Mileage

[nape]

I would like to know what I can do to increase my fuel mileage. I have several 6.2 vehicles with different set ups. All have 700r4 trans but anywhere from 456, 410, 373 and 308 gears. My main vehicle is a 90 model half ton Sub. I have an ATS turbo and 3 inch exhaust. I changed the intake to a J intake and am wondering if this helped or hurt. I am interested in power but especially mileage and am on a limited budget. What has worked for others and is doable in the garage? Thanks Nape

[farmerherb]

What kind of mileage are you getting now? I get 25 in my conversion van with 3.08 rear, no turbo.

[nape]

I get 16 to 18 on the highway depending on the speed I drive. I had an old Sub. with the red engine that regularly got 25. The turbo helped with the power but hurt the mileage except for towing. It will now tow a 6000 pound vehicle on a dolly in overdrive with the TC locked and maintain pretty good speed in MS. I think I have increased the chamber that has to be pressurized by going to a J intake and that may have hurt performance. Wayne

[TimK]

Getting 16 to 18 mpg for a full size suburban is in the range of normal. If you consider the same sub with a gas engine you would probably be getting half that mileage. The lowest cost items would be to make sure the truck is tuned, timed and heathly.

TimK

[catmandoo]

on my 94 3/4 2wd td sub with 4:10 i get right at 20 mpg at 55 if i get up over 60 it drops to about 18 or so,now my 94 1/2 4x4 gasser with 3:42 will pull right at 18mpg across nebraska doing 75.i think if i put so 3:42's in the 3/4 it should get me up in the 20's easy at 75.

[moondoggie]

Good Day!

[john8662]

nape,

I don't think you hurt anything by adding the J intake, if anything you got the engine to burn cleaner by removing the EGR stuff, and less restrictions. On a turbo engine, restrictions are not as important as with naturally aspirated, but you didn't hurt anything. I doubt you would see any "seat-of-your-pants" improvement though.

Is your suburban a 4x4? migh check to see if your auto hubs are unlocking. The 4x4 burbs and trucks don't usually see that great of mileage, usually 2mpg worse in all cases compared to a 2wd. What is the 90 model sub geared?

[nape]

My Sub is a 90 with a Crate engine from Chev. The engine has around 125 thousand miles. The engine has an ats turbo with 3 inch exhaust with a glass pack muffler, 255/70/15 tires. In MS you always run the air and I always drive fast. I think that at 65 or 70 it should deliver in the low 20's. I am not sure of the rear gears but they are in the 3.42 to 3.08 range. I wonder if injectors would make much of a difference and whether or not exhaust and intake mods would pay off. The ats system incorporates the stock intake. The intake muffler has been removed and a 5 inch dryer hose is routed to the intake. I changed from smog intake to J intake and this may have changed the turbo functioning but seems like it would only change the time taken to pressure up. I have to do something about this mileage. I have plenty of engines to work with. I have four running engines and three not running. I have three core 6.5 engines and am interested in building something for mileage. I would really like to see a build up with mileage/power in that orientation as the purpose. Thanks for all ideas. Nape

90 6.2 Sub with ATS turbo 700r, 87 3/4 Sub 6.2/700R4/410, 83 Sub. 6.2/700R4/410, 82 Sub. 6.2/700/342, 85 CUCV 6.2/400/456, 87 C30 6.2/400/488 and many many parts.

[moondoggie]

Good Day!

Oops, I forgot. We had an 84 Sub (6.2, 3.73 gears, 700R4, 4X4). It got 21 or 22 mpg in my commute (described in my last post). It dropped way down with a really small, low camper behind it.

I'd be DEEPLY interested in what you come up with to increase fuel economy. It's why I started driving these things in the 1st place. Seeking high mpg puts us in a distinct minority on the Page - most of the folks here want More Power!

Blessings!

Brian Johnson, #5044

[john8662]

Originally posted by moondoggie:
Seeking high mpg puts us in a distinct minority on the Page - most of the folks here want More Power! I guess I am in the club of wanting great mileage and in the club of wanting more power, guess thats why I have my collection of diesels. Some for mileage, some for power and pulling, one for running though the mud and offroad, and a work truck, to later race.

[catmandoo]

thats why i drive diesels,milage,i put on 60,000+ miles a year so the less fuel i use the more money stays in my pocket,but as for having both i don't think it's possible,at least i haven't been there yet,my truck would run just over 27,then put my banks on it and dropped to 25 but man i think alot of it was my right foot seemed to have a nerve impulse pproblem and was always pushing down,the power increase was fantastic,but what i've found is if i keep the egt under 400 i can still push up to 27,i would really like to try getting boost right off idle,i think this could be the key to both

[john8662]

I would figure that the ATS turbo system would give fast boost off idle. I have both sitting on the shop floor, waiting for a clean up before I decide which route to go, Banks or ATS. The turbo's from both the ATS and the Banks kits have the same A/R ratio and the same turbo. The difference comes from the mounting of the turbo, and that the ATS turbo has a more restrictive exhaust side. I would think that the ATS turbo would spool faster, but would suck at high RPM, so good on fuel cruzing, not pulling a load at higher RPM. I know Banks used two exhaust housings for their turbo setup on the same turbo. One housing for a fast spool, and the other for pulling. This turbo is going on my MPG truck, so I am a little weary, which ever turbo I put on.

[catmandoo]

i have kinda wondered about the banks,i have one on my 82 3/4 2wd sub and one i just put on my 92 pickup and the one in the sub seems to boost quicker even though it's a small engine??and as i said you have to keep the egt's down or the milage is going out the window.

[Stage1]

A couple of questions on fuel mileage. What kind of mileage is good for rolling hills driving in a Blazer? Does up and down small hills effect mileage of the 6.2? It sure does in my 03' Duramax 3500. On flat level ground the mileage is outstanding, but to add extra fuel to get up the hill hurts it quite a bit. This is a much heavier truck then the Blazer ( project vehicle in the planning stage). Mid 80's Blazer w/6.2; considering addition of turbo?? Trans is a 4L80E; axles are planned to be 10 bolts ( lighter weight and less hp to turn); gear ratio is still being considered?
Second question is gear ratio related. For optimum fuel mileage in a Blazer what should the engine RPMs be for 55 to 65 MPH. Assume that optimum milage is a function of engine RPM and related engine load at that RPM? The Blazer currently has the origional 3:08s. It will also have A/C.
Thanks for your thoughts.
Les

[catmandoo]

for the hills your probably in and milage i'd probably jump up to 3:42 or 3:73,those 3:08's are really gonna be luggin up the hills and probably downshifting all the time.i had 3:08 in my 84 1/2 pickup and it was nothing to pull 25mpg all day but here in iowa it's fairly flat,but even at that at 55 it always sounded like it was lugging,but if i got it up to 62 where all my diesels seem to like to run it would drop the mpg down to 23,then i put a banks on it and to heck with the milage man did that truck get fun to drive in a hurry.

[jcomp]

My Blazer gets nearly the same mileage going up and down hills as it does driving on flat land, 18-20 MPG. I hardly ever use overdrive in the mountains and it doesn't really seem to affect my mileage.

Your ideal gear ratio will depend a lot on your tire size. I think I'll be a lot happier with a set of lower gears; 4.88 is what I'm currently planning on and I have 37" tires.

[Stage1]

Thanks for the information on mileage in hills. The tires I am thinking of could be around 34's wo/wife, and a little smaller w/her. Do not want to do to big of a lift, somewhere between 2 to 4 inches. The turbo sounds nice!
thanks again,
Les

[mdregister]

This thread prompted me to check. I have been recording gallons and miles for awhile.

pre-DSG gear set up: towing approx. 2000lb and freeway both equaled about 14 mpg

after DSG gears: towing approx. 2000lb =15-16 mpg

freeway and unloaded = 18.5mpg

I guess that is not too bad for a K20 with a three-speed auto and 3.73 gears

[nape]

I am interested in the DSG gears. That sounds like a win win mod. If timing is crucial then the gears must be the way to go. I have been playing with the speed and noticed on the last trip with controlled speed with about fifty miles at 45 and 50 on the Natchez trace and around 300 at 70 - 80 on the interstate I got 18 mpg. I think the gears improving the air intake and possibly better exhaust could give me a couple of miles to a gallon. Does anyone have an idea about guage mounting in a 90 model? I would like to mount a tach, manifold pressure and pyrometer somewhere that was both functional and didn't look goofy. I have also replaced my fan with an electric one of off a late model cougar with a v8. I have been gone for a week but thanks for all the information. Nape

[mdregister]

NAPE,
I highly recommend the DSG gears. They where easy enough to install, once I got over the apprehension of doing the job in the first place. I have a thread around here somewhere that describes my smoke pattern (lack of smoke) after the installation of the DSG gears and dynamic timing to near-milspec 4.25-4.5*BTDC.

[TimK]

Nape,

I have the same size truck, ratios and DSG gears like MDRegister has. I also get roughly the same mileage readings.

For gauges I got a 3 guage pod that sits on top of the dash and doesn't look to bad. It's a cheap piece of molded plastic but seams to do the job. I thought it was made by Auto Meter or Auto Guage. I bought mine through a local auto parts chain here on the west coast called Baxter Auto Parts.

TimK

[Craig M]

Our 83 Suburban C10 6.2, 700R4, 3.73 gears gets 22 mpg on long trips on freeway at 60/65 mph

[TimK]

I am guessing I could squeeze at least 3 - 4 more MPG with an overdrive. The sub I had before this one I currently drive was a 2wd 3/4Ton with the 700R4 and it averaged about 18-19 in the City and 22 MPG on long hiway runs.

I would like to place a Gear Vendor overdrive behind the TH400 I currenlty have but the pay back on the mileage difference is around a 120,000 miles. Since this is not my daily driver, it might take 6 years to see the payback. If I can't convince myself that the increased mileage is worth it, maybe I can convince myself it's a new toy for the truck that I can't live without. I'll have to see what my wife says. After all she was nice enough to allow me to cash in my vacation hours from last year to by the new 6.5L and turbo.

TimK

[moondoggie]

Good Day!

Your truck will get a lot quieter with the Gear Vendors - maybe that will help with the DA (domestic associate).

Blessings!

Brian Johnson, #5044

[nape]

I set this engine in with around 130,000 miles on it. It cranks ok and runs ok. I have to replace the glow plugs and that is going to be a major pain. I think I will install injectors while I am doing the job. What kind of injectors will give the best mileage/power? Or is there any choice in injectors? I have never put injectors in one of these engines but I have to remove the pass side fender and replace so I think that will be the time to do the job. What about the high pop injectors? Can a 6.2 pump handle that kind of pressure? What about intake or air cleaner mods? I would like to fab up some kind of ram air through a K/N type air cleaner. What do you think? Thanks nape