Max fuel economy?

[Chevrolet4x4s]

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

Here is the 73-74 grille after I redid it


and what I started with

Heres the step by step process
http://www.hotrodders.com/forum/repa...le-125972.html

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

[allformike]

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

[allformike]

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

[trbankii]

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

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

[allformike]

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

[veager]

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

[dieselcj8]

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

[Edahall]

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

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

Some things that I could do improve economy:
Super Tune engine using glow plugs.
http://www.ford-trucks.com/forums/59...he-engine.html

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

Aerodynamic mods such as front air dam and rear fender skirts

[Dieselmania]

Moondoggie:

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

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

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

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

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

MP:

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

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

Dan:

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

A belated Merry Christmas to all

Bill

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

[john8662]

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

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

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

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

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

J

[Edahall]

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

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

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

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

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

J

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

[abec]

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

[pologuy14]

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

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

[jMedia]

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

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

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

[Edahall]

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

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

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

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

[jMedia]

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

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

[Edahall]

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

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

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

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

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

[jMedia]

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

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

[Edahall]

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

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

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

[jMedia]

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

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