Max fuel economy?

[Edahall]

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

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

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

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

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

[jMedia]

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

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

[Edahall]

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

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

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

[jMedia]

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

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

[npauli]

Wow!

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

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

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

[millwrightjesse]

Im getting 25.3 MPG in my suburban

[T-1000]

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

[jMedia]

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

Thanks again!

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

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

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

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

[tomtaylor]

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

[Vin82k3500]

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

Thanks again!

I just read this post on the 6.2 fuel economy I will keep it in mind very helpfull thanks
Vince

[Quartermiler6]

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

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