Nice conversion and MPG's! Wondering if you had any idea if you think a 4bt 3.9 liter could get similar mileage with the same setup as yours?

 

Well, off the cuff I'd say since the 3.9 weighs ~200 lbs more the rule-of-thumb that you lose ~1 mpg/100 lbs would translate into roughly ~2 mpg less for the 3.9. Then the 3.9 would require more lift to clear the front axel than the 3.3 so your aerodynamics would likely be worse so you'd take additional fuel efficiency hit there (I don't know how to quantify that). And then for steady state driving where you need X hp (assuming equal tires/gearing) the 3.3 should be operating closer to its peak torque at that rpm than the 3.9 so it's thermal efficiency should be higher (based on the BSFC/rpm contour plots I've seen on other diesel engines).

So I'd guess roughly 2-4 mpg's less for an equivalent setup would seem reasonable. But that's a swag on my part.

 

UPDATE**

My QSB 4.5L ate my AX-15 for lunch !

With research I found that a 1994 to 1999 Dodge Ram 2500 with 5.9L V8 and 4 wheel drive can donate its Bellhousing and NV4500 transmission to my project !
The bellhousing will bolt right up to my Pheonix Castings adapter; I can reuse the whole clutch assembly I presently have ( the input of this NV4500 is the same as the AX-15... 1 1/8 by 10 spline !) and I already have the Dakota V8 slave cylinder which will bolt right into the bellhousing. The output of this NV4500 is 23 spline and my Dana 300 is supposed to match the bolt hole pattern of the NV4500 ( could not find out if that meant even if it is flipped, but since I bought the Novak Dana 300 adapter flip kit, I have it covered anyways. )
The whole assembly is supposed to be within 1 1/2 inches of my present setup so I should be Okay ! The overall length of NV4500 with 4x4 output housing is 18.5 inches !
Here are a couple pics of the bell and clutch slave all together with throw out bearing and actuator !



And I measured from the back of the bell to the trans shifter hole and it seems to line up with only minor trimming .... the NV4500 case is only 12.37 inches overall and my shifter hole in the floor is 12 inches from the the mounting face of the bell ......will have to wait til this weekend when the NV4500 arrives from Michigan. It only has 67000 miles on it, and it only cost $400 plus $185 to freight ship it to south Louisiana. It did not have a bellhousing so I found one in Oklahoma for $100 shipped to me !

 

What happened to the AX-15?

Check the 5th gear nut on your NV4500. Had one fail, and the second tranny was working it's way to failure. Just my experience anyway... I would at least bring the tranny into a shop and have it looked at while it's still out of the jeep.

If you want to know more about the 5th gear nut thing, look here, it's the best description I can find: http://quad4x4.com/NV4500%205th%20Ge...0Solutions.htm

 

Hey Kriesel,

Went on a small dirt mound roughly 36 inches tall and it was moist from rain, since I have not installed my detroit lockers yet, it spun the tires in the dirt. I tried to rock it out back and forth and on the second time I applied too much gas and when I shifted out of reverse into neutral the handle moved, but nothing else, so it is stuck in reverse and the shift handle is in neutral. Prolly the shift fork, but it was gonna cost a few hundred in labor to tear down the trans and tear down my spare trans and replace forks; when I know the trans is only rated for 300ish ft lbs and I am putting out 360, I figured it was only a matter of time. So rather than waste money for something else to break, I just upgraded it now. It improves my crawl ratio with the 5.61 first gear of the NV4500 also!

Also, thanks, I have read that the fifth gear can be a problem. I will check it, and make sure I don't leave the trans in fifth gear and let the engine lug down below 1400 with the accelerator mashed to the floor.

 

So no tractor pulls in the YJ?

 

At least not in 5th gear!! Lmao


EDIT****

My NV4500 came in yesterday. This NV4500 had 67000 miles on it. It had been sitting on the salvage yards shelf for 8 years. ( but they were thoughtful enough to duct tape the shifter and output holes, preventing any moisture or dirt from entering the case! ) I verified it had no rust on any gears or bearings, sealed it up, and washed the dust off before applying 2 coats of rustoleum to prevent surface rust !!

This picture was taken without the camera's flash on !!


By redrilling these two holes at the top I will be able to bolt my flipped Dana 300 right up to the NV4500 without the Novak 1 inch thick adapter ! So, I have only gained 1 and 1/8 inches to my drivetrains overall length, I should not have to alter my brand new Tom Woods driveshafts; Thank you LORD !!



You can see more pics at my flickr account.

 

Sorry I have not updated recently.

Got everything together and the weather improved to mid 60s to 70s so I took the hard top off and have added some BF Goodrich all terrain 35x12.50x15 tires to lower my rpm's and now I am having too much fun driving the ******* off my new tires to update. My fuel gauge, voltage gauge, temperature gauge, and oil pressure gauge all work and I am using a GPS for speedometer and trip odometer. The motor is NEW and not broken in but I am estimating around 21 for initial fuel economy around town and this is with the 31x10.50x15 tires!!

The only complaint I have about the vehicle at all is the fact that I used the 5.9L motor mount. It is a bit too hard and it transmits a little more than ideal vibration to transmit to the frame and into the cab BUT this is only when idling at a red light. I may attempt to re-engineer the motor mounts sometime in the next 5 years, but it is surely not on the top of the list.

OH MY GOD THIS IS SOOOOO MUCH FUN TO DRIVE !!

 

Thought you may be interested.

I have run a few tanks of diesel through it !! I am using a GPS for my trip odometer and speedometer. I have a very small fuel leak at the pump to consider into this as well. Any way, This is a brand new engine and not "broken in" yet by any means.

I averaged 21.9 for the first tank. This is with 31 inch Procomp X terrain tires
I averaged 24.6 for the second tank. This is with 35 inch BF Goodrich all-terrains.

I find this extremely promising !!

 

That's awesome, I'm getting about the same mileage with my brand new engine as well, and on winter diesel.

I am somewhat more curious about your gas pedal wiring, and how you wired up to the ecm on the engine. Mind sharing some of that? In my free time lately, I've been playing around with a QSB5 and a QSB7

 

I purchased a potientiometer out of a 2005 Dodge Ram (as long as it is 2003 to 2007.) It is considered the "williams"! On my wiring diagram for my ECM it gave the option of either the "robert shaw" or "williams" for potentiometer. I simply wired it in just as the wiring diagram said it needed to be. The ECM had to be told which one it was and that it was there to talk to(turned on!); but that was it ! It worked like a champ!

I am unfamiliar with a QSB 5 AND 7. The Cummins paperwork only talks of the QSB 3.3, 4.5,(4 cylinders) and 6.7(6 cylinder) !! Help me out !!

I almost forgot my RPM's seem to be topping out at 2100; so I may take it back to Morgan City (mid-south cummins) and have them turn the computer value higher maybe 2800 or 3200 (somewhere in between) what do you think ??

 

The QSB5 is the 4.5, and the QSB7 is the 6.7. It's like saying the Chevy small block 350 is a 350, when in actuality it is a 349. Kinda round it up to the next number. It's just a shortcut name kinda I guess. I think on official data sheets it is the 4.5 and 6.7 though.

The engine speed that you want would depend on which exact engine model you have I suppose. And then whether they would turn it up since that engine you have didn't come with the RPM at a higher value in the first place. I think the base engine is rated for a redline of 3,750; but if it were me I would set the ecm at 3,000 or 3,500 maybe, and see how that works out. If there is no need to set it right at the redline, why go that high I would say.

Do you know how they are connecting to the engine? Is it an industrial style plug used for an Inline5 thing, or is it an automotive style OBD plug?

 

Why does Cummins list a QSB4.5 and QSB6.7?? Never heard of the QSB 5 and 7 like you say

Also, as for Cummins adjusting the redline...it could be simple, or hard. Until they plug in, they probably won't know.

Chris

 

Like I said, it's not the official name to call them the 5 and 7... We call it that here at work now and then is all . It's like a nickname, not the official title...

For example, I google searched "Cummins QSB5" and this was the first link:

http://www.google.com/url?sa=t&sourc...SzZldBKIIa3ByA

 

The last time I googled "Cummins QSB 4.5L", I was in the top 7 seach results !! I tried it today and my flicker acct came up as the first result!! Too Funny !

On my engine, at the moment, They are using the 2 pin or 3 pin and the Inline5 tool. Mid South Cummins does mostly marine stuff. They were quite impressed with my Jeep when I brought it in.
As far as the future, I can either use the 9 pin under the dash of a car or I can use the 9 pin like what is found in a Big Rig. I have not decided which one to go with. Thank You very much for your insight on what to set the red-line at. I appreciate it ! and thanks for clearing up the QSB 5 AND 7 thing, I understand now.