Building an Expedition TJ, give me your opinions

[OS-Aussie]

lots more power and less mileage. Best I got on the highway with stock gears and 33's was 17 mpg and with the 35's and 4.88 and SC not driving for good mpg I got as bad as 11 mpg (up to 80 mph with the trailer on (don't tell)). With the Hemi 5.13's and 39.5 tires and the 5 speed auto the best I have had is 15mpg. The only reason I changed from this setup to the Hemi was the change in tire size and the resulting need for HP for wheel speed in non expedition driving. Can you get better mileage than 11 mpg ? I don't know I never tried to max out on this aspect. But I guess that around 14 mpg was consistent. But then again with two cans on the rear and four or more in the trailer, what does it matter it's a Jeep not a Hybrid and even this sort of mileage is better than some of the big SUV's.

As far as power goes it is very hard to beat the Super charger for value and amount of power. Most bolt-ons add very little real power. $4k gets you SC and I did mine one weekend in the garage (not counting the computer reprogramming). I have used cold air, chips etc on the Jeep and nothing did as much for seat of the pants power, except the Hemi......

 

[robert j. yates]

lots more power and less mileage. Best I got on the highway with stock gears and 33's was 17 mpg and with the 35's and 4.88 and SC not driving for good mpg I got as bad as 11 mpg (up to 80 mph with the trailer on (don't tell)). With the Hemi 5.13's and 39.5 tires and the 5 speed auto the best I have had is 15mpg. The only reason I changed from this setup to the Hemi was the change in tire size and the resulting need for HP for wheel speed in non expedition driving. Can you get better mileage than 11 mpg ? I don't know I never tried to max out on this aspect. But I guess that around 14 mpg was consistent. But then again with two cans on the rear and four or more in the trailer, what does it matter it's a Jeep not a Hybrid and even this sort of mileage is better than some of the big SUV's.

As far as power goes it is very hard to beat the Super charger for value and amount of power. Most bolt-ons add very little real power. $4k gets you SC and I did mine one weekend in the garage (not counting the computer reprogramming). I have used cold air, chips etc on the Jeep and nothing did as much for seat of the pants power, except the Hemi......

Your experience pretty much replicates mine in some areas. I am averaging between 11 and 13 with my Hesco equiped 4.0 which basically means I lost about 1mpg as compared to stock. I can live with that as I was able to obtain another 30HP and 35lb/ft of torque over my stock dyno baseline.

The build cost me approximately 5K which puts me squarely into supercharger territory. The supercharger would have been a much easier install with alot less downtime but I also have as part of my build, a brand new motor which is something I would not have had with a supercharger install so I think in the long run, I am a bit further ahead from a relaibility and total cost POV. I had 93K on my stock 4.0 when it was swapped out and over time, I would not be comfortable with strapping a supercharger on a motor with that many miles on it and expect it to run for another 50-100K.

I also considered a V8 swap and looked at the hemi but that was getting into stupid money territory for me and I simply couldn't justify it mentally.

In the end, I think that getting any kind of decent fuel economy in a Wrangler is just not going to happen no matter what the build. More improtantly I think is getting reliable power to pull a trailer with. The good thing is that there are different choices for those with different preferences and wallets.

 

[OS-Aussie]

The good thing is that there are different choices for those with different preferences and wallets.

yep, if we had more money we could all drive Rovers :wings: :wings:

 

[Lawrence]

it's a Jeep not a Hybrid and even this sort of mileage is better than some of the big SUV's.

I agree that buying an SUV for its gas mileage prowess makes as much sense as convincing people that Santa Clause does exist. That’s not what I was after. I should have been clearer as I was merely interested in your 35+4.88 combo from a power/behavior standpoint. How did it do driving the Jeep by itself in various terrains, how did it do with the trailer on the same terrains, etc… Basically what you liked and didn’t.

 

[86cj]

OS-Aussie,

I am curiuos about what kind off mileage the Hemi would give with a 33x10.50 or the 33x11.50 285's...You have so much data already.....And the "ROF optimized" 5:13 ratio..... (those 39's got to be MPG killers).

If you soft pedaled it unloaded, then fully cramed towing on the open road at 70mph. I could then justify to myself the visit I made to AEV's shop and disscused the simple Hemi swap..

I just think the Hemi working less at high speed pushing the wind than the 4.0 could improve Hwy mileage a bit. Does your Hemi have cyl shut off ? My mileage drops due to the wind speed and direction alot. Around town I would not expect an improvement due to obvious juvenile behavior.


Oh and OS-Aussie that is a Big Bad Expo style rig for sure....A Hemi and a Maggiolina?:drool:

 

[Lawrence]

OS-Aussie,

I am curiuos about what kind off mileage the Hemi would give with a 33x10.50 or the 33x11.50 285's...You have so much data already.....And the "ROF optimized" 5:13 ratio..... (those 39's got to be MPG killers).

If you soft pedaled it unloaded, then fully cramed towing on the open road at 70mph. I could then justify to myself the visit I made to AEV's shop and disscused the simple Hemi swap..

I just think the Hemi working less at high speed pushing the wind than the 4.0 could improve Hwy mileage a bit. Does your Hemi have cyl shut off ? My mileage drops due to the wind speed and direction alot. Around town I would not expect an improvement due to obvious juvenile behavior.

I wouldn't do the Hemi swap for gas mileage purposes but rather for having the power available in just about any circumstances. I don't think gas mileage can be worse than what it is now, and if it is, so be it, at least it would be a lot of fun to drive.

AEV will do the swap for about $19K if you are patient, really really patient. On top of that, it would be your responsibility to make sure it passes emissions. Here in Cali, I know of 3 shops that have performed it, that can do it for about $15-$17K, and that can pass referee.

However, the downside to doing a Hemi swap is that it is not as simple as stuffing the engine and tranny in the TJ. You'd have to look at what the next weakest link will be and you'd have to most likely replace your axles, among other things. So, in reality, it becomes a lot more costly all of a sudden.

 

[OS-Aussie]

I don't think tire and gear size will change the mileage much due to the issue with the right foot. You are totally correct the rolling mass of the big tires eats the gas right up. However with more power and torque 33's would not require 5.13's or likely anything over 4.56.

On the Expedition size I just came back from a month away and the Jeep and AT never moved, as we took the Super Duty and RV instead to allow the wife to work remote via the Data Storm. Horses for courses ....

The Jeep is some what of a money pit as you suggest with upgrading ... one thing breaks another. The mod list is very long. The Hemi does have MDS but it is not being used due to which computer I have.

However I think we did more and went more places when it was closer to stock and did not worry and not getting home so much.

A true expedition rig needs to get you home, which is likely more distance than you can walk. So things that don't ensure that are not very good mod's.

My Jeep has been more on the rock crawling side of the fence, more so than expedition side, hence some of the more over the top selections.

I often think a new Diesel Grand and King Kamper is a hard setup to beat here in the US. Being Australian has something to do with this also. In Australia however it would be either Toyota or Landy.

Did I get lost on this thread somewhere......

My view for Expeditions, is close to stock as possible to meet your needs and expected terrain. Know how to fix what you have and carry the spares and tools to do it yourself. I think sometimes we also get carried away with what we really need to get there and back. I know my grandfather traveled western Queensland in the 50's / 60's in a 2 wheel drive car and in the trunk he had one set of chains, a set of tire levers, patches and a hand pump. Even fixed flats by stuffing the tire with grass. Makes me think of split rims.....

Oh, stop me now...