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Cummins into an XJ... This will take a year.

cserou

NAXJA Forum User
Location
Sacramento, Ca
I've been on NAXJA for a minute now, and although I own 4 XJs, I've never posted a build thread because I haven't felt like I was really doing anything that different. However, I am rebuilding my '99 2dr 5 spd into a rock crawler since I've moved out to Northern California, and the unibody is messed up anyway. Since I'm going so far off the beaten path, I decided to do a thread in hopes of inspiring others and gaining some intelligent input. Why, you may ask? Because all those toyota guys get on my nerves.
So far, I have a boosted 4cyl Cummins QSB4.5, with an SAE #3 flywheel housing
Chevy Dana 60 and 14 bolt axles
Divorced 32 spline NP205 that I'm rebuilding right now and converting to a twin stick
Chelsea PTO for said t-case and PTO winch (yeah, a diesel powered winch)
Chevy hydroboost and master cylinder
HMMWV beadlock wheels

What I intend to do is build frame rails outboard of the unibody's frame rails and add to its structural integrity by putting strategically placed square tube inside the unibody frame rails and tying it together. A cage goes without saying.

I will also need to build a seriously heavy rear bumper to help add weight to the rear.

I am going to have to run full hydraulic steering and because of the backspacing of the beadlocks, and so that I can push my front axle forward.

In order to push my front axle forward, I will have to use a coilover suspension in the front.

Instead of doing a doubler, I am going to mate up a planetary from another transfer case (probably a 203) behind my transmission as an independent underdrive unit so that I can still put my divorced 205 where I want it. This will also help offset the weight of the Cummins and winch... but not all that much.

For the rear suspension, I am leaning towards a 3/4 elliptical set up because of the inexpensive cost, but I'm open to suggestions.

The hard parts are:
Finding a manual transmission that isn't too long and a flywheel housing for the Cummins. I have a couple of ideas, but I may have to go with a 2wd and change the output shaft. I would prefer to use a hydraulic clutch so that I have one less linkage to make from scratch.
Finding a high enough flow power steering pump to run both the hydroboost and hydro steer.
Keeping it cool. The XJ doesn't offer much surface area for cooling.
Deciding what color to paint it.
 
:thumbup:


Why the QSB4.5, why not an old 4BT? Seems like then you could use alot of the stuff from a Dodge Ram 6BT drivetain. You could run the NV4500, mount a 241/205 doubler setup off it. You could use the Dodge PS pump, they run PS and hydroboost no problem. Toss an alum radiator in the back to cool it. Buddy of mine has a big block mopar with the same tranny/t-cases setup and radiator out back with twin fans on it. Seems like a great setup and the way to go. I'd love to do a 4BT in a Comanche.
 
Well this is technically still a 4bt, but it's an ECM controlled offroad-only version. I WOULD love to use an ISB3.9 though, like I have in my box truck, because I love mechanical injection, but I have this QSB already. I may someday swap a 12v into my box truck, and then put that motor into another Jeep, but I can't have that many vehicles taken apart at the same time.
I would love to find an NV4500, but it seems like everybody wants $1500 for them. It would be cool if I could find a whole 12v truck to buy for parts...
What did your buddy do to plumb the cooling system? Aluminum tubes? That sounds like a great idea to me since I have a HUGE radiator in my garage that came out of my CUCV. I could also mount a really bid power steering cooler up front then.
 
Holy gigantic 4 banger Batman! Looking forward to seeing this. My buddy has a 68 Bronco that he's about to throw a 4bt in. Along with an NV4500. Good luck finding one of those for under a grand! He just ordered his adapter plate through advance adapters.
 
Thanks! It will take some doing, but after this, everything else will be a piece of cake. :-D


I'm almost completely convinced to go with a Muncie SM465 4 speed and build a bellhousing from scratch because they're everywhere, have a lower first gear, no overdrive, and can handle plenty of torque. I would honestly rather do more labor and spend less money lol.
 
For the rear suspension, I am leaning towards a 3/4 elliptical set up because of the inexpensive cost, but I'm open to suggestions.

.

leafs longer shackles and shackle relocation boxes will be way better and offer a ton of flex, also id definetly run a traction bar
 
dude. this sounds bad ass. lets go gurlie kick you tall leggy as in gear and get some fab work and pics up damn it!

good to know youre still rocking an XJ ;)
 
Sweet! The 4bt is also high enough compression to burn veggie oil if you want... I don't know how this ECM controlled one would like it though.

This is exactly why my buddy is running a 4bt, he can run it on anything if he wants. We work at Cummins but build fuel injector parts for the Big boys, the b series engines are built at another plant in town and in NC.
 
I have no idea the details about the QSB4.5 and the requirements for installation. Since it is an ECM controlled engine do you have access to a calibration/tune? or are you going to run what it came with?

I would not run veggie in it. You will probably require another tune/cal. I am not sure of their High pressure fuel pump and injectors but the one on my engine is sensitive to dirty fuel/alternative fuels (aka voids warranty).

Another thing that might pop up as a problem is throttle control. There is usually a potentiometer set-up or CAN messaging that controls the engine and you will have to figure out what cummins does around this.

Try and find a pinout for the electrical system asap as it will make your life easier.

is the engine an emissions engine, egr? DPF? VGT? this one -->http://cumminsengines.com/every/misc/Technology/tier4_interim_stageiiib_qsb45.page

If I think of anything else that might affect your install I'll post up. if you have any questions post up.
 
This is exactly why my buddy is running a 4bt, he can run it on anything if he wants. We work at Cummins but build fuel injector parts for the Big boys, the b series engines are built at another plant in town and in NC.

That sounds like an awesome job! I rebuilt the injectors on my CUCV and it really wasn't that hard. I also made a "high performance" injection pump out of 3 different Stanadyne pumps. They actually have a viscosity compensating device. TONS of small parts but I think mechanical injection systems are fascinating. Too bad we can't use them on gas engines.

EDIT: Have you ever gotten to take apart any MUI injectors? Those look really cool.
 
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I have no idea the details about the QSB4.5 and the requirements for installation. Since it is an ECM controlled engine do you have access to a calibration/tune? or are you going to run what it came with?

I would not run veggie in it. You will probably require another tune/cal. I am not sure of their High pressure fuel pump and injectors but the one on my engine is sensitive to dirty fuel/alternative fuels (aka voids warranty).

Another thing that might pop up as a problem is throttle control. There is usually a potentiometer set-up or CAN messaging that controls the engine and you will have to figure out what cummins does around this.

Try and find a pinout for the electrical system asap as it will make your life easier.

is the engine an emissions engine, egr? DPF? VGT? this one -->http://cumminsengines.com/every/misc/Technology/tier4_interim_stageiiib_qsb45.page

If I think of anything else that might affect your install I'll post up. if you have any questions post up.

Thanks for the input! I'm planning to run the stock programming first to see what needs to be tweaked. I'm not very good with computers, so I'm taking a high performance computer tuning class in the fall. I got pretty lucky with a complete motor with all the engine management sensors intact. I have the manual with complete wiring diagrams, but in case you haven't seen this... https://quickserve.cummins.com
You can register up to 5 engines by serial number and it has all the electrical diagrams, troubleshooting, and maintenance information online.

I'm not planning to run veggie oil in this engine... even if miraculously the ECM knew what it was getting, there would still be the problem of running 2 tanks, heat exchangers, and everything else. Plus I probably wouldn't break even by converting a trailer queen. Burning it in my tow rig is good enough for me.

The throttle control will definitely be a headache. It's designed to use an APP, like you're talking about. I'll start by looking for sensors in the jy and try to mount something creatively enough that it knows where idle and WOT are. It uses a 5v ref, so anything other than Dodge or Jeep might be made to work.

No EGR, no DPF, Holset wastegate turbo (I wish I had a VGT!), PCV only on emissions. It's the same size and design as that one, but mine is from 2005. It reminds me of the VP44 set-up.

What engine do you have?
 
For the throttle there is going to be 3 wires you need to hook up; power, ground and signal. There may be two 3 wire hookups as a safety, if it is like this then you will get a mil light if they both are not hooked up. Most potentiometers have 2 throttle tracks built in because it is the standard. Hopefully that calibration in the ECU has a wide band so just about anything will work for your throttle.

I am a Diesel Calibration and Applications Engineer
 
Sweet!
 
:thumbup:


Why the QSB4.5, why not an old 4BT? Seems like then you could use alot of the stuff from a Dodge Ram 6BT drivetain. You could run the NV4500, mount a 241/205 doubler setup off it. You could use the Dodge PS pump, they run PS and hydroboost no problem. Toss an alum radiator in the back to cool it. Buddy of mine has a big block mopar with the same tranny/t-cases setup and radiator out back with twin fans on it. Seems like a great setup and the way to go. I'd love to do a 4BT in a Comanche.

:wave:

What did your buddy do to plumb the cooling system? Aluminum tubes? That sounds like a great idea to me since I have a HUGE radiator in my garage that came out of my CUCV. I could also mount a really bid power steering cooler up front then.

I bought some 1.5" plain steel exhaust tubing from Summit Racing(straight pieces and U-bends).

Butt welded them and used rubber hose for any joints (I wanted certain sections to be removeable for servicing other parts of the jeep). Wherever the rubber met the tubing, I ran a small weld bead around the edge of the tubing to act as a catch for the hose clamps. Works perfect. I also added a drain point at the lowest point of tubing and some bleeders in the engine bay to assist with getting rid of air bubbles.

Looking back it would have been nice to TIG the tubing since I could have forseen any leaks from the start. Had to fix one area that was a PITA.

Sounds *waaay* heavy.

I'm sure people thought my drivetrain would be too heavy (Probably tipping the scales at just over 1k lbs) but I haven't had an issue with it.

400+ HP and 500 + lb-ft of torque makes it feel light as a feather :D
 
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