Max fuel economy for the 6.5TD [Archive] - TheDieselPage.com Forums

More Power

12-23-2004, 15:31

We started a fuel economy thread over in the 6.2L forum that has become very interesting. What I'd like to do here in the 6.5TD forum is through cooperative effort suggest ways to build and run a 6.5L Turbo Diesel for maximum fuel economy.

Scenario #1- You're willing to go inside the engine to make changes designed to improve fuel economy, and you're willing to perform some modifications to your vehicle. This scenario compromises other vehicle uses in ways to maximize fuel economy.

Scenario #2- You use your 6.5TD for a variety of family and work related driving. From city traffic to long Interstate trips, you're looking for maximum fuel economy without compromising too much in vehicle versatility.

Scenario #3- You use your 6.5 to tow 5-10K trailers several times per year, so power and durability are equally important to fuel economy.

Let's begin our discussion with scenario #1.....

MP

ucdavis

12-23-2004, 17:37

Timing gears would be a good start to eliminate the slop between programmed timing & actual.

A well balanced fuel curve (chip/reflash) would seem logical, taking boost into account to trim fuel to the max that would take advantage of air pumped into IM. There's a point where adding fuel churns out more heat, but no more go-go. That probably dovetails w/req'mt for an intercooler to allow boost above 5-6psi. I'll defer to the chip programmers for additional commentary.

Intake air path needs serious opening; consider a conical racing type air filter; may need to augment filtration on a gas unit to get the square inches but still have the filtration.

Water injection is well worth consideration; gives both cooler intake air (so you could add boost) & added expansion potential in the cylinder, but uses no fuel. For fuel efficiency as an overriding objective, I'd say H2O injection is probably more productive than air-to-air intercooling. But you have to fill the water tank, & give up the space for it. Always a trade off.

Torque converter lock up mod.

Port matching. Port polishing for the meticulous.

DA BIG ONE

12-27-2004, 08:16

I use my SUB for traveling, seldome tow and always on it around town. Just returned to Palm Beach from Tombstone average mpg was 26, this is with Heaths program and larger injectors.

My gear change to 3.42:1 was the most productive for extra MPG. Because of the torque I hardly notice any change in low end performance.

I am now considering going to AT 33.5" tires which would bring my rear ratio down to about 3.10:1 and just below max torque at highway speeds.

After many mods, I am looking towards a 300 hp mech. injection pump, and stand alone transmission controller, I am thinking tweeking from here should yield slightly more mpg, I hope.

moondoggie

12-27-2004, 11:21

Good Day!

Someone mentioned elsewhere, probably in the 6.2 version of this topic, that prechamber cups might help mpg. Experts?

Gears! My 95 pickup gained a pretty solid 2 mpg after I installed the Gear Vendors Aux. OD. You might want to look at an earlier post of mine. If the truck is 2WD (which by itself should help mpg), maybe it wouldn't be too far out of line for a max. mpg truck to go to a lighter 3.08 set of gears? Again, experts?
Is it possible that factory wastegate programming might be best? In other words, does spinning the turbo waste power, as long as there's adequate combustion air getting to the engine? I'm referring to the way our trucks pull boost over 1800 rpm under certain other conditions, which is anathema to making more power, & maybe even bad for exhaust gas temps.</font>I can't WAIT to see where this goes.

Blessings!

Brian Johnson, #5044

David Brady

12-27-2004, 12:39

I have put a set of 2.73 gears in that does allow the lower rpms but I haven't adjusted the VSSB yet to track fuel use. It does allow me to comfortably keep up with traffic in the fast lane. I have wondered about the fuel useage between my old 6.2 and the 6.5. I think the reason that I don't see much better mpg is the increased power is easy to use and will require more fuel. My 6.2 ran at WOT for many miles but didn't produce power or use fuel. I just wish I had access to this site back then.

More Power

12-27-2004, 15:01

Recipe for maximum fuel economy:

1- Engine dynamically balanced and carefully assembled using stock CR pistons/gapless rings.
2- Cyl heads with 1982-1993 6.2L "C" series precups.
3- DSG - Phaser or gear drive timing set.
4- If DS4, set TDC-Offset to -1.94. If DB2-4911, set timing up to 5 degrees BTDC.
5- Hi-pop injectors.
6- Free flowing exhaust - including port matched exhaust manifolds and 3-1/2" mandrel-bent exhaust system.
7- Turbo set to produce 3-5 psi at a 65-mph cruise.
8- A 4" lowered 2WD 1500 series truck/Sub with an under-bumper air dam, and riding on stock size radial rubber at max air pressure.
9- Geared for 1800-rpm at 65-mph.

25-mpg+

MP

catmandoo

12-27-2004, 20:07

mp my current truck is a 92 c1500 ext shortbox,it has a crate 6.5 n/a with 160,000 on it,i have touched nothing on this engine since i got it 2 yrs ago,with 60,000 on the engine.it also has the nv4500 5spd and 3:08 gears.the only major things i have done is add my banks turbo onto a factory turbo exhaust manifold and a mandrel downpipe with 3 inch all the way back,without muffler.i can run 25mpg all day long at 65,and thats where it wants to run but my boost is down around 1 1/2 lb,and as you mentioned running boost around 3-5 lbs at 65,thats what i'm after,i figure if i can get the boost up right off idle,it will increase my milage,even if i run at 55 the engine seems to sound like it's laboring yet it will pull up to 27mpg,and it's still running a boost 1/2 to 3/4 lb. i believe there is milage there to be gained by upping the boost in that 3-5 lb range but i don't think much over that 5 lbs at cruise is gonna show much more if any appreciable gain.i'm currently gathering parts to do a major change come spring,i want to drop 2 inchs in the front and 3-4 in the back,get rid of the elephant ear mirrors for some suburban units,maybe toss the rear bumper and put on a rollpan.my goal is 30mpg,and i think it is attainable.i may just get that thru the aero changes.but i would like to get my boost up first.

G. Gearloose

12-28-2004, 06:44

Your lack of boost is just an indicater that your not using much HP to roll.

Strap a sheet of plywood to your bumper and your boost will double or triple.

grape

12-28-2004, 08:58

change the exhaust housing. call dave at majestic turbo in dallas and tell him what you have, and that you want a .81 A/R euro mount p trim exhaust housing.

catmandoo

12-28-2004, 14:54

plywood ,i like that,and thanks grape i'll give him a call.you wouldn't by chance have his number??

Govt issue

12-30-2004, 12:45

98 k2500 burb stock and I mean stock. 265/75/16 3.73 6 people 600 miles 55-75 mph was 16- 18 mpg used miliage off of lead car, bigger tires.

johnny2can

01-01-2005, 00:21

Originally posted by More Power:
Recipe for maximum fuel economy:Hey, MP (or anyone else)... I know there are several companies out there that build nice replacement 6.5's... are there any that do items 1-5 in one package? I imagine the heads would be the most unusual thing to include in a package...

gmenor

01-02-2005, 13:31

MP,
Can you elaborate on what you mean by "Geared for 1800-rpm at 65-mph"? At 65 mph I'm running 2000 rpm, what can be down to lower the rpm's?

johnny2can

01-02-2005, 15:04

Originally posted by gmenor:
"Geared for 1800-rpm at 65-mph"?He means that if you are running at 65 mph, your engine is turning at 1800 RPM (the MPG sweet spot for our engines, I believe)

Without going into the math (several posts here and elsewhere on the 'net) your tire size, differential ratio, transmission ratio (and auxiliary transmission ratio, if you spend the money for one) all affect engine speed at a given road speed.

I run 2000 at 60 mph and would like to lower it (I assume that a) my tach is correct and b) my speedo is correct... have yet to verify both).

- I'm already running 265/75's and have no desire to go to a larger tire.
- I considered dropping my diff ratio from 4.10 to 3.73, but a) I'll lose some grunt when I start hauling and b) I'd have to do the front diff too and it would only drop it to 1850 (close, but I'm a perfectionist).
- not gonna mess with the tranny until it goes out (if ever) so I'm stuck with the .75 (or .78, I can't remember) OD ratio.
- planning to go with an auxiliary transmission (Gear Vendors or US Gear). IIRC, should drop my final engine speed closer to 1800 *and* I get to keep my low-end grunt.

Hope that helps!
-John

JoeyD

01-02-2005, 16:58

As far as motor mods , balancing, use of coatings on all moving parts to lower friction, windage tray with a scraper, coating the exhaust manifolds as well as the exhaust pipes, turbo blanket to trap the heat. I'm sure there are a few things I forgot that need to be mentioned but making the basic motor itself as efficient as possible can only help with the milage.
I would also make a guess that a timing gear will create a slight bit more of friction compaered to a chain.
My own best milage in my truck with cap on and with a weight of 6500lbs is 22.5mpg. This was over 1200 mile round trip

moondoggie

01-04-2005, 11:17

Good Day!

More Power: Would it help or hinder this topic to report our mpg results, relating them to our equipment, etc.?

Blessings!

Brian Johnson, #5044

kowsoc

01-05-2005, 21:03

I think the friction of gears vs chain is meaningless when the majority of friction is in the piston and ring assemblies. Remember that at 2400 RPM they go up and down 40 times per second....times 8 cylinders! Brings me to a point. Since the rings have to scrape the oil off the cylinder to prevent oil consumption, a lighter viscosity oil is easier to scrape off and is said to increase fuel economy. That's probably why some of the new gas jobs are calling for a 5w-20. But for a high compression diesel I still think a higher viscosity should provide better protection...especially when under loads such as towing.
......just my .02 cents...... smile.gif

moondoggie

01-06-2005, 06:35

Good Day!

"But for a high compression diesel I still think a higher viscosity should provide better protection..." My very old & very weak understanding of oil viscosity tells me that the "W" number is the viscosity at 0

jdmetcalf57

01-06-2005, 17:33

I recently added gages to my truck to read boost, back pressure, vacuum on the wastegate and fuel pressure. I just returned from a trip to the FL Keys and did some experimenting on the trip. One interesting thing surprised me. I normally pull about 4k with about 2k in the truck bed and drive 70 on the interstate. I am geared to run about 2050 at this speed. The back pressure is always higher than the boost by at least 2 psi. Stock boost settings gave level road readings of 3-4psi boost and 5-6 psi back pressure. I got on all tanks of fuel 14.5 to 15 mpg except the following.

On one tank I adjusted my homemade boost fooler to get a about 5-6 psi boost which gave 8-10 psi back pressure. This tank I got 14 mpg. The worst on the trip.

I also removed the vacuum hose from the waste gate to see how much back pressure I had just from the open exhaust and it was less than 1psi.

I think a more efficient turbo would help mpg. My gages have both been calibrated at 5 psi so I know the readings are pretty accurate.

One other thing the vacuum gage shows about 7" of vacuum under stock boost at my driving conditions. With more throttle or idle it goes up significantly.

These mileage figures are the best I've ever got. On similar trips with the truck stock I got about 11 mpg.

moondoggie

01-07-2005, 07:10

Good Day!

"I got on all tanks of fuel 14.5 to 15 mpg except the following." "These mileage figures are the best I've ever got. On similar trips with the truck stock I got about 11 mpg." It's unclear to me what you changed that caused this major improvement in mpg. What did you do different to get 14.5 - 15 from when you were getting 11? I'd do just about anything within reason to achieve such an improvement. I'm not completely unhappy with my mpg unloaded, but only got 12 - 16 pulling our US Cargo SM625TA2 trailer (looks like the US Cargo SM727TA2 (http://www.uscargo.com/uscargo/products/enclosed/snowmate.asp) [Click in colored text] except it's 25' long instead of 27'), which isn't much of a load.

Thanks & Blessings!

Brian Johnson, #5044

jdmetcalf57

01-07-2005, 09:57

When I bought the truck it was a k3500 drw auto trans stock exhaust with 4.10 rearend.

I have changed the following that has increased fuel economy.

Change the TDC learn to -1.8. about +.25

Replaced the exhaust from the down tube back with 3.5 in mandrel bent exhaust. about +.5 mpg

Replaced the rear end with 3.73 and increased tire dia. to give equivalent of 3.43. about +1mpg

Removed bug shield. about +.1-.25

Use fuel conditioner. about +.25

Change to single rear wheels. about +1

Replace the auto with a NV4500 manual. about +1

Use all synthetic oils except the engine. about +.25

I have experimented with higher boost and water injection but have not been able to see any mpg gains with these the way I drive.

The above mileage gains may not quite add up but over all I think they contribute in about these proportions. I am hoping this summer to hit 16mpg pulling my camper with summer fuel since I have hit 15 with winter fuel.

coldtruk

01-08-2005, 11:49

Hello,
Thought this might help with understanding the "oil Doughnut" information (on the cap of the container) according to chevron and its applications with diesels per oil type and usage, hope its helpfull.

http://www.chevron.ca/ProductsServices/Retail/MotorOilLabel.htm

Good day

coldtruk

markrinker

01-08-2005, 11:58

I would estimate my average mileage for either truck with trailer loaded or empty to be about 9-10 mpg. Empty without trailer (rarity) is about 10-11.

Have done lots of mods to #2 and experimented with tire sizes. 4.10s cost me some, but I never drive under 65 which is probably more of the issue.

moondoggie

01-10-2005, 09:00

Good Day!

jdmetcalf57: Thanks!

Blessings!

Brian Johnson, #5044

johnny2can

01-10-2005, 20:38

Originally posted by Mark Rinker:
but I never drive under 65 which is probably more of the issue. Interesting you should say that... recently went on a trip and noticed a *HUGE* difference between 65 and 70... on the order of 3 MPG... was getting 13 in a hurry (>=70), but 16 when taking my time (<=65)... The difference, while noticeable, is not so drastic in my gasser 'burb, which lines up with what I've read on this site and others.

aerodynamics of a brick... ;)

moondoggie

01-11-2005, 08:57

Good Day!

I too have noticed that my trucks seem to like 65 mph or less, for good mpg. At 70 mph, it seems like you can watch the gauge go down. Sure wish I could generate some hard data.

Aerodynamic drag increases as the square of speed, so an increase in speed of ≈ 7.7% (65 > 70 mph) causes an increase in aerodynamic drag of ≈ 16.0%. Is that enough to account for how much mpg drop we're seeing?

Blessings!

Brian Johnson, #5044

jdmetcalf57

01-11-2005, 09:37

The amount of mpg reduction from 65 to 70 will be highly dependent on what you are pulling. Aerodynamic drag, and rolling friction contribute to fuel consumption. The data I've seen at those speeds a semi has about equal rolling and aero drag.

There takes a major portion of fuel to turn the engine over. If you have a computer to monitor check how much fuel is being used when in neutral and 2000 rpm. I think my truck is around 16-18mm*3/fire. If you back figure based on average mpg when I am cruising I am using 36mm*3/fire pulling my typical load of my 4K camper.

As you can see from this just turning the motor over takes a substantial amount of fuel and Hp. From this fuel rate I have estimated this hp to be 50-60.

From this discussion you can see that aerodynamics is just a portion of fuel usage in my case probably around 40%

The cummins website has some interesting data on fuel economy and semis.

moondoggie

01-19-2005, 05:27

Good Day!

Scenario #2 (You use your 6.5TD for a variety of family and work related driving. From city traffic to long Interstate trips, you're looking for maximum fuel economy without compromising too much in vehicle versatility.) & Scenario #3 (You use your 6.5 to tow 5-10K trailers several times per year, so power and durability are equally important to fuel economy.) interest me most.

Back on 27 Dec 04, I asked, "...does spinning the turbo waste power, as long as there's adequate combustion air getting to the engine?" I was hoping our many experts might have some ideas here.

It appears from a couple years of reading what I could on the Page, lots of boost reduces EGT (assuming charge air cooling), presumably by moving more air through the cylinder than is necessary for complete combustion, allowing this extra air to cool the EGT into a safe area. If this is so, it makes for longer engine life.

Isn't it also possible then that, when operating at low loads (no trailer or such), that too much boost might waste power by spinning the turbo way faster than it needs to be spun? In other words, the load is light, so boosting beyond what's needed for complete combustion wastes power spinning the turbo?

If this is so, it wouldn't be impossible to build a controller that controlled the wastegate as a function of EGT. In other words, control the wastegate to hold EGT at 900 F (or whatever temp. was determined to produced best combustion for best mpg) while cruising.

If this is a really stupid idea, have a laugh at my expense. I know pretty close to nothing about these engines; the little I have learned has been here on the Page.

Blessings!

Brian Johnson

BigDiesel

01-19-2005, 11:24

Originally posted by More Power:
Recipe for maximum fuel economy:

1- Engine dynamically balanced and carefully assembled using stock CR pistons/gapless rings.
2- Cyl heads with 1982-1993 6.2L "C" series precups.
MP Two questions here
1)I was under the impression that everyone was wanting 18:1 pistons, especially if turning up the boost.
2)Will using the latest heads (2002+)have that much less effect? What is the deal with 6.2 "C" series precup heads?
Dave

damork

01-20-2005, 18:56

I didn't see thermostat temperature mentioned. I've experienced the best economy when the engine is running hotter, with at least a 195F thermostat, with 21 mpg being my best with the temp gauge sitting at about 200F cruising at 65 mph (not towing).

David Brady

01-20-2005, 19:17

Has anyone been able to experiment with a set of Direct injection heads? Seems like that would help economy as well as power. :confused:

johnny2can

01-22-2005, 22:51

Originally posted by damork:
I didn't see thermostat temperature mentioned. I've experienced the best economy when the engine is running hotter, with at least a 195F thermostat, with 21 mpg being my best with the temp gauge sitting at about 200F cruising at 65 mph (not towing). I've *read* that mileage goes up with higher coolant temps (ala Evans waterless coolant...) and last summer experienced it on my gasser 'burb. Stat failed at the beginning of long trip... Running at a consistent 235* to 240* increased my mileage by almost 2 mpg over similar trips in the past. I almost hated to replace the stat... ;)

I've seen many posts recommending running 185* stats, but as long as you keep your critical temps in control (EGT, tranny, oil, PMD, etc.), and you run an additive to keep your IP lubed, what's wrong with running a higher temp on these machines?

Running a higher temp stat would even help those pulling heavy loads, I would think, because the higher temp differential (between radiator and air) would cause faster heat transfer allowing more heat to be rejected for a given ambient temp (again with the above assumptions).

My 6.5 stats are failing now (too cool) and so I plan to put in 195* or 200* (if I can find it)...

kowsoc

01-31-2005, 19:38

I've also experienced better fuel economy when the engine is warmer. In the winter I have the grill and bumper holes blocked completely to keep the under hood temperatures up. I am running a 195 stat but I believe there are 205's available.

More Power

01-31-2005, 21:02

Big Diesel, Since this thread is primarily concerned with fuel economy, I recommended the 6.2L "C" series cylinder head precups. These use a smaller port that the flame passes through between the precup and the piston, which tends to increase velocity, swirl and combustion efficiency. The 6.5L TD uses larger ports, which tend to help with power at higher manifold pressures. If I were building a "power" engine, I'd want the biggest TD precups.

Thermostats - In a pure economy engine, a higher t-stat rating might help.

In a 6.5TD that tows or is run hard, I personally would want cooler t-stats. This helps with transmission temperature, allows more cushion for engine coolant temperature and is kinder to the electronics (FSD). A case could also be made for cooler intake air (passing through the intake manifold) and cooler fuel, which might be a slight plus.

There's some good debate here about fuel economy. Keep it going! The collective experience of everyone adds to the goal of improving fuel economy.... smile.gif

MP

G. Gearloose

02-01-2005, 03:57

Originally posted by johnny2can:
I would think, because the higher temp differential (between radiator and air) would cause faster heat transfer allowing more heat to be rejected for a given ambient temp (again with the above assumptions).
[/QB]All thing being equal, I concur, but they are not... my observations are an 185 RS tstat opens wider at 190 degrees than a 195 AC or RS tstat opens at 210. Others have observed similar. Perhaps they open more at higher temps under pressure, but I suspect not.

rjschoolcraft

02-01-2005, 05:29

This is slightly off topic...

I've found that the cooling system on these engines is marginal at best. MP's comments are right on with my experience for anyone who works his 6.5TD hard, as I do. Read the 6.5TD Cooling Solutions That Work (http://www.thedieselpage.com/members/features/65cooltipsc.htm) article. Logic and diesel theory argue for higher temp stats, but practical experience with this particular system says no...especially if you tow heavy in the Western United States.

There are those who will argue vehemently against me here on this subject. You draw your own conclusions.

For a purely mileage driven decision on a truck that doesn't tow...the 195's would probably be the best choice.

Billman

02-01-2005, 13:27

I currently have a 205* thermostat in my daily driver(gas). It has improved mileage 1.5 over a 195*. I check it religiously.

Although I don't have the Practical experience that you do Ron, I disagree. I also don't tow in the Western United States.

If you ever find that 205 thermostat kowsoc, please let us know. I have come up empty.

Without towing, I block my radiator for 7 months out of the year in order to achieve maximum fuel economy/(efficiency?)

Marty Lau

02-07-2005, 10:43

Thought I would put my .02 in here. I have gotten as high as 24.5mpg and see 20 mpg regular. My best was achieved cruising at 55mph across Norther AZ before the speed limit there was raised to 65. Aerodynaic drag is VERY important. If you add extra's to you rig like bug sheilds running boards, visors, bigger mirrors they will add drag and increase the need for power to over come the added drag, more power means more fuel used. As you increase speed aerodynamic drag increase by the square which increases need power by the square. In other words if double you speed from say 50 mph and it takes say 40 hp to travel at that speed and you double the speed you are traveling at to 100 mph it will take 4 times as much power or 160 hp not double. This is why bumping your speed up increases your fuel useage so much. So if if your in a mode trying to get max fuel ecconomy then slowing down from 80 mph to 65 will make a difference. This is also why GM spneds so much time and money in wind tunnels refining designs to reduce drag. Auto makers have no also designed new Pickup trucks so that the tailgate produces no extra drag so taking the tailgate of or down will not produce better mileage.

jdmetcalf57

02-08-2005, 03:54

16ga 4x4

Aerodynamic drag is not near all the drag however when only considering this drag. The power goes up by the cube of the speed. Or 2xs the speed needs 8xs the HP for just the aero portions. The aero drag force goes up with the square of the speed but since Power=speed x force. Hp is proportional to V^3.

However since you are moving faster and if you assume fuel usage is somewhat proportional to HP output. MPG for just the aero part goes down approximately as the sqare of speed.

From this you can see that as speed continues to increase aerodynamics becomes more of the dominating factor.

Marty Lau

02-09-2005, 13:17

jdmetcalf57;
You and I are on the sme page, I don't know the exact math just what I learned in my pilot training. The we are both making is that the faster you go the more the areo drag affects things that is part of the reason MPG drop off. The basics is to get more HP you burn more fuel pure and simple and the increase speed is not ofset by increased fuel burn. Just as any round trip with a wind will take more time and fuel than a no wind condition.

moondoggie

02-10-2005, 10:07

Good Day!

My memory is pretty foggy, but I thought aero drag was proportional to the square of speed, not the cube, but if wrong, it won't be the 1st time... :(

From REALLY foggy memory, they used to say that the best mpg generally occurred where rolling resistance equalled aero drag, which was (for most cars) ~ 35 mph or so. At this point, aero drag was increasing so quickly it dominated mpg.

In fact, I also remember reading that rolling resistance was generally constant, & actually drops some at higher speeds. It drops so little that it's massively overwhelmed by aero drag increases, however.

I have no idea where drivetrain friction works into this.

My personal experience is that my mph drops dramatically as speed increases, which would support aero drag being the dominating factor.

Keep in mind, ALL the above is from the memory of a guy that can't remember what he had for lunch yesterday. ;)

Keep the good ideas coming - mpg is my life.

Blessings!

Brian Johnson, # 5044

rjschoolcraft

02-10-2005, 10:34

The drag force does go up with the square of the speed. The power required to propel a vehicle against that force goes up with the cube of the speed, as was astutely pointed out above.

Back when I worked on the Joint Strike Fighter preliminary design, I had to do a bunch of preliminary sizing on fans and clutches as we were trying to settle on a configuration. For the clutch and gear train, I needed to know how much power it took to drive a fan at various speeds. The aero guys gave me curves of windage torque vs. speed and windage power vs. speed... Torque increased with the square of the speed and power increased with the cube of the speed. This directly correlates to what is being discussed here.

MJEasly

02-10-2005, 12:17

From what has been discussed here, it sounds like an electronic air suspension that will lower your truck a couple inches for highway cruising might not be a bad idea. You could also have normal mode for stock height and a 4x4 mode that raises it a few inches for off-roading. IFS throws a wrench into it, but you could always do a full axle swap.

moondoggie

02-11-2005, 13:49

Good Day!

MJEasly said, "...it sounds like an electronic air suspension that will lower your truck a couple inches for highway cruising might not be a bad idea." I think there may be cars on the road that already do this. In fact, I remember reading somewhere a long time ago that belly pans would help mpg too, they're just impractical.

ronniejoe: Next time we meet, I'm gonna get you to explain to me (if that's possible, I'm pretty dense ;) ) how aero drag increases as the square, but the power to overcome it increases as the cube. (I suspect it'll either be a forhead-slapper or I'll never get it.)

Blessings!

Brian Johnson, # 5044

chickenhunterbob

02-11-2005, 17:44

My driving is pretty much strictly scenario #2.

City miles are minimal, mostly highway, and no towing to speak of.

On the highway I can average 23 - 25 MPG in Canada, with occasional highs of 27. This with the tach at around 1900.

On the US interstate I-29 two weeks ago between here and Nebraska, I recorded a dismal 19 (75 MPH speed limit and a real strong south west wind). Tach on 2400 at 75 MPH, the old truck never knew what hit it. And me as a fuel mizer, I was ashamed of myself, at least somewhat, but shaved a couple hours off the time to get there.

Not so big of a rush to get home, even though took an hour or two longer, slow to 65 MPH and 24 MPG, tach still around 2000.

A previous post a few months back (may have been Moondoggie, not 100% sure) suggested before cleaning out the bank account to overhaul your truck to increase MPG, figure how much you could gain vs how much you spend.

I did the math at the time, and for me with the price of fuel as it was a couple months ago or more when that thread was up and running, if I spent 1000.00 on a 1 MPG increase, I could recover that amount in fuel savings in 140,000 miles. Well, not likely the truck will live that long, so for me, any opening of the engine, aftermarket exhaust, etc. would never pay for itself in fuel.

lots of mods "claim" higher mileage, but if you read this board, everyone who does any mods at all seems to gain weight on the right leg immediately, and I haven't heard of any drastic fuel mileage increases.

Maybe if my truck was newer, and had 300K ahead of it, there may be some benefit. But to me, I CAN drive 100KPH, and will, and will hopefully continue to be happy with the mileage.

moondoggie

02-14-2005, 04:24

Good Day!

chickenhunterbob: Is that mpg in US or Canadian gallons? If it's US, that's some of the best mph I've ever heard of, :eek: & I'm WAY jealous. :D

Blessings!

Brian Johnson, # 5044

rjwest

02-14-2005, 05:27

With my truck camper, The fuel rate increases Dramaticaly from 60-70 MPH,

If I tuck in behind a Tractor/Trailer, I see a
2 MPG increase ( Instant readings )
13.0 to about 15.0
Also ( my opinion ) That if I can get a run at a hill and ease off the throttle on the climb,
I can get a slight increase in mpg

This technique worked very well on my old 6.2 N/A
with the mech IP, but quite difficult on the elect
IP.

My Total average with a 3000 lb truck camper is
slightly less than 13.o mpg US

The headwinds KILL ME though....

chickenhunterbob

02-14-2005, 15:25

Moondoggie,

Those calculations are in imperial gallons.

My mileage, X .833 would give the corresponding figure in US gallons. Miles are the same wherever you go.

Up here, fuel mileage is calculated in litres per 100 kilometers, but I'm too old for that, I always convert to MPG which is a meaningful figure to me.

Bob

eracers999

02-15-2005, 05:43

Dont have hard no's yet but after i built this new engine and have over 1k mi on it i have started to check fuel mi. The old motor was getting fuel at 325 mi. The new motor is at 302 mi and the fuel guage is just under a 1/2 tank.
That is a lot more fuel and i have a lot of messing around on this tank and was expecting the no"s not to be too good. So far i am very suprised at how much less fuel has been used.

Engine has much better torq, and cruises at 70 mph with muck less effort. So tickled am i over the end result of this project.

Kent

moondoggie

02-15-2005, 09:38

Good Day!

[i]

DmaxMaverick

04-20-2005, 15:33

Bumped up for Frijoli.

rjwest

05-12-2005, 13:12

16 ga you might want to rethink the reason for the more time/fuel used in flight , not related to drag, just amount of time in Head wind condition.

Marty Lau

05-13-2005, 08:22

Originally posted by rjwest:
16 ga you might want to rethink the reason for the more time/fuel used in flight , not related to drag, just amount of time in Head wind condition. Yes I know I was a CFII for a number of years, but when you figure fuel consumption it's with regard to time in Aviation. The point is that many people are on a false belief that if you have wind the round trip is the same just on way is faster and the other is slower. They do not equal out. I have had people insist that if they go faster that their fuel consumtion for the trip will not increase beause yes they are burning more fuel per hour but they are covering more ground in that hour.
I have also had people tell me that wind does not make a difference in the time enroute on a round trip because the faster leg negates the slower leg..... :eek: both false. I have had have to go as far as make people (or do them for them)do the calculations to prove the point.

[ 05-13-2005, 08:32 AM: Message edited by: 16ga SxS ]

rjwest

05-13-2005, 12:23

Ditto: Agree, same with 90 degree crosswind
still more fuel used...Come to think of it.I guess it works that way in a truck also.

GMC Hauler

05-15-2005, 17:10

I recently changed out the rims on my Suburban to new rims that were take off's from a newer truck (click on my page to see pictures). The rims are 20 # lighter each. I changed tire sizes at the same time. I had 265/75R16 load range C. I wanted to put the correct load range on, and a slightly narrower tire, so I went with a 235/85R16 load range E.

Tire size is barely different, but I wanted to calibrate the VSSB (vehicle speed sensor buffer) anyway. Last time I calibrated it, I used road mile marker signs. This time, I used a GPS unit.

I found that my speedometer was reading 1 1/2 to 2 mph slower than the GPS reading. I readjusted the VSSB (per 1999 feature articles and product reviews) several times until calibrating the speedometer dead on. The spedometer reading slower than actual speed has several affects which affect gas mileage.

The first is that indicated miles will be lower than actual miles. This will cause your computed mileage to read lower than it actually is. Readjusting the VSSB will cause this to read correctly. This doesn't improve actual mileage.

Secondly, most of us drive to the speed limit, or a value above, e.g 5 mph above posted speed limit. If your indicated speed is low, you will in actuality be driving faster to make your indicated speed meet your desired drive speed. This has the effect of making your actual speed higher which reduces your gas mileage.

I was lucky to have a VSSB that was reprogrammable. Maybe those of who have changed tire size or arent sure should take a look at our calibration.

[ 06-06-2005, 10:10 AM: Message edited by: GMC Hauler ]

moondoggie

06-13-2005, 09:29

Good Day!

More Power: Any chance this will become an article? (You know me & mpg...) :D

Blessings!

kowsoc

06-14-2005, 18:26

I put on a lot of km's so fuel economy is also important to me. I would also like to see more information on this subject. I believe one was in the works regarding fuel economy and different fuel additives. So far I personally have found Power Service to give me the best, 26.2 mpg imperial....21.8 U.S. mpg at 65 MPH empty.

Marty Lau

06-15-2005, 11:15

Originally posted by kowsoc:
I put on a lot of km's so fuel economy is also important to me. I would also like to see more information on this subject. I believe one was in the works regarding fuel economy and different fuel additives. So far I personally have found Power Service to give me the best, 26.2 mpg imperial....21.8 U.S. mpg at 65 MPH empty. Kowsoc; your doing real well give yourself a pat on the back. :cool:
How about putting your truck info in your signture so we can see what your driving Sir?

ees

06-16-2005, 02:34

All these numbers everyone is posting is making me sad. Our first road trip in this vehicle a month ago netted the same fuel econ we get around town. 15.5 mpg. Now we were running 70 t 75 all the time, but no trailers and only 2 adults and a 2 year old so not much weight.

I have never had my injection timing checked. I think that might help. I didn't notice anyone talking about that in this thread, but I might have missed it.

kevin77

06-16-2005, 04:31

Hey ess - I have a 94' burb and I only average 15 to 15.5 - with 3.73's - I have done the cooling mods so far but next I want to get the truck breathing, (intake and new exhaust) new injectors and glows (I'm pretty sure the injectors are old and worn) than gauges and a new chip. I think that once I get some new parts on mine, the mpg will go up.

KEvin

ees

06-16-2005, 13:12

Good to know I am not alone. I also have 3.73s, but I have new injectors. My next step is water injection because I can feel a big difference on warmer days. I have Heaths turbo master? (spring loaded waste gate control) set at stock levels, but I still think I am loosing power from intake temps.

More Power

01-10-2006, 15:40

Things like engine rpm, vehicle weight & drag, and driving strategies for max fuel economy will apply to just about any light diesel engine. Our vehicle choices affect weight and drag, and have an effect 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 all of them here. Some components you may already know about, but there are a few you probably don't… At least not yet!

Jim

ogrice

01-10-2006, 16:25

The Max MPG project uses a 72 El Camino. I have a 56' Ranchero that I wish to put a 6.5td or a 7.3psd in. Under the hood is a 352 FE, and the car has been sitting for the last 20+ years in the garage. Big project, a full restoration, but i'm going to do what it takes to get it back on the road.

Robyn

01-15-2006, 10:07

In reading here I see a lot mentioned about back pressure. If your engine is fighting back pressure you need to address it. The muffler in stock rigs is most likely a big part of this as well as the catylitic converter. Now if you live in an area that monitors this stuff you cant remove it but there are better units that will flow better. Take for example the big trucks, we run 500 HP caterpillars in our big trucks and they breath out through a 5 inch main from the turbo into a Y pipe and split to two 5 inchers up the stacks and out the top. There is very little back pressure here at all.
If you are seeing more back pressure than boost you need to be opening up the exhaust to let the little beastie breath. The retained heat alone is not doing the engine any good.
Just a thought.

Marty Lau

01-17-2006, 16:26

How about adding AIRTABS, http://www.airtab.com/
they claim a 4-8% increase of MPG with them. If your getting 25MPG that is a full MPG increase. I been think about adding this to my truck for
S's&G's.

Truckie117

01-19-2006, 02:56

Hey Guy's
I am jelous of the milage. I run stock and I mean really stock.I calculate milage every time I fill up and usally get 15.5 to 16.5 for all around diriving hiway street NY bumper to bumper 495 stuff. The best milage I got was when I drove the truck back from VA dealership 20mpg 2 Pump chages and lota miles later 16.5 is the best I can do at fastest 65mph 2000rpms. Would like to up this with the price of fuel. :eek:

skittle

10-04-2007, 22:40

The only thing left out of the discussion about the affects of faster travel speed... is the simple fact that most of these vehicles are geared to run somewhere well above the optimum 1800 rpm and as you increase travel speed you also increase engine speed. Since the engine efficiency drops off quickly as engine speed increases above 1800 rpm, the faster travel speeds really hurt. A simple test would be to compare fuel economy at the same engine rpm in direct vs. overdrive. That would show you the areo and friction stuff, excluding the engine and some of the transmision. I have lots of mpg data on a stock 1995 1/2 ton 4wd 6.5 turbo with 3.42's. I couldn't tell you what the mileage is at 65 mph, I've never done that! My year around average is about 14.5 mpg. Less when towing (11 ish) and more when not towing, especially at 70-75 mph (16.5 ish). Enuf for my first post.

More Power

10-05-2007, 09:13

Welcome to the board!

I've long held that 1800-RPM and 65-MPH are magic numbers for best fuel economy. The engine's torque peak will appear at 1800-1900 RPM and wind resistance at 65-MPH is still manageable, yet allow you to travel at a realistic speed.

Jim

Nobby

10-06-2007, 07:11

Makes sense to me with 3.42's and 265's i'm in that 1800 to 2000 rev band and it feels real sweet right there. I see somewhere around 18 - 19mpg, i should point out that I do alot of long distance driving and my foot is not made out of lead. I am just installing a 4" exhaust and hoping to maybe break the 20mpg barrier. Not sure if my foot will stay unleaded tho!

To me if I had the money an underdrive with my current setup would be a sweet rig that covers all bases. If I had that kind of money a Duramax would probably make more sense tho.

cheers
Nobby

6.5 Detroit Diesel

10-06-2007, 10:20

There was a lot of discussion about how bigger tires cut down milage. I agree that with a typical small gasser engine, this would be the case. However, the diesel puts out so much torque that I don't feel it affects milage. I am running the 36" Military mudders combined with a 4.10 rearend and a NV4500. My truck weighs around 6300 lbs with a full tank of diesel and driver. In town my milage sucks, (15-16). On a recent trip on the highway we kept very close tabs on the fuel consumption. With around 800lbs in the box I got close to 24 mpg. (Imperial) I kept engine speed in between 1,600 and 1,800 rpms which worked out to between 60-65 mph. This is significantly better than with the stock size tires.

w6bauer

12-09-2008, 21:48

I would like to see a manual lockout hub made for the K series vehicles. I feel like this would help mpgs

Robyn

12-10-2008, 07:33

The very small amount of stuff thats moving when the rig is not in 4x4 is so small that I doubt you would see any difference outside of a high tech lab.

The front end is disengaged by an actuator so the gear set and the front drive shaft are stopped under normal conditions.

The design of the front end (IFS) is not one I am impressed with but they seem to last fairly well when not subjected to nasty poundings.
The axle design is not readily adaptable to a "Locking hub" design.

Best

Robyn

JohnC

12-10-2008, 12:08

Interesting. I don't think it'd help mileage much, but I've had 2 of these puppies wear the carrier in the area of the left side gear to the point where the stub axle moved around so much it couldn't seal any longer. A disconnect on both sides would stop the mad spinning of the side gears and spider gears...

Robyn

12-13-2008, 08:53

I have always had little love for this design because of these factors.

The engineers must have been pressured from higher management to make this quicky solution.

The whole design is just dripping with the telltale signs of "Shortcuts"

The cheezy single bearing on the wheel end of the axle stub. The thermal actuator and of course the issue spoken of with the disconnect and spider gears.

Fords articulated rendition of the straight axle was another abortion.

My feeling is this, if someone just can't deal with a truck, then buy a car and be done with it.

I have put a couple million miles in behind the wheel of a 4x4 of one type or another with a straight axle up front and never found these to be objectionable.

Never once did I find myself annoyed at having to get out and turn the hubs in.

All the old stuff just worked and the mileage was as good as it could be.

Little 82 K Blazer with a 6.2 that got 24 MPG hwy.

OMG what were they thinking. ALL the complexity and extra parts and goodies that wear out and need service.
And to top it off the mileage went right in the toilet too.

The later trucks are what they are and I dont think there is really much that can be done to improve the mileage a whole lot.

A 2500 K Burb (IFS) with 6.5 can do around 20 MPG give or take a bit when things are right and driven accordingly.

best

Robyn

tank140

09-02-2009, 08:38

hi all

I get about 30 mpg from my Landrover Defender 6.5 TD on the high way over here in the uk
I think that is great as some of my buddys ony get about 20mpg from there late defenders

cheers
tank

http://i21.photobucket.com/albums/b264/tank110/140aug20062.jpg

Robyn

09-03-2009, 08:00

30 is a good number :D

The size and weight of the rig makes the difference for sure.

Lookin good

Robyn

93GMCSierra

09-03-2009, 11:04

tank140

09-07-2009, 05:11

Hi mate

That is UK Gallon 1UK gal = 1.2 US gal so that would make about 36 us mile / gal

not bad for a for a 2.5 tonne truck i think:D

tank:cool:

DmaxMaverick

09-07-2009, 07:56

Hi mate

That is UK Gallon 1UK gal = 1.2 US gal so that would make about 36 us mile / gal

not bad for a for a 2.5 tonne truck i think:D

tank:cool:

Actually, it's about 25 MPG/US (30 x .8327 = 24.981). Still, not bad for a 2.5 tonne truck. 36 does sound better, though.

BigDiesel

09-10-2009, 13:02

I was reading once over on the TDR(love my cummins:D) that the efficiency was best served not at a certain amount of boost, speed, or rpm's, but rather by driving with the pyro @ 600 degrees. Apparently some studies have proved that diesel engines are most thermally efficient at that temp. Now if one could combine 60 mph, 1800rpm, and 600* on the pyro...

moondoggie

09-14-2009, 07:45

Good Day!

Interesting! It would be quite simple to drive the Wastegate Actuator Solenoid with a closed-loop servo controller, to control the wastegate of a 94-on truck at whatever temp you would like. This actually came up a number of years ago, but never went anywhere. You'd probably want to terminate the Solenoid wires with a resistor, & would certainly have to have at least a boost fooler, so the PCM would think the boost was staying in an acceptable range.

I sure wish I could have pursued this, but never had the time. It sure would have been fun... :(

Of course, none of this applies to me now. I'm bailing on my two 95s, having just bought a 93, which of course doesn't have PCM-control for the wastegate. That's in fact one of the reasons I went backwards to a 93 - there's only two wires to the IP.

Blessings!

stezloco

02-29-2012, 16:57

i'm supposing the choice of stock pistons over 18 to 1's is because were not chasing power but efficiency...higher c.r = better volumetric efficiency and therefore better burn equates eventually to better mpg....
you cant have power and economy...you have to make a choice or compromise with shi##y mileage.acceleration up to speed is a big user of fuel because we all get up to speed at a different rate. i doubt i'll ever see 20 mpg in this truck despite being on imperial gallons.if we could 'knock off' half the cylinders electronically (compression and fuel delivery)when at cruising speeds you might see better figures but this engine just cant do that.i got the best mpgs out of my truck the day i bought it and drove it home with a badly split vac pipe, had no problems other than the odd puff of black smoke but since i fixed it and i'm getting a closed wastegate and normal boost conditions, i havent seen those kind of figures since. maybe welding shut the factory wastegate and bolting on a massive wastegate/shunt pipe would get your preturbo backpressure/temps down and allow you to run with it wide open so no boost ...or am i barking up the wrong tree here ......?

phantom309

03-03-2012, 12:13

i suggestedthe same thing long time back, got laughed at,.
i proposed a solenoid with a switch that dumped the boost at cruise throttle position, dropping drive pressure to zero and switched back to full boost when needed for power,.

There is now the school of thought that the different turbo's available and being used on the 6.5 will get up to 2mpg better fuel mileage because the drive pressures are lower than a GM turbo,.

Nick

stezloco

03-05-2012, 12:46

DmaxMaverick

03-05-2012, 17:15

If the boost sensor doesnt see any boost figures then wont the fuel programming 'ride' on a different part of the fuel 'map' and not follow max boost/max power part of the map? unless its designed to put the fuel in anyway to hell if youve got the boost or not ,hence the black smoke..i suppose i'll have to try this 'boost dump' out for myself to see if theres any logic to this logic .i wonder if the programming produced by the chip tuners could use this to gain some extra mpg's in the cruising rpm range depending on your gearing/load with zero boost showing.would be interesting to find out...everybody seems to be chasing max power most of the time.
if the standard turbo's still produces some boost even with the wastegate fully open , as ive read on here,then surely the wastegate isnt big enough for this particular application but big enough by design to retain some boost/turbo speed so it comes back on song when you stab the throttle.
i'm supposing the original design remit was to find the middle ground but i think the 6.5n/a engines do better on fuel because their map is centred around their breathing without a turbo and thereby dont need the 'extra fuel' so naturally run better mpg's...
If by chance Mr Kennedy is reading this drivel,and if by chance he decided to experiment by overlaying 2 or more chips into a switching unit attached to the dash.... I'd definitely buy into this..i'd love power on demand and economy 99% of the time..isnt this what the newer tech programmers do anyway?....is it worth investing any time/effort into this Mr K? or am i just dreaming one step too far ?? you could call it a K-DOG programmer (or something else) you must have a few standard chips laying about doing nothing to try it out??? standard , mild tune with boost dump,tow tune and max power...??? just a daft thought

Sounds good, but no. Combustion gasses drive the turbine. The gasses come from fuel. More fuel = more drive pressure. More drive pressure = more boost. Not the other way around. Late model high-tech Diesels, such as the Duramax, have a MAF active in the fuel mapping. They are able to "limit" initial fuel volume, and increase it as MAF sensed air volume increases. The EFI 6.5L doesn't do this. The fuel you get is "mapped" according to throttle position and RPM, in a static model. This is why black smoke is the result of too little air (boost) for whatever reason. They smoke because there is too much fuel for the O2 available.

N/A 6.5L's get better mileage, mostly in part, due to its lack of baggage. The turbo on TD engines causes a significant amount of parasitic loss in the inlet/outlet path. It takes additional fuel to overcome the loss, thus lower mileage. All else equal, more power or more economy....Pick one.

Now, on the lines of improving cruise mileage, I've often thought of a "bypass" system the would essentially make a TD engine N/A when more power isn't needed. This would require a compressor bypass, and an "open wastegate" ability. Easier on a Duramax LB7, because it has active MAF sensing, preventing excess fuel at higher throttle positions. Maybe I'll put it to the test sometime.

JohnC

03-05-2012, 20:39

I've often thought of a "bypass" system the would essentially make a TD engine N/A when more power isn't needed.

Can you say "Turbo Lag"? ;)

DmaxMaverick

03-05-2012, 20:58

Can you say "Turbo Lag"? ;)

Actually, that could be a thing of the past. With a bypass, you'd get full N/A intake air off idle, and about the RPM the boost would normally spool (the engine speed, not the normal lag time), the turbine could be nearly wound up. Close the bypass, and instant boost. With wastegate closed, you'd still have the exhaust gas restriction of the turbine, but I think that's better than a restriction at both ends. It would take some refinement to smooth it out, but I think it could work.

stezloco

03-06-2012, 09:53

:DI think weve just come up with a brilliant new invention ...should we call it a SUPERCHARGER ?.... its catchy .....he he

stezloco

03-06-2012, 11:17

Going by what youve already said about the fuelling being fixed and dictated by a 2 d map ie throttle position and rpm (but with no facility to measure load) you'd still need a suitable map to carry out the mod to reduce the fuelling at cruising speed whilst bypassing the turbo altogether..and you'd be stuck with just that ..1 map, unless some clever so and so takes up the crazy idea of layering chips which are switchable between normal /towing/cruising with bypass/max power..thats 4 layers.....essentially a programmer??
' is this even possible Mr Scott?'
'aye Cap'n but I'll have to check with Mr Spock first'
you'd need 2 very good sealing butterfly valves , one in a seperate intake branch to open up to a k+n say...and another to open up the 'bypass' loop in the exhaust...? thats totally do-able but I'm dead stop at the multi layer chip thing.
any more crazy thoughts???
To the Bat-cave......

JohnC

03-06-2012, 20:05

I guess I thought you were bypassing the turbine, since that's just as restrictive...

DmaxMaverick

03-06-2012, 22:18

Yes, initially. It would have to be brought online eventually, shortly before more power is needed. With exhaust gasses already flowing, the turbine should spool up very quickly, like a brake stand. If all you are doing is tooling around and more power isn't needed, of course the WG would remain open. It would have to be in concert with the intake bypass. An unrestrained compressor will cause overspeed of the turbo, with the turbine engaged. I think the key will be either a throttle position limit while in "low power" mode on older models, or the MAF could manage that on later models. It's a rough idea, but I think it could work. The question is, will it be practical? I doubt there will be a ROI. Maybe.... Or just for fun.

stezloco

03-07-2012, 10:17

quote:
The EFI 6.5L doesn't do this. The fuel you get is "mapped" according to throttle position and RPM, in a static model. This is why black smoke is the result of too little air (boost) for whatever reason. They smoke because there is too much fuel for the O2 available.

Now, on the lines of improving cruise mileage, I've often thought of a "bypass" system the would essentially make a TD engine N/A when more power isn't needed. This would require a compressor bypass, and an "open wastegate" ability.
unquote
So how would you deal with the fuel being delivered without boost with your bypass fitted? sounds great by the way ,ive already built one in my head.
just the fuelling to sort out now then?
i'm wondering since the chips are a plug in item anyway, why not jack one in beside the master with multiple switches for each connection and switch them all over before you turn on the ignition so no voltage on/off spikes, then you'd have 2 available maps , one could be a N/ASP map ,as you'd need for your bypass conversion, the other a power map of your choice....? why wouldnt that work, its not rocket surgery ,just a matter of experimentation and a spare N/ASP chip???? ISNT IT????

More Power

03-14-2012, 11:50

I drove a 3.42 geared NA 6.2L (1500-series 4x4 pickup) for several years. With a 700R4 automatic and driven for fuel economy at 65-mph it would routinely deliver 23-24 mpg.

I eventually installed a Banks turbo kit. It was very difficult to keep the speed down and not "use" the turbo, but when I did drive it for fuel economy, it only decreased about 1-mpg to 22-23 mpg. So, not a big difference, if I could force myself to drive for fuel economy.

The Banks turbo was the non-wastegated variety, which was pretty free-flowing. That turbo required about 2500-rpm and a fair amount of throttle to spool it to 7-10-psi boost pressure. At a 65-mph unloaded cruise on level highways (about 1800-rpm), the turbo produced no or virtually no boost. Turbine drive pressure was pretty low.

Rather than swap chips/programs, installing a larger, more free-flowing turbo might accomplish more, easier.

Jim

convert2diesel

03-14-2012, 14:42

Just throwing out an idea. Back when Ford first installed a turbo on their Binder Engine, it did not meet California regs, specifically on transition emissions. To meet the regs, Ford installed an aneroid in the dome of the DB2 that essentially restricted rack travel until upper deck pressure exceeded a certain level. This makes sense as very little throttle movement is required to make the DB2 go full rack.

If one was to combine this aneroid with a two position wastegate actuator we could theoretically have an engine that could operate at part rack (lower fuel flow) and only allow the turbo to spool to .5 to 1 lb of upper deck pressure (pick up some VE) and when needed, transition back to full wastgate control and full rack travel for power.

This could all be controlled manually with a couple of electrically actuated vacuum relays, controlled by a switch on the dash, or driven through an older TPS switch that was used on the older 400 equipped 6.2.

That should produce NA or better economy due to maintaining slightly positive upperdeck pressure but with restricted fuel flow but still give you full power when and if it's needed. This method would work even better on the center mounted turbo engines (much lower exhaust restriction) and a 4911 pump.

Just a thought.

Bill

stezloco

03-15-2012, 02:43

Thanks Jim,
on larger turbo's ...
i bought an HX35W from the USA from an ozzy bloke who screwed me by sending it over in bits (! ? ! ? ! ) ultimately damaging the compressor wheel and bending the shaft slightly on the journey thro' sh#t packaging (i think that was the intent from the start)...dont get me started on that one..I still rage about it, i ended up buying a recon centre section for the same money again so i'm into this thing now for a lump i'd never get back if i sold it.
I was going to fit this but was put off by the articles i read about pushing the power band further up the rev range thereby defeating my primary aim, to get more mpg out of this truck if at all possible.It actually has more than enough power to pull as it is (I'm used to weedier jap trucks and Landrovers tho') I should give myself a firm kick, I said i wasnt going to spend this money, but I have. I'd need a power chip/g/box shift-point change to match this turbo's character. for all the info ive read about chips and turbos, i dont recall if theres info about a chip combined with an HX35W,and the results,( my memorys letting me down here,)??? any ideas,is there???
If, as has been said, the 2d mapping puts the fuel in anyway, then i'm going to be missing the air to burn the fuel and will run dirtier, still not achieving the objective. I still like the idea of 1 chip for economy, the other for Max power/towing ability.I pulled my own chip yesterday out of curiosity mainly to record the no's and have a look at the connections with a view to doing what ive already suggested, i see no technical reason why this cannot be done and wonder if the gains would weigh up against the cost of a 'heart bypass' so to speak.would need to get hold of an 'F' code non-turbo chip/or ECM, if there is such a thing. If anybody reading this can tell me any possible pitfalls with the idea , i'm all ears.
your decent mpg's were probably down to the combination of setup you had on that engine, i.e. lighter truck,gearing, small precups, mech pump, high power band in the rev range (did you up the fuel @ the pump or leave as standard to better burn what was there/run cleaner??)
I'm stalled as to where to go with this one, or not at all.It'll still take £££'s to complete it, i'm halfway there i suppose.
still might get a chip (who's chip tho'??)if i get the right advice from somebody else's experience with the same truck.(always preferred)
I have the lead/GMtech programme from Engh Motors on a netbook i keep specifically for the task and wondered whether to buy his chip or not but had no data from him or reports from anybody using his chip, so i put off. Mr Kennedy says 60 hp is the realistic figure anyway ,and thats roughly what they claim.Is there a way of checking my chip no's to see if it has been changed already ??? how would i know?
recently bought a set of 4 hummer H2 wheels/tyres 315's x17...fun trying to get these to clear the fronts, fitted straight onto the hubs (and were hubcentric!) looks as tho i could use a 3" lift now though, i have 2" wheel spacers on the rear to balance the look ...will be moving my bumper forward and cutting the lower spoiler and fill in panel as well...these taller tyres might get me a few more mpg, ...just need to look for that vssb thingy now...
fun n' games eh......

More Power

03-15-2012, 09:43

I actually talked to Gale Banks about his 6.2 turbo kit, and mentioned that the turbo didn't spool till about 2500-rpm and with quite a bit of throttle. I was expecting to see boost more of the time.

Gale's response was that "the power will be there when you need it."

Of course, he was right. My truck drove more or less just like it did without a turbo, and delivered almost identical fuel mileage in light load driving. But, the power was there to pull grades, pass or accelerate. It just took the turbo a couple seconds to spool before the power became available.

So... theoretically, reducing turbine drive pressure to look for more mpgs can be done by installing a larger turbo. But, you'll still have a turbo for those times when you need more power. As Gale said, "the power will be there when you need it."

Yes, I did "Turn up the Pump" during the Banks 6.2L turbo kit install. I don't believe that affected fuel economy. It takes a certain amount of fuel to move a vehicle down the highway, no matter whether turbo'ed or not, no matter where the fuel rate screw is set to. The maximum fuel rate was increased, which means fuel economy would be affected only when using the additional fuel. The delivered fuel rate during normal light load driving shouldn't change.

Jim

dragonriot

03-18-2013, 23:14

So this thread was necro'd about a year ago, but after reading everything I thought I would chime in with my situation as well.

My truck is very stock on the outside... no Chicken Lights, stock mirrors, no bug shield, and nothing else that would increase the Aerodrag on the truck. I have fairly large tires, about 32x10x16.5 in US measurements, and hardly ever tow anything larger than a 150lb boat on a Sunfish Trailer. (speaking of which, I need a new sunfish trailer, if anyone has one laying around) My mods include a Turbo-Master set to Heath Specs, a performance chip from Heath Diesel, newer glowplugs, new PMD on a FSDCooler, removed Air Intake Ring, and don't have anything blocking the radiator or bumper holes in the winter (though I know I should.)

At 65mph in Overdrive, I'm running at ~1950RPM, and in Summer I get about 21mpg highway and 18 in the city. In Winter, with Primrose Winter Power fuel additive, the best I've seen is 17MPG on the highway and 15 in the city. I don't know my final gear ratio, but I think it calculates out to about a 3.42 rear end, as I got a 3.10 calculation from my Overdrive RPM. When I checked it without overdrive, I was hitting about 2400RPM at 65 in third gear, and it just didn't sound very nice so I have only run that way once for the purpose of testing.

I would like to get up to 24mpg without spending a crapton of money on the mods, as the truck already has 221,000 miles on it. I still have thoughts of doing a Cummins 4BT swap eventually for the magical 35MPH they are advertised to get in these trucks, but I'm pretty sure it would be cheaper in the long run - even with increased repair costs - to buy an older mercedes 300D or VW TDI when my engine decides to go the way of the dodo. I know that's blasphemous to say in here... but our trucks are becoming more rare, and harder to find parts and replace big ticket items.

DennisG01

03-22-2013, 10:49

Drag, have you adjusted the VSSB for the slightly larger tire size? I think what you have is about equal to 265/75/16?

For a few years now, I've been toying with the idea of adding a front "skirt" under the bumper. Kind of like a big air dam. I was thinking of making to within 6" of the ground. Maybe use some steel L-channel bolted to the underside of the bumper, then plywood for the vertical section - but it would need to be braced so it didn't just fold in on itself at speed. I haven't looked at it any further than that, though. Wanna give it a go?:)

DennisG01

03-22-2013, 14:21

Drag, I think your tire size is about equivalent to my 265/75/16's (stock is 245) but I don't get MPG near that - but I suppose part of that is because of the larger vehicle and whether or not you have the larger rear end and 8-bolts. Have you adjusted your VSSB (or whatever a '94 has) for tires? Otherwise, your speedo and odometer aren't reading correct.

If you jack up one wheel... make a mark on the driveshaft and rotate the tire once. Count how many times the driveshaft rotates. ~ 3-1/2 would give you the 3.42, ~3-3/4 would make it a 3.73.

Or, as long as a PO hasn't changed it, just look at the RPO code list in the glovebox. GU6=3.42 and GT4=3.73.

OK, on to the more interesting stuff...

For quite a few years I've thought about adding a large air dam under the front bumper. It wouldn't be pretty, but it would at least give me an idea if it works. My thought was to use some 1-1/2" or 2" L-channel mounted to the bottom of the bumper, and then attach plywood to the vertical section of the L-channel. Extend the plywood to within about 6" of the ground. Add some support rods from the plywood to the undercarriage so the thing doesn't blow away at speed.

That's about as far as I've gone, though - more just theory than anything else. Wanna give it a go and see what happens?:)

arveetek

04-01-2013, 15:03

I just returned from an 800+ mile trip, and pulled down the best MPG to date with my 95 Tahoe.

Averaging 68 mph on the freeway I hit 18.67 MPG. Normally I average closer to 17.5 MPG. I've never really taken any long trips with this vehicle without some sort of trailer or heavy gear, so I've never really got to see what she'd do solo.

Also, take into consideration that the old Tahoe was loaded down with three passengers and lots of luggage; and she still did all this with over 264K on the clock! :D

We had actually planned to take my wife's minivan, but at the last minute, the engine started puking oil into the coolant. So now I get to see what I have to do with a Chrysler 3.3L with only 160K on her.

But old faithful was standing by ready to go and didn't let us down!

Casey

Robyn

05-15-2013, 07:55

Your Tahoe is very similar in size to a K5 Blazer and they would do 25 mpg hwy with the 6.2 n/a engine.

The 6.5 td has never been a miser on fuel.

Our 94 Burb got 20 mpg once on a trip, but usually it get 17

Missy

greatwhite

06-16-2013, 04:58

TDSECK

06-17-2013, 12:38

I just had my 4:10 ratio axle replaced with 3:42 after much reading and thought about it. I also had the factory posi replaced with an Eton unit.

Thanksgiving of 2011 I towed my old 91 Montero 4x4 to Maine on a U Haul trailer and got around 15 mpg from NJ. I didn’t go past 55 mph for the trip.
On the trip home I got 18 mpg but had to keep the speed under 60 mph as I didn’t want to go past 2000 rpm for my 6.5. It was tuff having every one pass me for the whole trip home! So it was bitter sweet, good mpg but a very slow drive.

This Sub was very well taken care of by the pervious owner. It has 1149000 miles on the clock and runs and starts well.
The only mod I can see is the FSD has been replaced and relocated in the front bumper. Also the exhaust system is 4”. I replaced the straight through type muffler with a 4” reveres flow muff to lower the noise level inside.

I am planning another trip to Maine in July and will let you know what mpg I get with the new gearing.

So far I like the 3:42 gearing MUCH better than the 4:10
I have no plans to do any heavy hauling with my Burb. I bought it for long trips and hauling big stuff inside with the 3rd seat removed. (a 4x8 sheet of dry wall or plywood fits right in!
So far:
Less engine and exhaust noise (no one talks about that)
Less engine wear per mile
Hopefully better mpg

Some one said the having 3:42 gearing makes your truck or Sub a dog! I disagree! It’s a diesel and now the rpm’s are 1200 to 1500 for everyday driving around my NJ suburbs right where it should be, in my opinion.

The Trany Shop offered to recalibrate the vehicle speed sensor buffer but I felt I could do it after reading about it in the Vol 1 Book about the 6.5.
Has any one out there done that mod them selves and or installed the 7-position dip switch instead of the jumper settings?

PS: FYI I wanted to install a overdrive unit but found out from the mfg that the “Auto” type transfer case that is in my Burb is a one piece unit and can not be split apart for the install, other wise I would have gone with the overdrive unit…
The manual transfer case will work with the overdrive unit I looked at.

DennisG01

06-22-2013, 11:38

VSSB re-cal... yes, have done it. I bought a DIP switch (after I did the recal) with the anticipation of soldering it in for future use but never did. Either way, it's a pretty easy-peasy thing.

TDSECK

06-25-2013, 10:49

Can you tell me where you bought the dip switch?
Radio Shack no longer sells the one shown in the Article written in the Turbo Diesel Vol 1 Page 51
Also I can not fig out how you translate the divide code into ones and zeros.

greatwhite

08-31-2013, 14:09

1998 K2500, ECLB, Auto, 4:10, 265 75 16.

Latest results are 18 MPG combined.

Combined is roughly 60% highway, 40% city. Highway speeds not above 100 Kph, windows up, AC on.

Just switched rims to a set of PY0's from a later 2500HD. Requires far less throttle for same rate of acceleration and lighter touch highway to maintain speed.

Weights:
steel wheels scaled at 34 lbs each
PY0's scaled at 17 lbs each

That's 50% savings at each wheel in rolling mass.

Hoping for a small return on the less rolling mass. Would be overjoyed with even 1 mpg increase.

DieselDavy

09-16-2013, 06:28

Wow!
While 68 lbs are a lot go haul down the road, I'd be surprised if you gained 1 mpg.
Keep us updated on how much you gain!

More Power

05-25-2022, 13:06

ToddMeister

05-26-2022, 07:53

Yeah my 1995 with a CKO-HX40W-II turbo, DS4, and 4L80-E is very similar in MPG to your 94

Most of my miles are local stop/go in town and I am averaging about 15 MPG

More Power

05-26-2022, 08:16

Yeah my 1995 with a CKO-HX40W-II turbo, DS4, and 4L80-E is very similar in MPG to your 94

Most of my miles are local stop/go in town and I am averaging about 15 MPG

The Blazer produces 15-16 locally as well. Doesn't make sense when compared to that GMC I owned with a Banks 6.2L. The Blazer's engine is equipped with the small port cylinder heads, which don't seem to make a lot of difference - or there are other factors that make more of a difference.

Our 6.5TD Power Project engine ran with the large port cylinder heads, 4L80-E, 4.10 gearing, GM-8 factory turbo, a mechanical DB2 marine pump and matching injectors. It would deliver about 2-mpg better than the 1994 Blazer (we owned them together in 2000).

So... it looks like the transmission and the turbo make up the rest of the difference in MPG. I do know that when I swapped in the OD equipped TH700R4 for the TH350 3-speed non-OD automatic that that 6.2L GMC diesel K1500 pickup had in it, I saw a jump in fuel economy of 5-7 mpg before the Banks system was installed. Adding the Banks Sidewinder made no difference I could measure in the 65-mph fuel economy (50 miles per day commuting speeds).

Robyn

05-28-2022, 14:44

Just my opinion here...

Having been into several 700R4 OR Currently called the 4L60E

The 700R is a wimpy gear box.....Even the later renditions are nothing to write home to momma about.

I have opened up several of these that were behind 6.2 diesels....Literally shook to pieces.
The clutches are tiny, the sprags are also tiny.

The planetary gear sets are small....a 5 planet upgrade helps....

The factory sun shell is a POS..."The beast" (After market unit) is much better

The input shaft is pressed into the aluminum clutch housing.
The housings break or the splines rip out.
There is a hardened steel piece the presses over the aluminum hub to help it out.

Several other issues.....
The 700R or 4L60 is OK behind the V6 and the 305 V8.....

The factory did not use the 700R / 4L60 behind the 6.5 for a good reason....The N/A 6.2 could break them....The 4L80E is a good durable box and will hold the 6.5....

The cost of doing the swap, plus all the parts that need to be massaged....Drive shafts and such....

IMHO This swap would be a really bad jump.....And I am not sure you will get much if any gains that will ever pay off before the little gear box that could ...grenades...

When the 700R goes bang....It's very ugly, and usually spreads parts all over the street.
I trashed 3 of the 700R in my K5 Blazer......Then dropped in a TH400 with a nice tight RV coverter.....No more issues

The 4L80 does have a tad more parasitic drag due to it's size....Size ....as far as bigger parts is a good thing.
The TH400 and the 4L80 share some internal parts....Bigger is better..

Ma general likely knew what they were doing....

Just sayin....

2INSANE

05-29-2022, 20:07

I've been thinking lately about the questions posed here for improving fuel economy in the 6.5.

My thinking includes a trans swap to a TH700R4 which is more efficient (higher OD and less rotational resistance) than the 4L80-E, a mechanical DB2 (possibly a 6.2L pump) and a Holset HX-35 for a more free flowing turbo.

I know that that combo in a 6.2L diesel pickup I owned in the 1990s delivered 24-25 mpg. That truck was geared 3.42, and ran a Banks Sidewinder turbo system. The 6.2L engine itself, DB2 fuel injection pump and matching injectors were all pretty fresh.

By comparison, the 1994 Blazer we have (6.5TD/4L80-E, DS4 and 3.73 gearing) has to be coaxed to produce 17 highway...

Just thinking out loud...

After doing my 700r4 swap behind the 6.5 TD Optimizer with 4.56 gears, GM1 turbo (Soon HX35w), it for sure gets better MPG in town and on Hwy compared to the Th400. Even better Mpg in town then my Stock LBZ Duramax. I have not crunched all the number yet except Hwy mountain grades where it gets about 15mpg empty at 75mph and about 10mpg towing a heavy 2200 pound pop up camper. I have not been conservative. So far 3,000 miles with the built 700r4 and it is still going strong with my heavy lead foot! That 1st low gear is amazing!

More Power

05-31-2022, 11:08

I put 40K on a "diesel built" TH700R4 behind my 6.2L Banks turbo. No problems. I know that the 4L80-E is more robust, being an evolutionary advancement beyond the TH400 3-speed non-OD.

A fellow east coast member came to a couple of our first Rendezvous here in Montana. He drove a late 1980's 1500 Suburban powered by a Banks turbocharged 6.2L diesel. That Suburban had a TH700R4, and he towed a 36' triple axle Airstream all over the country.

We've produced two different articles on building a reliable 700 for the 6.2/6.5. Gotta use the right parts... use the right TC and do it all with the right case.

Robyn

06-02-2022, 16:25

Towing a big trailer is a scary thought with a 700 R handling the gears..
Yeah...I am very much down on the 700R
After breaking several in the 80's/90's it soured me.

Then being into them with bunches of hands on reinforced my dislike....

YES....RIGHT PARTS, TOP NOTCH SHIFT KIT (SET ON KILL)

A top notch converter with furnace brazed fins on the Turbine, pump and stator.
Better sprag in the stator....A much better converter clutch.

The converter is small in these and with the clutch in there it takes up space that needs to be used for pump and turbine.

An oil pump with more vanes in the rotor.......More oil volume available.

Big azz cooler out front

Transgo Dash2 shift kit installed on the stoutest settings.

The Input shaft reinforcing sleeve on the drum.....

5 planet carriers....The beast sun shell....Super duty 2-4 band.
Corvette servo......

A few other goodies.....The late units with the late style case (4L60E) with the tow haul option.....This will really help when working it hard.

One thing to remember....These boxes have a nasty little thing they do....

THE 2-3 and 3-2 SHIFT CLUNK (Light to mid throttle)

The 2-4 band has to be released....and the 3-4 clutch applied to make 3rd gear....

During the shift the output shaft goes into a reverse torque condition when the band is released and then the 3-4 clutch is applied.

The slack in the drive train (Especially the 4x4 rigs) is all taken up CLUNK....Very annoying and will scare the hell out of the unknowing owner....

Another thing

The T case in your Blazer/Tahoe has a 32 spline input shaft at the coupler with the tranny.

The 4l60 uses a 27 spline....Either swap the shaft or scare up a different T case...

The T case adapter is different too....Not sure about the frame cross member and rear mount.

Drive shafts will be different length due to the different tranny.

All doable.

The ECM PCM will likely need some massaging.
Not sure about the wiring harness that connects to the tranny.....I think these are different too.

Scaring up a similar year rig with a 5.7 gasser for a parts goat....might be a good ideal...
Somebody offers a kit to do this swap....

A bunch tougher than in the old days.....Build the gear box, bolt it in and swap drive shafts...Good to go

Probably have to massage the T CASE shifter too.....

The 700R converter has a smaller bolt pattern...The 4l80 has the large pattern.

Most 6.5 flex plates have 6 bolts.

Since the 6.5 never had a 700R the holes may need to be added to allow the small converter to bolt up.

Fun stuff.....

More Power

06-06-2022, 10:21

... clip...

Probably have to massage the T CASE shifter too.....

The 700R converter has a smaller bolt pattern...The 4l80 has the large pattern.

Most 6.5 flex plates have 6 bolts.

Since the 6.5 never had a 700R the holes may need to be added to allow the small converter to bolt up.

Fun stuff.....

The swap from a 700 to a 350 was so popular back in the 1980's that the aftermarket made a trans/txcase adapter just for that swap, that made it really easy. The adapter allowed joining the TH350 to the original transfer case used behind the 6.2. Didn't have to change the position of the transfer case or cross-member.

Swapping to a 350 during the 1980's didn't have a lot of downsides - mostly upsides... The national speed limit, even on Interstates at that time was a snail's pace 55-mph. I swapped back to a 700 when the national 55-mph speed limit was lifted. The TH350 made the 6.2 unusable for anything other than back roads... because 70-mph meant 3000-rpm in a 4.10 geared truck. Our speed limits were even higher - they are 80-mph now. The TH700R4 had a 0.71 OD. In my 3.42 geared truck, that TH700R4 OD produced about 1800-rpm at 65-mph, which was heavenly after 200,000 miles of having no overdrive.

Another big advantage of the OD was that the diesel rattle practically disappeared at 65-mph and over. Then, there was the fuel economy advantage... I saw a change from 17 to 24-mpg during my 50-mile commute. All combined, I was very happy with the TH700R4.

Going to a 4L80-E in a non-computerized truck means buying a computer and wiring harness (about $1200) in addition to the cost of the transmission. It also means engine sensors (TPS - ESS). I installed a 4L80-E and computer and wiring harness and engine sensors in a non-computerized truck. I did it for the power handling capability.

Someday, if the DS4 or existing 4L80-E in Sarah's Blazer ever give up, I'll be highly temped to swap in a TH700R4 and mechanical DB2. There's no reason this engine can't deliver low to mid 20's in fuel economy instead of the 15-17 it does now.

There are two flexplate options for the 6.2/6.5 - "light duty" and "heavy duty". The only difference is TC bolt circle - both use 6 bolt TCs. The TH350 and TH700R4 share the same smaller bolt circle, and the TH400 and 4L80-E share the same tiny bit larger bolt circle. The difference isn't very much. From a short distance away, I doubt many could tell the difference in size between a pair of TCs or flexplates made for each transmission.

Here's a pic of Howard's 1987 1500 Suburban and his 36' Airstream... There's a TH700R4 in that Banks 6.2 powered Suburban. He was from New Jersey. That pic was taken here in western Montana.

Robyn

06-07-2022, 05:52

That Airstream is no lightweight.....I am very surprised he was able to keep the little 700R alive and kicking.....

Yeah.
The good old days... when life was a simple bolt in option to make just about anything fit anything else....

Yes
The small bolt pattern flex plate and the large pattern.....The 6.2 with the 700R (Or TH350) got those and the 6.2/6.5 with the TH400 OR 4L80 had the large 6 bolt plate.....

If you go to the DB2 Pump and a hydraulically controlled 700R/4L60 Then the electronics really means ZIP......It will all work fine.....

Trying to get everything to run with the DS4 becomes an issue when you start swapping goodies.

Not impossible...but annoying at times....