplate, the th400 and 700r4 flexplates are different.
2. you'll need the hard to find tvcable bracket that bolts to the back of the engine, and the tvcable extension rod that's easily found from gm.
3. you'll need a 89 or later 'K' case built up 700r4 with lockup converter and all the goodies (beast sunshell, etc...) I happen to know maddoglou makes a good transmission, not sure who else does.
4. you'll need the 83-91 suburban 700r4 diesel tv cable.
5. you'll need the 27spline female input for your np242 xfer. (check with advanceadapters to see if you need anything else)
6. you may need to make modifications to the crossmember location / mount, not sure on H1's. Overall length should be within 1/2" however.
7. You'll need your trans set to lock in 3&4 internally, run +12 to it through a brake pedal interrupter switch, ditch the vacuum modulator lines, and the kickdown switch from the TH400.
8. on mechanical speedo gears, there should be something that works for you, don't ask gm, just find a gear chart and get the speedo housing , gear that works out correctly with your 5.24's and 44" tires.

Your existing oil cooler lines will just bolt up -- no worries there.

On my application, my sub went from dog slow to much faster than average traffic. From so loud I couldn't stand it, to acceptable, and from 14-15 to 20mpg. In fact, I still have all of the TH400 stuff I pulled out -- anyone interested? TH400 spells bad mileage as far as I was concerned with the gear ratio that was present in my suburban.

My guess is that you can do all of this for about $1200 -- since you were talking cam, precups, and some other serious stuff -- it should be well within budget.

Good luck

[convert2diesel]

Jbell:

In regards to your observation of better fuel mileage at 2,100 RPMs, I ran across an older power curve published internally by GM for their service people. Sure enough, these engines have their peak torgue and lowest fuel consumption at 2,100 RPMs. Meaning you are probably correct if the gearing translates into 50 to 60 MPH.

If someone could instruct me on how to post directly into this site without first posting it elsewhere, I would be happy to scan this chart in.

Was talking to a guy the other day who does cold weather performance testing for John Deere and he said not to take the specific fuel consumption figures too seriously as these figures are taken at WOT. Very informative if you are designing stationary engine applications but not much use in automotive applications. To his knowledge, no-one does comprehensive flow testing at part throttle unless it is required for diagnostic reference, or to set up computer controls. Something to do with "base-lining" the tests.

Bill

[grape]

if somebody will do this little project I'm sure I can convince our engine builder to let us use his $3400 fuel flow meter on the test vehicle to take readings at a steady speed.

[convert2diesel]

Grape:

I feel the same test could be done using a chassis dyno and some graduated beakers/portable scales. That way we could determine the consumption using known perameters. The mechanical losses could be determined based upon load and the actual engine output could be compared to actual fuel useage.

I have no idea how the fuel delivery is effected at lower dome pressures and or IP RPMs. Another factor is where the advance piston is situated and how that effects the overall efficiency of the engine at light load on the mechanical pumps.

I had some idea I was going to go to southwest Texas for my holidays in April, and would gladly donate the bio-Buick for the test, but would prefer to use a fresh engine and fuel system to get a more accurate base line to work with.

Bill

[twaddle]

Hi Guys,
I've used 4x4 pick ups with 6.2's fitted with both manual and auto gearboxes, done several hundreds thousand miles mostly carrying tools and parts for work (I repair Cat Equipment throughout Scotland).

Several times a year I pull trailers with up to 4 or 5 tons on them. (yes well overloaded)

If I was going for economy and pulling power and running light use I would definately go for a 5 or 6 speed manual. 235/85/16 tyres , use a diff ratio that suits your average use.
The main thing is the manual gearbox, to get best economy you need to keep the engine working on its torque. I've always found that a good torquey diesel engine can be worked on the torque better with a manual because you can hold the gear ratio required whereas a auto box always has slippage when you don't want it or it changes down.

Just out of interest, at the moment I use a ex military K30 (M1008) pick up with a "J" spec 6.2, 3 speed th400(no lock up torque or O/D) and 4.56 diff ratios on 285/75/16 tyres.
On a good day it gets around 17mpg (average 15), that's to the US gallon, even with a 4 speed manual I would probably get over 19mpg. Now if I only had a O/D manual, better economy, quieter.
Thinking of fitting a 700R4 as they are getting pretty good value for money for a rebuilt unit and easy to fit.

Ah if I only had the time and money to build the dream trucks ........

Regards

Jim Twaddle
Biggar, Scotland.

[jbell]

convert2diesel:
I'd love a copy of the fuel curve you have. can you send it to my gmail account? (jbell.louisburg@gmail.com)

Yes I understand that fuel curves are typically WOT, and that fuel consumption is not exactly linear at a specific rpm under varying HP output.
(The lower the specific output, the more fuel/hp that's required as engine friction / pumping losses don't change) So when I did the calculations above, and came up with 60hp, I know it 's really a little less than that.

However, in defense of the fuel curve.....
It's scary on a stationary industrial applications using cummins motors how accurate the fuel curve is. (The farm pumps water, 24hours a day, 7 days a week during the summer and we know the HP required down to within a single HP, as we have had cummins diesel, and 3ph electric on the exact same well, and KwH will give you an EXACT HP draw.) I'm always within 10% and sometimes less than 5% different than the fuel curve, (depending on engine condition) on consumption, regardless of the fact that I'm pulling at about 60% vs. WOT. (That's using an water/air chiller to maintain constant charge air temp) I understand that fuel curve can't be trusted down in the 10% - maybe 30% range, but with a NA 6.2 only making a hair over 100hp @ 2000rpm, I think we are far enough up on the %of WOT, that the fuel curve is meaningful.

[More Power]

Fuel curves are very useful to compare engines in stationary applications, but the water gets murky once we try translating that to "miles per gallon".

Vehicle weight, vehicle rolling resistance, drag coefficient, elevation, engine tuning & overall health, driver skill & technique, and many other factors affect mpg, that are not necessarily reflective of a bmsfc chart when considering fuel economy in a motor vehicle.

MP

[jbell]

MP:
You are very correct in what determines fuel mileage -- HP requirements. What we do to our 6.2 engines should make very little difference in mileage. What we do that affects how much HP we require makes a HUGE difference in mileage. In the earlier post, I used a fuel curve to 'back in' to HP used -- I find it's useful to see if I'm even in the right ball park when comparing fuel consumption vs. estimated HP requirements.

60hp to move a suburban down the road at 60mph is not in the ball park, it should be down in the 30 to 40 hp at most. So what's that tell us? To me it says that the average suburban is wasting about 20 hp somewhere. We find out where, and we get better mileage.

I personally get 20mpg @75mph, why? With 4.10 gears on a 3/4 ton suburban -- my rpm's are too high, with the tall tires, it's too high off the ground, and it's an 85 with a 41 gallon tank, meaning, it weighs alot. I don't know what the right lane is, and letting people pass me, is, well, insulting..... (meaning I have a lot to learn to get max mpg on my driving skills.....)

(I did drop it to 18, running to western kansas over Christmas bucking a 30 knot headwind....)

Did the 2" lift blocks I put in the rear to get rid of suburban sag, help my aerodynamics? Did going to a 700r4 vs. a TH400 really lower my HP requirements that much? I'm running stock 155hp pump tuning,stock 'j' precups, the low pop 6.2 injectors, nothing special on the intake / exhaust, the 'inefficient' 14bolt rear axle -- yet I consistantly beat later model 6.2 / 6.5's by a huge percentage on mpg. why?

[More Power]

jbell, For whatever reason, your engine and drivetrain are above average in efficiency. No two engines and fuel systems are exactly the same, some are better than others to one degree or another.

And, I suspect your driving ability is above average when it comes to fuel economy. Some people are more intuitive than others when it comes to driving efficiently. Gearheads and those who perform their own maintenance generally do better because they have a sense about their vehicle that others might not have.

Fuel quality can also affect fuel economy.

MP

[moondoggie]

Good Day!

convert2diesel (or others): Was my 23 Dec post on-track or not? I don't mean to be a pest, but I was kinda interested to know if I'm out in left field on this or not.

TIA & Blessings!

Brian Johnson, #5044

[jbell]

moondoggie:
I think you are right on the money on the benefits of a 700r4. I personally had HUGE problems with them in the 80's (went through 6 of them behind a 2.8l gas -- biggest piece of @#$@#$ I'd ever seen.)

However, as with all things mechanical with time and effort, they get better. I know dieselhumvee may not like the idea of a 700r4 in his H1, but consider that a 4L65 is what is in the H2 that is similiar weight, and it lives behind whipple supercharged 6.0l gas motors with no problem. A 4L65 is nothing more than an electronic 700r4 with a couple (not all) of the aftermarket upgrades to support 380ft.lbs. That's up from 360ft.lbs in the corvette 700r4. An aftermarket 700r4 can actually withstand 500ft.lbs max with all of the goodies available.

It is the cheapest easiest upgrade any 6.2 with a TH400 can do. And one of the few upgrades that will actually pay for itself with fuel savings over its life. (I've already saved about $500 over 16,000 miles, and I got my 700r4 off of ebay for $125 from a guy with a rusted out 89 diesel burb, I added a couple hundred bucks to it for strength parts -- so I'm still ahead of the game) And as MP said in an earlier post in this thread -- "If I'd known the driving improvements it would make, I'd have done it years earlier."

In comparison, a TH400 is commonly rated at 450ft.lbs, so you can actually 'upgrade' to a higher torque handling capacity with an aftermarket 700r4.

Also, lockup vs. non lockup is night and day for mpg.

The 3.06 1st gear and .69 OD makes it the widest range OD 4 speed auto available. Above all, 6.2 diesels need gears to keep the rpm's happy.

As a completely irrelevant piece of information that burns my @#$#@$ -- the (it shouldn't have the name jeep on it) 2.8l diesel that is being put in the new jeep liberty makes more HP and Torque than our NA 6.2l........ Upgrade for the H1????

[Dan Wilson]

Hay guys I have done 2 62 car transplants. Both to real good on mpg. The first one was my 82 fleetwood caddy. It had a 5.7 diesel. I took it out and installed a J motor. I gets 21 around town and 29 on the intertstate. The second is a 81 gan prix that had a 5.7 diesel. Installed a 6.2 c motor and 700r4 with 3.08 gears. gets 27 around town and 35 on the interstate trips. I love both cars.
Dan

[More Power]

Click here for the all-time best fuel economy for a 6.5L N/A powered vehicle. (http://www.thedieselpage.com/readers/vet.htm)

I couldn't bring myself to do that, but it does demonstrate what gearing, low vehicle weight and low drag can do.

MP

[convert2diesel]

Moondoggie:

Yes you are correct. There has been lots done to make these trannies more durable, and to allow them to standup to some incredible punishment. For an overdrive tranny that doesn't need electronic assistance to operate (with the possible exception of the lock-up) it would fill the bill for most use.

What I was trying to accomplish was incorporating the concept of "gear splitting". In an attempt to use this engine in it's naturally aspirated state to tow more then a light boat trailer.

It is very important to keep this engine within a very small torgue band of 1,600 to 2,200 RPMs. While this is possible with a 4 speed (8 speeds with aux tranny), the resultant double overdrive is way too low at highway speeds. If I go to an underdrive, the first gear under could be used to pull stumps out of the field and generally not useful.

That sent me looking for a 3 speed tranny, with a lock-up torgue convertor, that could handle the out-put of the 6.2, and then add the overdrive aux tranny.

My local guy said he could build up any tranny I want, but I was looking for anyone who had experience with the 350"C" behind our engines.

MP:

While I doubt the numbers the Corvette guy is getting, it illustrates what I was trying to get at. Namely lower the HP requirements and these engines do quite well in the economy department.

Would be very interesting to see one of these with 7,500 lbs of Airstream hung on the back :eek: . With 4 1/2 in of clearance I wonder if he could even get it into the campsite without leaving his oilpan at home.

Dan:

Man after my own. This is number four for me. Got tired trying to get any power out of the 5.7s though they did get great mileage, so am now doing the 6.2/6.5. This is the best one yet (knock on wood). Short of some logistical problems that are easily solved, it was reasonably painless. Now on to a 93 Fleetwood :D .

A belated Merry Christmas to all

Bill

[Dan Wilson]

The problem with the 350C may be that it uses the varable vacuum of the gas engine to determine the shift points. The 200C 2004r and 700r4 use a cable that monitors the throttle position. The 82 Cad that I did has the original 2004r that was behind the 350 Diesel. Got to be gental in 2nd gear or it slips the band. Got lots of torqe. Once you get in 3rd and od no problem. First gear is no problem.
Dan

[convert2diesel]

Dan:

How did you ever get a BOC type tranny to marry up to a 6.2? Lucky you didn't take out forth gear. I tried that combination but could never get the right adaptor plate.

The 400 equipped 6.2 had a vacuum regulator attached to the passenger side of the throttle arm. This should be sufficient to regulate the 350. Failing that, this would be a fairly simple control to fabricate.

Jbell:

Will try to scan it in tommorow and send the chart to you. By the way, if you think the DMax is dependant on computers, wait till you see what is attached to the VM Moterie that the Jeep will be getting. This engine has been very successful in Europe for a number of years and gets great mileage, but don't let anything happen to it. Has been known to create spontanious wallet combustion when repairs are needed. Will stick with the tried and true for now.

Bill

[catmandoo]

convert lots of them had the dual bolt pattern.

[convert2diesel]

Catmandoo:

Could be a regional thing. Up here in the great white north, all the 200s I have come across attached to the older 5.7s were the BOC style only. Only wished I had known then about the dual style. Would have saved me a bunch of time and energy.

Bill

[jbell]

spontaneous wallet consumption? Sounds worse than a 50% off sale that my wife attends.

Yea, tried and true, perkins 354T, 12valve 6BT, my 6AT, and a few old hercules that are around, and now my newest toy, my NA6.2 sub. I looked hard for a herc 3.7dt for my jeep, before I found my 6AT. Love my 6AT, wish cummins hadn't killed it, after they bought onan. (It's my mpg king)
My tacoma is over 310,000 and probably will be in need of a diesel repower in the next 100,000. (Always In pursuit of mpg, and the wonderful smell of a diesel....) Any tried and true for it? (other than the toy 3L?) Don't think a 6.2 would fit....

[84 Convert]

My $0.02 on fuel quality vs. economy...On my last job, I drove many miles in a '94 Dodge flatbed dually loaded with tools. I could get fuel here in western WA at the Pacific Pride stations and would get ~16mpg. But fuel at Pac. Pride in OR and I would get ~20mpg! only thing different was the fuel. I repeated this performance at least three times. Driving style was the same as I have a hereditary abnormality...my right leg and foot bones consist entirely of LEAD. Oh, yeah and OR driving invariably involved climbing one pass or another. Logging roads always a part of the mix.

Gregg

[G. Gearloose]

Spotted a old Buick GN yesterday , thought that would be a sweet ride with a 6.x..and 3" duals..

[Dan Wilson]

If i remeber right i did get an adapter from TCI Racing trans co. They have lots of adaptors. http://www.powerandperformancenews.com/store/merchant.mvc?Screen=PROD&Product_Code=230000&Category_Code=&Store_Code=TC
Good idea to use the 400 shifting parts with 350C. I believe I have seen dual pattern 350C's.
Dan

[convert2diesel]

Jbell:

Didn't get a chance to do your chart today but will work on it. As per the Tacoma, if that guy up north could shoe horn a 6.2 into a Vette, anything is possible.

84 Convert:

Fuel quality may not be the problem. Could it be that the station in Wasington was still pumping winter fuel? I find a 10% to 15% decrease in mileage using the 20% kerosine mix we use up here as winter diesel (#1). Also could it be a difference in altitude? Just guessing here.

G. Gearloose:

Having just survived fabricating a 3 inch single on the Roadmonster I can't even envision doing it twice on the same car :D . That also begs the question...To what benifit would dual 3 in be. I would think 2 1/2 would be more then enough. No to mention that most of the system you could buy off the shelf.

Dan:

Now that I am using the 6.2, my tranny options are more universal and I don't have to work around the problems normally associated with the 200R4.

MP:

Getting back to the topic at hand, I know I have just spent the last week advocating lowering the HP requirements as opposed to tweeking the engine but I will now digress.

Almost without exception, anyone I know that have either installed a puffer or purchased their truck with one on has said the same thing. Namely the mileage at normal speeds has been 2 to 5 MPG less then the equivalent free breather. After reading the other posts this seems to be a universal complaint.

Could it be that the combination of exhaust restriction and intake air restriction at low boost pressures are effecting the performance? Perhaps the following would work:

1. Install a seperate "Swanger Air" intake and filter directly into the manifold, bypassing the turbo, with a wieghted air door designed to close at anything over atmospheric pressure allowing the turbo to pressurise the sytem when needed.

2. Install a larger exhaust by-pass to reduce back pressure when turbo not required.

3. Manually switched vacuum source to the wastegate, allowing the driver to activate (or de-activate) the turbo.

Especially on the older 6.2s or the converted NA 6.5s this arrangement should return these engines to thier original selfs but would retain the turbo when it is really needed.

Just some thoughts

Bill

[G. Gearloose]

3" was just to peg the coolometer, plus Dr. Lee is a fan of the 3" with crossover,and appears to attribute a portion of his good performance to it.

I concur a tru dual 2.5" with crossover could be adequate strictly reguarding milage.

[More Power]

Personally, I think the light-load fuel economy for a TD is very close to that of N/A. If you need the extra power provided by a turbo, it would be worth the trade-off, in my opinion. However.....

The biggest problem with a turbocharger for a strictly fuel economy rig is the nut behind the wheel. Unless there's an individual out there with a lot more willpower than myself, a typical TD owner will accelerate harder, drive faster and use the power more often than when driving N/A. This hurts fuel economy.

Other drawbacks for a TD include cost and complication for an otherwise simple to maintain engine. But, after towing a 14' camp trailer with an N/A 6.2L for several years, I know how important a TD is when towing. Headwinds and hills are not a lot of fun for an N/A.

MP

[Stage1]

Again I am building/reconstucting a 84' Blazer and am interested in your thoughts on goal for engine RPMs at 65 MPH? Blazer will not be used for towing much, however, hills are part of the roads here. Review of comments has me thinking about the range of 1800 to 2200. Origionally thinking about 2200 before this thread started, is 1800 hard on the engine because of loads caused by going up hills, etc? How much fuel is saved by 1800 vs 2200?
I must also admit, enjoy putting the right foot down once in a while for that diesel fuel tank high.
thanks,
Les

[84 Convert]

In this case I seriously doubt winter fuel. The stations I was using are mostly used by semi-trucks, so fuel turnover is rapid. Also, this was happening in the middle of summer.

Gregg

[Salemone]

I have not seen any reference to the benefit of reduced pumping losses when using a turbo. The back pressure in front of the turbo is free. The back pressure after the turbo may be more of a
parasitic factor.

Is there any scientific proof that a properly
sized turbo will not increase your mileage by
reducing pumping losses and providing an oxygen
rich condition allowing complete burning of all the fuel in the chamber.

[Salemone]

MP,
The power plant I would pick for max fuel mileage
regardless of the vehicle would be:

6.2 - stock compression- GM wastegated turbo-
DB 2829 Injection Pump calibrated for 1983 C
engine. (can be turned down in a "CAR" vs "truck")

6.2= smallest displacement.
GM turbo= low end boost (reduces pumping losses)
DB 2928 IP= Less hp to run.

My $.02
Salemone

[More Power]

Salemone, Good choice! I would also add a gear drive timing set, balanced rotating assembly, and matched ports.

MP

[jbell]

Thanks Convert2Diesel

http://www.christ-our-savior.com/web/j%20power%20curve.JPG http://www.christ-our-savior.com/web/j%20specs.JPG http://www.christ-our-savior.com/web/c%20power%20curve.JPG http://www.christ-our-savior.com/web/c%20specs.JPG

[Ratau]

MP

Very interesting topic, what is your final conclusion?

Most off the replies suggested tall gears (3.08).

I get

[G. Gearloose]

There is a point of diminishing returns. Too low and your on the pedal too much under real world conditions.

with a 700r4, and if you hate dropping out of OD for modest grades..
3.08 is ok if your tires are 30-31".
33's perform better at 3.56-3.73
35's like 4.10's

I changed my K5 from 10b 30"/3.08 to 10.5" 35"/4.10s and got the similar corrected mileage, within a mpg; and I think it got better.

[Ratau]

G. Gearloose

I got most off the spares to install a turbo. At an altitude off 5500vt diesel engines need some kind of altitude compensation.

I plan to change to gears to 3.73 or 4.1.
I got 31

[convert2diesel]

Well I now have some initial mileage figures for the diesel Buick.

Just returned from a 2,500 mile trip from Ottawa to Georgia and back. Calculated in Canadian gallons they ranged from 27 MPG (#1 winter diesel through the hills of Pennsilvania) to 37 MPG on the flats through North and South Carolina (80% Bio-diesel, 20% #2 summer blend), with an overall trip average of 34MPG.

Using the cruise control we maintained a steady 70 MPH, holding the engine at a constant 1,950 RPMs. The weather was coolish (45 to 50) except in the Northern States when it dropped to 15 in New York.

I will now start to tweak the pump and timing, and maybe go for a higher flow injector to improve spray pattern. It is my hope that at 60 degrees and at highway speeds I can consistantly get 35 to 38 MPG. That should equate into about 21 to 25 MPG with the trailer out back.

Bill

[dieseldummy]

How does that relate into us gallons?

[G. Gearloose]

Originally posted by convert2diesel:
and maybe go for a higher flow injector to improve spray pattern.
This first sounds counter-intuitive to me...could you elaborate?

[moondoggie]

Good Day!

Dieseldummy asked,

[convert2diesel]

Gearloose:

It may sound strange but oddly enough, improving the flow, pressure and subsequently the spray pattern, means a more efficient burn. These engines were designed as a total compromise so any thing you do to improve the burn characteristics can only help to improve the fuel economy.

Moondoggie:

Maybe it would be easier to first convert to liters. Your girlie gallons :D only contain 3.8 liters while our macho gallons take up 4.546 liters.

Either way the 80% rule is close enough.

Bill

[More Power]

Ratau,

In a typical pickup or Suburban, I would gear the vehicle to produce 1800 rpm at 65-mph for best fuel economy. That usually works out to be 3.42 gears, .69 OD (700R4) and something like 30" tall tires. A lower/lighter/less drag vehicle may change the scenario somewhat, as would more weight, drag or higher speeds. If you're after economy, stay at or below 65.

MP

[jdmetcalf57]

I recently returned from FL and did some testing on the way. My truck is a 99 k3500 and I hooked up gages for boost pressure and back pressure. I normally pull a 4K hilo type camper. My mileage on this trip run about 14.5 to 15. On one tank I bumped the boost up about 3-4 psi to see what effect it had. Normally it runs about 5psi cruising at about 70mph. I actually lost about .5-1 mpg. What I found was that the back pressure rises significantly more than the boost. At 2100 rpm every lb of back pressure robs about 1 hp just from pumping losses. (power = Volumetric flow rate * pressure)have to use the right units

I think there is some significant gains to be made by engine mods. My truck runs about 15-16 mm^3/ignition when in neutral and 2100 rpm. Try this if you have an electronic fuel injection system and can monitor the fuel rate. If you figure 63mm^3/ignintion gives 195 hp net then 63-16 gives this horspower. Then 16/(63-16)*195 gives how much horsepower it takes just to turn the engine over. This is 66 hp. I'm sure the fuel vs hp curve is not totally linear but it at least gives us an idea.

I can also back figure the mileage empty of 20mpg at 2100 rpm gives 27mm/ignition which assuming 16 is taken to turn the engine over leaves 45 hp to drive the truck down the road at 70mph. I have done some test where I find the speed after coasting 1/4 mile on a flat road and windless day starting at 75mph. From this I can calculate an estimate of 50 hp to drive the truck down the road. This is good correlation for the crude methods I have at my disposal. Pulling my camper I have hp estimates in the 80-90 hp range.

Anyway from these numbers it looks like there are major gains that could be made in the engine at least equal to that which can be gained by aerodynamics.

I am anxious to see what improvement I have made with summer fuel. Last year going to FL I only got 12.5-13 mpg. Since then I have got rid of the duals and put a manual trans in. Considering when I got the truck I got 10.5-11.5 mpg I have come a long way.

[Ratau]

Jdmetcalf57

Would it possible for you to post the exhaust pressures you get at different boost levels, what turbo you use and the compressor housing A/R is?

This info could add to Stray Cat

[jdmetcalf57]

Won't be able to do it for some time. When I got back from FL I discovered antifreeze in my oil. The truck is at the dealer now and I should get new engine on warranty. I've heard rumors that the engines take a long time to get though.

[john8662]

I'm bumping this up to and keeping this post at the top for awhile now because of the increased need for better fuel economy. With fuel here at 2.36/gal I'm getting geared up for better economy and concentrating less on more rear wheel HP/TQ. Great ideas here!

[jbell]

Yea, this is a good topic.

Here's cummins take on the subject. Good info and puts things in perspective. What applies to tractor/trailers, applies to suburbans, and pickups, just on a smaller scale.
http://www.cummins.com/na/pdf/en/products/truck/MPG_Secrets_Whitepape.pdf

IMHO A front air dam, and a partial tonneau should be something we all try. I've had good success with both my toyota and my 6.2 burb.

http://www.freepatentsonline.com/4573730.html

[jbell]

OK, I've got some mpg numbers from my 'redneck engineering' experiment on my toyota tacoma.
It's a 95.5 model 4x4 sr5, on BFG AT 32x11.50r15's with the stock 3.4 v6, manual 5 speed and 4.10 gears.
It currently has a little over 320,000 miles. It NEVER varies on fuel mileage, I drive 75mph average on a 90mile round trip commute daily.

For the last 9 years I have ALWAYS gotten 18.5 mpg. (plus or minus 0.1mpg when commuting)

I have averaged the following over multiple tanks, so this is for real, it's not a fluke.

Here goes the modifications.

1st. 6" front air dam, made out of 3/4 plywood, blunt, square, definately NOT aerodynamic.
20.5 mpg
2nd I added a 1/2 tonneau on the rear half of the box (like in gm's patent)
20.5 mpg (Hmm.....)
3rd, I put back in my low profile aluminum tool box, and left in the rear 1/2 tonneau. (1 foot open area between tool box and tonneau.)
21.6 mpg. (I also noticed the wind noise is ALOT less inside the cab)

total improvement 17%.

Next is to make an actual 'real' aerodynamic front air dam, as the air dam appears to make the most difference.

Goes to show that aero is the key to good mpg.

[blazer84]

a cabbie was whining to me the otherday, about the cost of gas in the Crown Vic he rents. Why couldn't (wouldn't?) GM make taxi specials, w/cheap (NA -even cheaper) 6.5 in Caprice chassis? All the tooling is paid for. Seems like a perfect engine/car combo . . . for a cab for sure :cool:

[ 05-16-2005, 11:59 AM: Message edited by: blazer84 ]

[aloharovers]

Originally posted by jbell:
It NEVER varies on fuel mileage, I drive 75mph average on a 90mile round trip commute daily. Not to be a wiseass, but I bet if you dropped it down to 55mph you would pick up another 2mpg.

Pete

[K10ANDY]

i say more than 2 ! the 4x4 rags did a mpg article and if everyyone slowed to 55 it would be iirc 25% increase .

[jbell]

yea yea yea..... I know.

The old racing saying "Speed costs, how fast do you want to go..." applies.

However, in my case, I like to think of "Time is money" And I hate to waste either.... so 75+ it is..

I've run several tanks full through, and still getting 21.5 average. Not bad for a vehicle that has seen over 1000 fill ups, and has as window sticker epa rating of 17-19. (When was the last time anyone else could exceed the epa mileage rating of a vehicle running over 75???)

[James68352]

I've been following this thread and like what I have seen so far. I had the chance to do some checking this past weekend on a camping trip.

the facts:
total trip mileage : 93.5
diesel used : 8.773 gal
MPG : 10.6577
head wind for about 30 miles : 10 MPH
cross wind for the rest of the trip : 10 MPH
average speed : 55
truck used : 82 k1500 4x4, 6.2C with a Jcode intake, NP833a tranny, NP208 transfer case, 10 bolt 3.08 axles, 31x9.50x15 tires, stock 2 1/4" exhaust, stock everything except the J code intake,
trailer : 2005 Keystone Outback 29fbhs, 31' fifth wheel, weight of 9500 lbs.

I know that the trailer is well beyond GM's GCVWR for this setup but it is what I can afford at the moment.

Jim

[G. Gearloose]

Check out the graph , James.
The fuel flow at 1600rpm is the same as 2800rpm, but the power almost doubles, and that means less foot on the pedal to make equivelent power. You could change gears with 3.73or 4.10 3/4 ton axles (they bolt right up), or go with a common mc465 tranny, with 1:1 top gear.

appendum-
Additionally, when you cruise on the high rpm side of the torque peak and you hit a hill, avail torque increases as you slow, instead of dropping away, this helps you maintain speed.

[ 06-29-2005, 03:27 AM: Message edited by: G. Gearloose ]

[Tatraplan]

I get an average of 19.6 mpg with a 150hp 6.2
J-engine, 700R4, 4.10 rear & 9.50 R16.5-tires.

Best so far is 20.3, but today I discovered a
small fuel leak from one of the return hoses
from the injectors. Replacing it might be an
easy way to increase mpg a little.

/Robert

[More Power]

Got a screaming deal on a new project vehicle over the weekend. Will be trailering it home today. :D

This time next year, we should have most of the answers concerning what works for a vehicle (El pickup) to deliver max fuel economy using a 6.2/6.5.

I'll post a pic or two and an outline for the project before long. smile.gif

Jim

[moondoggie]

Good Day!

Thanks for making my day - can't wait to read EVERYTHING about this.

Blessings!

[panchosteam]

Hi guys, i now have a 1986 silverado k 20 silverado suburban automatic transmision and 3.73 gears according to the glob box, took the family on a trip from Long Beach Ca. to perris, then from Perris to Sun City, back to perris then from there to the lake, according to the instrument panel it was 188 miles round trip ( just installed 235/85/16 DUNLOP ROAD ROVER A/T TIRES on saturday) filled up diesel tank before left, filled again on come back and the results are 16.22 gallons round trip for $2.89 gallon, is this any good? like 11.59 miles to a gallon?
speed was between 70/75 most of the time. 1986 6.2 SILVERADO K20 SUBURBAN AUTOMATIC TRANSMISION AND 3.73 GEARS?

[GregCrabb]

quote:Originally posted by jbell:
It NEVER varies on fuel mileage, I drive 75mph average on a 90mile round trip commute daily.

Not to be a wiseass, but I bet if you dropped it down to 55mph you would pick up another 2mpg.

Pete

It's true.....in my TDI beetle, I dropped just 5mph from 75 to 70...went from avg. 47mpg back up to 50+mpg
Haven't checked my 6.2 lately...may drive him this week.

[moondoggie]

Good Day!

panchosteam: One tank of fuel tells you just about nothing about mpg. I don't say this to create any offense, but most folks are unaware that it takes a LOT more data than one tank to know anything about your mpg. ;) If you want to know why I think this way, you might want to look at my gasohol mpg (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005648#000004) (click in colored text) post.

The 84 Sub I used to own (3.73 gears, 700R4) would reliably return > 20 mpg on the highway, but I always drive the posted, so I seldom drove even 65 mph. mpg on the 84 Sub, & the 82 pickup in my profile, seems to drop DRAMATICALLY over 60 or 65 mph. :eek:

Blessings!

[panchosteam]

Thank you guys, MOONDOGGIE: i'm just trying to figure this new to me 1986 6.2 suburban and try to figure the MPG

[Craig M]

Hey Panchosteam, you are in my neck of the woods. That does not sound like to good a mileage for the Suburban. Our 82 has the same gears and 700R4 automatic. Does yours have the TH400 or 700R4? Around town we get around 18 mpg and on trips a little over 20 mpg. We do not go much over 65 mph with it. 75 mph and TH400 would both hurt the mpg, but should still do a little better than 11/12 mpg.

[panchosteam]

Thank you CRAIG M, i found some leaks on this truck so i'm going to have to work them out and go from there,could i do better with 245/85/16 ? or will it be worse? about the trans. i was trying to find out which one i have but i could'nt see the info on it, to greasy , i think i saw something like turbo... i do not remember i will have to check again, any way i'll be checking for mor leaks tomorrow after work
i also found a bad motor mount on the passenger side so after i change it maybe i can see ifthe lift pump leaks. I liked the way my 1984 sierra pick up used to ride with the 6.5 td engine on it so that's why i went ahead and got this other diesel,one thing for sure is that it doesn't ride like my pick up, this suburban been a 4x4 is not comfortable as i expected it to be when i get better mileage on the diesel i'll be happy!

[Truckie117]

Hey guys
Im new at this I have my 99 chev sub 6.5 about 3yrs and have had the pmd changed twice. when I first got the truck it did about 20mpg at 60 since the pump was changed cant do any better than 17mpg at 55 - 60 what could change the milage?
Thanks the new guy

[moondoggie]

Good Day!

I'd bet timing. You might want to get it hooked up to a Tech II or such & find out what the TDC offset is presently. I don't know what TDC offset will produce the best mpg. In fact, I'm not sure anyone does. The good news is that More Power has already purchased his next project truck, which is a 6.5 & will be set up to find out such things. :D

Blessings!

[FrankJack]

You know, I have spent a few minutes digesting the postings to this mileage issue. I got my engineering degree in electronics/electrical but the facts still remain that increased pumping loses of a turbo will decrease efficency provided adequite air/fuel ratios are maintained. This being said, the additional back pressure of a turbo can produce loses in efficiency in the mid-range area of a diesel engine. If we all agree that the "optimum" range is 1700 to 2100 RPM for the 6.2 then we realize that a trubo will probably not add but take away from efficiency. I.E. lose mileage. At higer RPM's this will not be true and at lower RPM's, there will be no effective restriction. The key here is to have a turbo that will spool up with boost of 1+ PSI after the 2000 RPM and produce about 6-8 PSI at about 2800 RPM. Makes pulling a hill with a load efficient but does not add to the pumping loses at 1800 RPM crusing. All said, the 6.2 is a well balance engine. With a Banks it is even better. Flying a GMC (Brick in the wind) truck is not the most efficient but is an albeit usefull and confortable means of transportation. And anyone that is getting about 20mpg pushing this brick down the road is not doing badly.
If you want gains in mileage, reduce the air friction, rolling friction and increase gearing to the 2.88-3.08 final drive ratios. Back off the boost at mid range, and save the power circuit for pulling at full throttle only.

[Lightyear]

This is all fascinating, especially to a kindergarten-level diesel enthusiast like me. On my last trip Atlanta to Gulfport for weekend ANG duty, I got an average of just under 19MPG calculated over three fuel stops (not knowing availability of #2 on the Gulf coast). That's in my '88 6.2 Banks 4wd with a non-functioning TCC. Kept it at 65 or below as much as possible. The trip took a little longer, but my wallet wasn't as light afterwards.
I really appreciate this forum; it's a great way to learn about these neat old beasts.

Buzz

[mhagie]

Just put ol blue away for the winter, last two tanks average 19 mpg @65 mph back and forth to work 65 mile rt.
won't complain with this mileage, think it would hit 20 w/out the town portion.
Now if I can find my STA-BIL I'll be set.
Merle

[perch]

Hi,Just my experiance,1989,6.2, chevy 4 by 4,2500,running boards,3.73,262000 miles,

temp.20, At 55 tail gate open 22mpg
temp.70 at 55 tail gate open 24mpg best ever
at 65+ 19.3 tail gate closed.
short trips,farming,haul,pull trailer,my normal 16.3mpg

Merry Christmas
Butch

[More Power]

Well, a logistical challenge has been overcome, and the 6.5L El Camino project will begin soon.

As soon as I acquire a couple decent images (of someone elses Camino) to use as a lead-in for the introduction, I'll post a new article that outlines the project, and hits the highlights for maximizing fuel economy.

For now, you can visit the following link to see what a 1972 Chevrolet El Camino looks like.

Link (http://www.elcaminoclassics.com/image/skidmore/skidmore-01.jpg)

Jim

[AndyL]

Jim, I am plannin' on giving you a run for your money in the Olds! At least on mileage :D

[More Power]

The Max fuel economy project (http://www.thedieselpage.com/features/elcamino.htm) has begun! While this will be a max mpg project using a mechanically injected non-turbo (to begin with) 6.5L diesel, much of what will be discussed can be directly applied to all 6.2/6.5 diesel equipped vehicles (including some aspects of a Duramax equipped truck as well). We may even be using some 6.2 specific components…

Things like engine rpm, vehicle weight & drag, and driving strategies for max fuel economy will apply to just about any light diesel. Our vehicle choice will allow us to explore what effect weight and drag have on fuel efficiency.

I think you'll be surprised at what components are available for all 6.2/6.5 diesels (EFI and MFI) that were designed to improve fuel economy, and we'll be discussing them in future Project MPG updates. Some components you may already know about, but there are a few you probably don't… At least not yet!

Jim

[HANK1948]

MP,
What ever happened to the 6.5 powered s-10 blazer you talked about in Florida? Ive always wanted to do something like that because Iam sure it could get 30+ MPG

[More Power]

It was one of those phone calls - like many I receive - from a member who told me what he had done. I asked that he send some images and discussion to let more people know about his project. That's where it is... We'll wait & see...

I'd like to see it here, cuz it adds to what we're doing with fuel economy.

Jim

[rjwest]

My early 82 ( delivered in Nov81 ) 3/4 2w
4 sp std tran w OD, ( weighed 5500 lbs )

24 MPG, always, drove truck to 230K miles
( 1 rebuilt pump ) sold it and it ran more miles,

I would note that the fuel back than was
heavy,yellowish, and not as much foam...
Ah, Progress... ( house oil ran good also.)

[More Power]

6.2L/6.5L Fuel Economy (http://www.thedieselpage.com/features/65fueleconomy.htm)
Cylinder Heads & Ricardo Comet
Part II

The 6.2L diesel engine was introduced during a time when the world energy market sent fuel prices skyrocketing. While it may surprise you, gas & diesel pump prices during the early 1980's were actually higher than they are now - when adjusted for inflation. GM's 6.2L diesel was designed and developed for tight fuel supplies and high pump prices, and we may need to revisit the 6.2/6.5 to help provide a solution to the high fuel costs we're seeing now. The early light-duty 6.2L diesel powered trucks would consistently deliver 22-24 mpg when driven conservatively, while the later light-duty 6.5L turbodiesels produced 5 or more miles per gallon less. Why is that? The answer to that question is what we're investigating this time.

[DanSSj4]

I have a '92 GMC Vandura 3500 work van I go as fast as 75 mph Max(Rarely) never tow with it, have 2 3500 6.5 TD 93 & 97 It currently runs a wore out 350 in. Gas Engine I want to convert to diesel for equal or a little bit more torque but better gas effieiency what would work best for suck a heavy, large, non airodynamic brick.

Also on another subject the housing for my Differential is damaged where the driveshaft comes in and there is extra play it bangs sometimes. I plan on just replacing the whole rear end with a newer lower milage one What readend would give me the best Fuel Economy, power is unimportant because I drive the van REALLY Slow

[djw32]

More Power,
The 6.2/6.5 article is great! Please keep the articles coming.

[Overdrive440]

I have just stumbled across this forum. I am trying to get away from the uncomfortable and noisy ride that is a small 4 cylinder econo-car, but I want to keep the high fuel economy (or close to it). I can't wait to read more on the El Camino project. :)

[woodywp]

I owned a 1982 K1500 SWB 6.2 with a manual 4 speed with OD and 3.42 gears. This truck broke 30 mpg on several ocassions driving at 58-60 mph and doing my very best to be smooth on the pedal. I would build a little speed down hill at let it fall off some on the next hill. This sounds to good to be true now but I always fill up to where I can touch the fuel in the neck of the filler. Having since owned 2 other 6.5 turbos a 1994 K3500 LWB 5 speed manual 4.10 18.5 mpg and 1995 2500 Suburban 4 speed auto 3.73's 18-20 mpg I would say 6.2 NA without a doubt. I would really like to have my old truck back now with fuel prices what they are.

[Chevrolet4x4s]

6.5 Turbo Diesel
Here is my plan. Let me know what ya'll think.
1973-1974 Chevrolet short stepside
Tonneau cover.
Front air dam.
Rear roll pan.
Lowered around 4/5.
Ton sway bars.
Poly bushings.
Aligned real good.
T-56 6 speed.
Synthetic lube in the rear end.
Small mirrors.
Custom built headers for the turbos(plural:D).
GM-8 turbos. may go with one GM-8 and a little turbo off of a daytona or caravan.(which should deliver the best economy).
3 inch downpipes.
3 inch or 3.5 inch NASCAR boom tubes with x pipe daul exit right under the steps no mufflers for as long as I can get away with it.
Daul front mount intercoolers.
Possibly a cowl hood to let air out of the engine compartment better.
Free flowing air intake to the turbos.
Ported intake or maybe make custom Ram Logs similar to this(which should deliver the best economy).http://banksdiesel.com/Dmax-Gallery-images/intake/1_original_sketch.jpg
May go with rear disc brakes.
May do a partial bellypan.
Daul electric fans.
Polish up the exhaust ports a little.
40ish psi in the tires
No A/C (I hate ac in a vehicle..gives me headaches:rolleyes:)
And a slick shiney black paint job:cool:.

Here is the 73-74 grille after I redid it
http://www.hotrodders.com/forum/attachment.php?attachmentid=24798

and what I started with http://www.hotrodders.com/forum/attachment.php?attachmentid=24799

Heres the step by step process
http://www.hotrodders.com/forum/repairing-rejuvenating-restoring-plastic-grille-125972.html

I am hoping for 30mpg plus while crusing with a light foot. Do you think it is possible? Any thoughts or suggestions?
Thanks
Shane

[allformike]

I Have Been Getting 19 City- That's Between 35-40 Mph. And About 21 0r 22 At About 50 -55 Mph. Hows That Sound For A 4x4. Puts Gassers To Shame. Yay 6.2

[allformike]

i thought i was going crazy, but indeed i am not. for the last 3 tanks i have been getting 25 mpg. i run the winter bottle of power source and have put 30'' mickey thompson baja claw radials on, with a th400 and 3.73's:D:D

[trbankii]

and have put 30'' mickey thompson baja claw radials on, with a th400 and 3.73's:D:D

Have you compensated for the tire size and gears in the mileage?

[allformike]

i put them on to replace the 245 65r16 tires i had on it. i put the larger tires on to in tern slightly reduce the ring and pinion gear. what i mean is that with a bigger tire it is spinning the gears slower so the engine is reving lower, therefore giving a slight increase in mileage. form doing this i picked up a extra 2 or 3 mpg. i also drive it very easy and have a fresh IP rebuilt a good flowing 4'' exhaust, the intake mod i posted and the winter POWER SERVICE WHITE BOTTLE.

[veager]

88 crewcab 3/4 ton 6.2 diesel(newer heavy casting) turbo charged(some rotomaster I found on swap meet),ported heads( everything made in the backyard except 6.5 exhaust manifold) coupled to nv4500 5 speed through 3.42 gears.
28 to 32 mpg @65 ish 21 to 22 @85mph.
Hate to say it but my duramax doesn't even come close.
Just punched the block to 6.5, had piston top cracking with 6.2 pistons.
6.5 pistons have more meat in the top area(mahle pistons).
Not sure what this will do for mileage but hope it will be just as good.

[dieselcj8]

so far im getting 34 mpg in my jeep, 6.2 n/a, 2600 lbs, 33" tires, th400, 3.31 gears

[Edahall]

It was very interesting following this thread. I have a 1982 Suburban with the original 6.2 diesel and Scenario #2 is what this rig is set up for. Last year, I took a road trip around the US and added 15k miles on the odometer. Since fuel was much more expensive than it is now, I kept my speed 60 mph (1600 rpm) since I was not in a hurry and this is where I could pull in the best mileage. I consistently got 28 mpg and got at high as 32 mpg on several tanks.
Here's my setup:
2 wheel drive
3.08 gears
700R4 transmission from 1989 truck
30”x9.50 tires
Ported and polished heads – 1983 heads
Intake manifold runners matched to heads and casting smoothed out
Exhaust Headers
Dual 2-1/2” exhaust with H-pipe
Timing gear
Injection pump turned up ¼ turn

I also tow a 26 ft. Airstream which weights around 6000 lbs. I tow in 3rd gear and 2nd gear on the hills. I can manually lock the torque converter to keep the temperatures down on long grades. I get 16 mpg with this setup.

Some things that I could do improve economy:
Super Tune engine using glow plugs.
http://www.ford-trucks.com/forums/593483-using-glow-plugs-to-super-tune-the-engine.html

Hydrogen Generator
http://pesn.com/2007/01/08/9500445_Bob_Boyce_Electrolyzer_Plans/

Aerodynamic mods such as front air dam and rear fender skirts

[Dieselmania]

Moondoggie:

Yes you are correct. There has been lots done to make these trannies more durable, and to allow them to standup to some incredible punishment. For an overdrive tranny that doesn't need electronic assistance to operate (with the possible exception of the lock-up) it would fill the bill for most use.

What I was trying to accomplish was incorporating the concept of "gear splitting". In an attempt to use this engine in it's naturally aspirated state to tow more then a light boat trailer.

It is very important to keep this engine within a very small torgue band of 1,600 to 2,200 RPMs. While this is possible with a 4 speed (8 speeds with aux tranny), the resultant double overdrive is way too low at highway speeds. If I go to an underdrive, the first gear under could be used to pull stumps out of the field and generally not useful.

That sent me looking for a 3 speed tranny, with a lock-up torgue convertor, that could handle the out-put of the 6.2, and then add the overdrive aux tranny.

My local guy said he could build up any tranny I want, but I was looking for anyone who had experience with the 350"C" behind our engines.

MP:

While I doubt the numbers the Corvette guy is getting, it illustrates what I was trying to get at. Namely lower the HP requirements and these engines do quite well in the economy department.

Would be very interesting to see one of these with 7,500 lbs of Airstream hung on the back :eek: . With 4 1/2 in of clearance I wonder if he could even get it into the campsite without leaving his oilpan at home.

Dan:

Man after my own. This is number four for me. Got tired trying to get any power out of the 5.7s though they did get great mileage, so am now doing the 6.2/6.5. This is the best one yet (knock on wood). Short of some logistical problems that are easily solved, it was reasonably painless. Now on to a 93 Fleetwood :D .

A belated Merry Christmas to all

Bill

My dad had an '82 caprice with a 5.7 diesel, 350c tranny with a lockup torque converter, and 3.08:1 rear axle ratio ...it got 35mpg running 65-70 on I-40 going from Jackson Tn to Cookeville Tn and back. A few months later, the 5.7 stripped the head bolt threads out of the block ( blowing the head gasket ) and the car got parked. If I hadn't moved to Oklahoma, I was going to replace the 5.7 with a 6.2

[john8662]

Hmm, I may join in on trying to get some more economy out of a 6.2L.

I picked up another 1982 Short Bed truck, but I want to just drive this one with the 6.2L engine with the hope of better economy.

My other 1982 SWB truck got 25 at 70mph pretty easily when it was a 6.2, pretty stock engine and truck. My 86 LWB got 24 at 65, and 22 at 70, so I liked the 25 the lighter truck got.

This new one is lowered almost 6", and I figure that would help the drag bit, plus I'm going to help the engine run a little better to increase it's efficientcy (exhaust, air, stuff). My hope is 29-30mpg at 65mph eventually, or around 27 at 70mph.

As soon as I get the specifics on the truck hammered out, testing will occur. Someone removed the TH700 and installed a TH350, since i have the engine and trans removed from the truck at the current I will be going back with a good TH700 I have, and then will identify what the gears are in the rear differential (hoping for 3.08), and I have a 2.73 to try as well.

J

[Edahall]

Hmm, I may join in on trying to get some more economy out of a 6.2L.

I picked up another 1982 Short Bed truck, but I want to just drive this one with the 6.2L engine with the hope of better economy.

My other 1982 SWB truck got 25 at 70mph pretty easily when it was a 6.2, pretty stock engine and truck. My 86 LWB got 24 at 65, and 22 at 70, so I liked the 25 the lighter truck got.

This new one is lowered almost 6", and I figure that would help the drag bit, plus I'm going to help the engine run a little better to increase it's efficientcy (exhaust, air, stuff). My hope is 29-30mpg at 65mph eventually, or around 27 at 70mph.

As soon as I get the specifics on the truck hammered out, testing will occur. Someone removed the TH700 and installed a TH350, since i have the engine and trans removed from the truck at the current I will be going back with a good TH700 I have, and then will identify what the gears are in the rear differential (hoping for 3.08), and I have a 2.73 to try as well.

J

Having a 3.08 rear differential is probably about at tall as you want to go with an overdrive transmission unless you are planning use very small diameter tires. My 82 Suburban has 3.08 gears and a TH700 and it is pretty gutless at 60 mph in overdrive. It has more performance at speeds over 65 mph but fuel economy decreases due to wind drag.

[abec]

my old 90 gm diesel has a good set its slow but i can get up to 30 mpg on a good highway run it has a 99 6.5 n/a turbo 400 with 4.10 gears in the rear end i just set the cruise at 60 and let little basterd go :cool:

[pologuy14]

so i just came back to the 6.2 world.
my suburban had a 6.2 mated to a th400 & 4.11s. it hit 17-19 mpg on long freeway drives.
i just bought a blazer/jimmy w/ the 6.2 mated to a 700r4 (not sure gears). havent done a full calculation but im getting close to 23-25mpg. this thing is totaly freeway friendly minus getting up to speed to merge onto the freeway.

& im just curious has anyone over heated one of these 6.2s(w/ a working cooling system)? i could not make either of them hit 200 degrees unless up a steep grade w/ my foot pinned

[jMedia]

Hey everyone new here, thought I'd post in this because it's basically what I'm gonna ask.

I have a 1988 Grand Wagoneer, currently with 3.31 gears (could change that)
lookin at a 2-4" lift with 32s
probably all onroad driving (never been offroading)
And I am not a heavy footed driver, though some power isn't the worst thing in the world :D

I was curious what everyone thought would be the best engine choice of the 4 for me?

[Edahall]

Hey everyone new here, thought I'd post in this because it's basically what I'm gonna ask.

I have a 1988 Grand Wagoneer, currently with 3.31 gears (could change that)
lookin at a 2-4" lift with 32s
probably all onroad driving (never been offroading)
And I am not a heavy footed driver, though some power isn't the worst thing in the world :D

I was curious what everyone thought would be the best engine choice of the 4 for me?

Either a GM 6.2 or Cummins 3.9 4BT. Do you have overdrive? The 6.2 likes to cruise at 1800 rpms and Cummins is a bit lower like 1500-1700 rpms. The 4BT would likely yield better fuel economy. However, a 6.2 that is set up with fuel economy in mind can yield close to 30 mpg.

[jMedia]

Unfortunately because of CA dmv I cannot do a Cummins swap.
But 30mpg?? I have heard so much less from others. How would you set that up?
I am in search of a whole knew drive train so I will be picking up some sort of OD transmission


Either a GM 6.2 or Cummins 3.9 4BT. Do you have overdrive? The 6.2 likes to cruise at 1800 rpms and Cummins is a bit lower like 1500-1700 rpms. The 4BT would likely yield better fuel economy. However, a 6.2 that is set up with fuel economy in mind can yield close to 30 mpg.

[Edahall]

Unfortunately because of CA dmv I cannot do a Cummins swap.
But 30mpg?? I have heard so much less from others. How would you set that up?
I am in search of a whole knew drive train so I will be picking up some sort of OD transmission


Here’s what I did to get 30 mpg (US) on my 82 Suburban.

1. I used 1982 heads with small pre-combustion chambers and large valves. These heads get the best gas mileage but suffered from cracking. Of course mine had cracks in between every valve seat so I installed liners between each valve seat.
2. Ported / polished the heads
3. Stan’s Headers – Made a big difference in power since stock power was 130 hp
4. Free flowing exhaust – Dual 2-1/2” with H-pipe and Thrush tube mufflers.
5. DSG Timing Gear
6. Ported / polished J code intake manifold
7. 700R4 automatic with overdrive
8. 3.08 rear end
9. Tall & skinny tires – 30x9.50 with 50 psi of pressure

And of course, the most important, an easy foot. To achieve 30 mpg, I have to keep it under 60 mph. Over that, it drops off rapidly with the square front end on the Suburban. For example at 75, it’ll drop down to about 23 mpg. The 75 mph gas mileage can be increased considerably with aero mods but I rarely drive that speed so I have not done any aero mods on my Suburban.

>> Unfortunately because of CA dmv I cannot do a Cummins swap.
I don’t believe the 88 Jeep Grand Wagoneer was ever offered with a diesel in the U.S. So technically, CA DMV won’t allow installing any diesel. However, if you push the right buttons, I believe you can get it through even with a Cummins. PM me if you’re serious about doing this swap and I’ll tell you how.

[jMedia]

Nice setup, I will be taking all of those into consideration once I get mine going. Some users on the other diesel forum are making me feel like I can't get good mileage without doing a 4bt with the specs I'm looking at of 3-4" lift and 32s.

I'm thinking of a turbo, which kind would be better for an mpg application. I've heard that they can increase or decrease mpg, depending. I know that they can back up exhaust a bit, decreasing mpg. I have been talking to another user tho who added hummer exhaust manifolds and said they breathe way better

[Edahall]

Nice setup, I will be taking all of those into consideration once I get mine going. Some users on the other diesel forum are making me feel like I can't get good mileage without doing a 4bt with the specs I'm looking at of 3-4" lift and 32s.

I'm thinking of a turbo, which kind would be better for an mpg application. I've heard that they can increase or decrease mpg, depending. I know that they can back up exhaust a bit, decreasing mpg. I have been talking to another user tho who added hummer exhaust manifolds and said they breathe way better

The lift and wide tires is counterproductive towards good fuel economy but low 20's with that set up should be achievable. With 32's, 3.08's would be too tall so 3.42's would probably be more appropriate. If the hummer exhaust manifolds fit in your Jeep, that might be the way to go. A good exhaust/headers will get you about 70-80% of the power of a Banks Turbo with a lot less complication. Add some head work and you can get very close to the power levels of having a turbo. Turbo's usually usually don't get as good fuel economy with solo driving. However, they seem to add efficiency under high work loads.

[jMedia]

I guess I should clarify more when I tell people I want 32s. I dont want 32" SWAMPERS haha I would like a regular tire. Havent researched them that much yet but not looking for a crazy offroad wide tire. Too much rolling resistance


The lift and wide tires is counterproductive towards good fuel economy but low 20's with that set up should be achievable. With 32's, 3.08's would be too tall so 3.42's would probably be more appropriate. If the hummer exhaust manifolds fit in your Jeep, that might be the way to go. A good exhaust/headers will get you about 70-80% of the power of a Banks Turbo with a lot less complication. Add some head work and you can get very close to the power levels of having a turbo. Turbo's usually usually don't get as good fuel economy with solo driving. However, they seem to add efficiency under high work loads.

[npauli]

Wow!

I thought I was doing good in my Duramax, but some of you guys have sure got me beat.

I've gotten a whole bunch of tanks around 25 mpg, and have flirted with 30 mpg on a couple trips, but I really gotta watch how I drive to get that.

Sounds like the right 6.2 in the right truck with the right gearing can beat that without even trying.

[millwrightjesse]

Im getting 25.3 MPG in my suburban

[T-1000]

Hey guys I have a question. I found a short bed 1985 two wheel drive. The body is rust free with the standard oxidization on the paint causing fading. The truck is a second owner with 155k on it. The tranny is a factory rebuild with 30K on it. The truck runs but I have not driven it yet. Someone told me the 2 wheel drive short beds with the 6.2 were rare. Always been a gas man so I need some info. from the pros. I can get it for $1000.00 dollars. This seems good to me, what do you think? How much is it worth and are these good motors. What should I look out for? Any insight would be helpful.

[Edahall]

Hey guys I have a question. I found a short bed 1985 two wheel drive. The body is rust free with the standard oxidization on the paint causing fading. The truck is a second owner with 155k on it. The tranny is a factory rebuild with 30K on it. The truck runs but I have not driven it yet. Someone told me the 2 wheel drive short beds with the 6.2 were rare. Always been a gas man so I need some info. from the pros. I can get it for $1000.00 dollars. This seems good to me, what do you think? How much is it worth and are these good motors. What should I look out for? Any insight would be helpful.

If it doesn't have rust and the body is in good condition, this is a excellent buy even if it doesn't run. The 6.2 diesel motor is excellent for what it was designed for. It was designed as a light weight diesel engine to provide excellent fuel economy. In 1982, the engine put out 130 hp and with the right setup, would return fuel economy readings of mid to upper 20's. And with the stock power output, it was reliable as well. However, trying to get more power out of the unit often is asking for trouble. At that point, the Cummins 6BT is probably better suited for making lots or power and still being reliable.

[T-1000]

Thanks for the info. Going to drive it this week. I think $1000 is pretty good from what I have heard.

[jMedia]

Great info Edahall, I tried to PM you but I did not see the option to in this forum. If you could email me or something that'd be great! surfphotosd at gmail dot com.

Thanks again!


Here’s what I did to get 30 mpg (US) on my 82 Suburban.

1. I used 1982 heads with small pre-combustion chambers and large valves. These heads get the best gas mileage but suffered from cracking. Of course mine had cracks in between every valve seat so I installed liners between each valve seat.
2. Ported / polished the heads
3. Stan’s Headers – Made a big difference in power since stock power was 130 hp
4. Free flowing exhaust – Dual 2-1/2” with H-pipe and Thrush tube mufflers.
5. DSG Timing Gear
6. Ported / polished J code intake manifold
7. 700R4 automatic with overdrive
8. 3.08 rear end
9. Tall & skinny tires – 30x9.50 with 50 psi of pressure

And of course, the most important, an easy foot. To achieve 30 mpg, I have to keep it under 60 mph. Over that, it drops off rapidly with the square front end on the Suburban. For example at 75, it’ll drop down to about 23 mpg. The 75 mph gas mileage can be increased considerably with aero mods but I rarely drive that speed so I have not done any aero mods on my Suburban.

>> Unfortunately because of CA dmv I cannot do a Cummins swap.
I don’t believe the 88 Jeep Grand Wagoneer was ever offered with a diesel in the U.S. So technically, CA DMV won’t allow installing any diesel. However, if you push the right buttons, I believe you can get it through even with a Cummins. PM me if you’re serious about doing this swap and I’ll tell you how.

[tomtaylor]

My diesel page books are packed away right now and I trying to remember when GM changed the head/precup design I have an 86, are they different from the 82 heads by much???

[Vin82k3500]

Great info Edahall, I tried to PM you but I did not see the option to in this forum. If you could email me or something that'd be great! surfphotosd at gmail dot com.

Thanks again!
I just read this post on the 6.2 fuel economy I will keep it in mind very helpfull thanks
Vince:cool:

[Quartermiler6]

What about machining an adapter to use an electrically controlled fan clutch such as this. http://www.summitracing.com/parts/HDA-3264/

You would just wire it through an electric fan switch and thermocouple. It wouldn't pull nearly the amps as an electric fan, and you could possibly pull as much CFM through the radiator as the stock fan. The plus would be almost zero parasitic drag from the fan clutch. The guys on the Cummins pages also install switches to activate them while in traffic to keep air flowing through the A/C condenser. What do you guys think? Maybe worth a few MPG's?

[TaxiVan]

Lots of interesting replies in this thread -- I am considering a 6.2L diesel swap for my GMC Safari van... I use it in my taxi business... 84Blazer mentioned a cabbie talking about gasoline costs and wondered why GM never built 6.5 diesel Caprices for taxi specials... #1 Reason - EPA's EcoNazis and the rest of the tree-hugging, earth-worshipping yuppie world.

Truth be told, quite a few (number unknown) FBI fleet-package Impalas were factory fitted with either the 5.7 Olds or the 6.2 Detroit somewhere around 80-84. My guess would be that leftover warranty 5.7s went first... One of these cars is on YouTube.

I had been considering a swap using a 3.9L Isuzu NPR truck engine, but plans tend to change when your bread and butter unexpectedly dies, and you have to get creative.

It actually seems the 6.2 will actually be a better/easier swap than a 3.9L Isuzu. No trans adapters required, uses standard Chevrolet engine mounts, and no electronic or emissions BS like the 4.3 V6 I currently have.

Truthfully, from my research, I wouldn't be scared to use a 4.3 V6 Oldsmobile diesel (they were the best of the three, having 14 head bolts) with a 200-4R or 700-R4 automatic overdrive.... but these diesels are hard to find, and I already have a 6.2.

[76diesel]

I get 40 mpg out of a 6.2 diesel non turbo engine. I put the engine in a camaro, installed a 700r4 with lockup torque converter and put a 2.73 rear gear.

I love this car, it is fast, great fuel mileage on the highway and the most fun car I ever drove.



http://www.youtube.com/watch?v=m6W5DfuWQBs&list=UUcstH9ogtnkZPmMUGIiTg9w&index=6

[More Power]

Cool! Looks like it fits beneath the hood quite well. Amazing what a lightweight and aerodynamic vehicle can do with a 6.2 for fuel economy.

I like the radio commentary playing in the background of your video.... ;)

Welcome to the board.

Jim

[DmaxMaverick]

VERY nice! Thanks for sharing.

[joeq]

I like a guy with an imagination. Very clean looking install. I can hear the purists on the Camaro forums now. :eek: :D. You must be a very patient and inquisitive individual. I nominate you for the Nobel Peace prize. Or maybe an Oscar...(or something like that). What's next? Walking a tight-rope over the Grand Canyon?