38.4 mpg?!! That's with 3.07 axle gears and 30 x 9.5 inch tires, correct? So that's a 250% increase over stock? Do you ever take this off road?

If I ever get my YJ project off the ground, it will likely have 31 x 10.5 inch tires and 3.55 gears, plus a 4:1 transfer case gearing.

 

The 38.4 was a one time event. I look more at the 3 tank average which looks at the total miles and total fuel used over 3 consecutive tanks. There's lots of large spikes in the single tank data. We'll see if the average continues to increase or not.

You're correct on the axles and tires. The only off roading I've done was driving through our family forest areas to get to a an old hickory tree that blew down in a storm so I could chain saw it up. Think I'd want more lift if I was going to be doing much off roading.

 

Even if 35 is your average, it's still better than 18-20 I get now with a 4 banger (16-20 with my I6 TJ). I won't see as great of fuel economy as you do, due to the lower 3.55 axle gearing. I chose this gearing based on the difference in volume between the 30x9.5 you run and the 31x10.5 I run. I'll run higher rpm's, but should not suffer the inertia penalty. The 4:1 T/C ratio is make up for going to higher gearing on trails and handling the extra torque of the diesel.

 

Not sure what I help by posting in this thread but here is something else.

I think under most conditions if I could do the same 63-65 at 1650-1700 instead of 1800-1850 I'd do better than my 19.35 average over 250+ fill ups.

MIGHT put EGT too high though.

I'm not at all displeased with 19.35 however as my truck weighs about 8,000 depending on the parts supply for my work.

 

Thats the same tube I have. Contact your dealer, and see if they have a way to exchange it. I have heard of a those guys doing part exchanges. I will look for that paint number next week.

 

I'm doing my homework on putting a b3.3 in a early toyota pickup. I've liked the motor ever since I saw it in a chipper. I have a bunch of older toyota parts and a truck laying around so I may give it a go if I can do it on the right budget. Look like the r151 tranny will bolt up using the ax15 adapter and I just happen to have one collecting dust on the shop floor.

Cheapest mechanical motor I can find new is $4k. If anyone knows a better source please let me know. I'm located in NC. I wouldn't mind a good used engine either.

Thanks to everyone here for posting the wealth of info on this site.

 

Good luck with your conversion.

Found this interesting. More aerodynamic work being done on helping the rear of bluff body vehicles to improve mpg's.

http://www.greencarcongress.com/2008...er-d.html#more

Filled up again. Upper 38's. Average for the last 3 tanks is 37.7. Seems too good. If I assume a ~10% improvement in Cd due to aero mods, a ~10% improvement in BSFC due to the mods to the injection pump timing and injectors, then I can calculate a theoretical mpg average at ~55mph of ~39 mpgs. But still . . .

Also, every once in awhile I'll search the net to see who else is doing the 3.3 Cummins conversion. It's kind of fun to see it spreading around the country. Its being done in Chevy's, Ford's, Toyota's as well as many Jeeps.

However recently came across something that disturbed me.

http://www.solutionhybrid.com/jeep.w...ngine.at.30mpg



Seems they've lifted entire sections of our thread and are claiming credit for it.

For example, compare page 8 post #109 in this thread about a spreadsheet using Cd and frontal area to calculate HP requirements.
https://www.dieseltruckresource.com/...=112807&page=8

Or page 9 post #126 of this thread to their comments about emission data.
https://www.dieseltruckresource.com/...=112807&page=9

Or page 14 post #196 about BSFC and NOx versus engine timing.
https://www.dieseltruckresource.com/...112807&page=14

Most of it appears to be directly copied. I'm glad they're promoting it, but it doesn't quite seem like the right way to go about it.

 

Hey TDI,

Why don't you register at that forum and post a link to the " 40 some pages of info " he referred to ( which we know he is referring to this thread ) and BURST his copying bubble !!! !! Maybe throw in a few licks to his JAW while beatin him down !!

 

I don't know . . . tempting. But I've never seen anything good come from doing that. Usually just causes even more bickering and hard feelings. The internet has enough of that the way it is.

I wouldn't mind him using the info if he'd cite the sources. Understanding is advanced by building on other peoples work, but we should try to cite that work. When that doesn't happen people tend to hoard information which, in my opinion, hinders progress. Oh well, hopefully it won't shut down the free exchange of ideas here where so many people have contributed.

 

I would just start asking him some real technical questions, have a little fun at his expense......

Obviously he will not be able to answer coherently.

 

Outright plagiarism is the issue! I'd notify top and let him have a go, moderator to moderator!

I never have appreciated anyone not giving due credit.

 

Guy's I have been following this thread for about a year now (I've been in Afghanistan for the past 10 1/2 months). I have been wanting to put a diesel in my Bronco II and the 3.3 seems to be the best choice based on weight, size and power output. The information you have provided is great and I can't wait to get started. You have solved almost all of my expected issues. I know that I will have to change the transmission since there are no adapters to the Colonge V6 pattern. So my one question is should I go the Chrysler (Jeep) route with an AX15/NV3550 or the Chevy route using the NV3500? As soon as I get home I'll start collecting parts and tearing down the BII. Again thank you all for providing inspiration and information.

 

Don't know why you're in Afghanistan, but if it's for being in the armed forces then thanks for your sacrifice.

I'd probably choose whichever combo works out for the least hassle and $'s. Seems like it can be done either route you're considering.

Please let us know what you do and how it works out.

 

I'm active duty military....currently in Kabul training the Afghan military. Based on what I've read it would seem that using the Chevy adapters and NV3500 would be the least hassle (fewer parts). I guess alot depends on what Transmissions/Xfer cases are availble at the salvage yard. Since you are just down the road from my home station (Rock Island/Davenport) maybe I'll get to see your jeep sometime.

 

Thanks. I appreciate your efforts and your willingness to risk your life to defend this country and protect its citizens.

I think the largest consideration between the AX15 and the NV3500 is the overdrive ratio. The AX15 has an OD ratio of 0.79 and the NV3500 is 0.73. These ratios could(should?) affect your selection of tire size and axle ratio. With either transmission you can use the NP231 transfercase specific to that transmission.

Other considerations are flywheel weight, flywheel balancing, clutch size and shifter location.