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Old 05-03-2012, 10:23 AM   #1
Join Date: May 2012
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Jeep YJ M90 supercharger build

Hello all,

My 4.0 YJ has been sitting around in my garage for over 3 years with rotted holes of the size of baseballs in its frame. Paying college up front + the cost of living and feeding my Mini Cooper S made it impossible to dedicate any leftover money to the Jeep.

Now that I'm done with College bills until next year, I thought it would be a perfect time to rebuild it and do what I always wanted to it, Supercharge the stock 4.0!

As of now, I'm still searching local Junkyards for a solid frame. In the mean time, I'm gathering as much info as I can on the build.
One of the reasons that I'm confident of supercharging it is because I have complete access to a CNC machine for light duty mounts, brackets, pulleys, adapters etc..

I'm planing everything out on paper before getting into it completely, and as you all can imagine I'm coming across a few obstacles.

1. Please feel free to correct me if I'm wrong, I read somewhere that the AX-15 tranny is rated at 300lbs of tq on the dot. If so, the input shaft will snap on the first dyno run when it's time to tune the engine. I'm willing to rebuild it, not swap it.

2. ECU remap, I'm thinking about running megasquirt as of now, if anyone knowns anything better to use on this application, please feel free to contribute.

3. Engine Temp!! Keeping the engine temperature down is my biggest obstacle at the moment. The M90 charger will pump 12psi at the most, even though the compression in this engine is relativelly low I'm still worried about overheating it. I believe that an intercooler is enough, but I'm starting to consider an oil cooler as well.

Stock fuel delivery is all junk. New and updated regulator, pump, and rail will be used.

I encourage you all to contribute with ideas that might help me on this one.
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Old 05-04-2012, 04:55 PM   #2
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Interested too. I have thought about putting a 2.5l together with a super charger.

The megasquirts work quite well from what I have heard. Not looked into it really.

Also thought about just running an fmu for the fuel and get an adjustable ignition box to control ignition. Not sure how to change the timing yet...

My build thread :

"A lack of planning on your part does not constitue an instant emergency on my part"
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Old 05-04-2012, 05:21 PM   #3
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a buddy of mine ran twin turbos on his 4.0 xj using megasquirt to control it it a few years back. it was badass.

he ran everything on megasquirt though, he had a twin turbo bmw too.

megasquirt is sweet. i built an ms2 for my bmw and it bench tested great but i am not computer literate enough to have got it working on the car, i found out. traded it another guy for some stuff and he plugged it and it fired right up with some programming.
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Old 05-06-2012, 10:17 AM   #4
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I might use a MSD Performance Digtal Ignition Control (Digtal 6 Plus) for ignition timing. And yes Turbos would of been sweet, but the costs would knock me out.

I just picked up an M90 Charger that came out of a 1990 ford thunderbird which included a small intercooler and some piping for $250.. I'll be taking the charger apart for a rebuild and to soda blast it and lay a nice black powder coat.

At one point I wanted to swap an S50 motor into an E30, but that would cost me $10k+ , I might turbocharge an M50b25 and drop it in a E30 next summer if the jeep up and running.
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Old 01-04-2015, 09:34 PM   #5
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Hi everyone,

It's been a couple of years, time for an update.. I wasnt able to start on the build until sept of 2014 for many reasons, but this project is nearly complete.

Nothing too crazy, there are a lot more insane builds on here other than mine. But I will be posting the full story on the entire build once its complete for those of who are interested in supercharging their rigs. Just leaving an image here so you guys can get a bit of where I am with the project as of now.
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Old 01-06-2015, 09:30 PM   #6
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when you rebuilt it any particular reason why u decided not to stroke it? thats where im at i have an 87 with i think a failing 4.2 ,and this summer once it warms up/ snows gone i planned to build the 4.6 stroker and super charge it. but i have little to no experience with computer systems. and i am going to have to put a whole system in as i am currentlly carbed how hard was it to retrofit the computer to account for the boost also what did you find out about the ax15 no one has been able to give me a straight answer on what it will handle
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Old 01-06-2015, 10:55 PM   #7
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Looks awesome! More pics and parts info would awesome. Curious on the fuel supply. More pics plz!

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frame swap , jeep yj , m90 , rebuild , supercharger

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