tmaxx411 Posted January 30, 2014 Posted January 30, 2014 is it possible to swap a 2.5 tbi to a 2.5 mpi? I'm guessing it would be a ecu/wiring harness/head swap? what trucks would it come out of?
Eagle Posted January 30, 2014 Posted January 30, 2014 Any 1991 or newer Jeep YJ, TJ, XJ or MJ. Chrysler changed from throttle body to multi-port on the 2.5L in 1991. But it's also a Chrysler ignition, so you will need a new ECU and under-hood wiring harness.
tmaxx411 Posted January 30, 2014 Author Posted January 30, 2014 ok. looks like i need to start junkyard hunting
Jeep Driver Posted January 30, 2014 Posted January 30, 2014 Consider dollars and effort........any gain will be negligible. Tune what you have, you'll be surprised.
tmaxx411 Posted January 30, 2014 Author Posted January 30, 2014 i'm going to be honest here. I'm not looking for any "gain". its more to give me something familiar to troubleshoot when something goes wrong. TBI is a completely new, and foreign system to me. and it seems like a rather inefficient design.
Jeep Driver Posted January 30, 2014 Posted January 30, 2014 That's a whole lot of effort to avoid a new familiarity. Clean it up, tune it up, and come to understand it. Mine runs extremely well, I'll put it up to any MPI 2.5 anytime. Efficiency? 22-25 But.........nothing more than my opinion............do as you will.
Eagle Posted January 30, 2014 Posted January 30, 2014 Consider dollars and effort........any gain will be negligible. Tune what you have, you'll be surprised. I disagree. The gain will be worthwhile. The throttle body injected version produced 117 horsepower at 5,000 RPM and 135 foot-pounds of torque at 3,500 RPM when it was introduced in the 1986 model year. This was raised to 121 horsepower at 5,250 RPM and 141 foot-pounds of torque at 3,250 RPM for model years 1987 through 1990. The final, multi-port injected version produced 130 horsepower at 5,250 RPM and 150 foot-pounds of torque at 3,250 RPM. If you get the system from a '97 - '00 Cherokee, you'll also get OBD-II, which will allow using a hand-held scanner to read trouble codes.
Jeep Driver Posted January 30, 2014 Posted January 30, 2014 Consider dollars and effort........any gain will be negligible. Tune what you have, you'll be surprised. I disagree. The gain will be worthwhile. The throttle body injected version produced 117 horsepower at 5,000 RPM and 135 foot-pounds of torque at 3,500 RPM when it was introduced in the 1986 model year. This was raised to 121 horsepower at 5,250 RPM and 141 foot-pounds of torque at 3,250 RPM for model years 1987 through 1990. The final, multi-port injected version produced 130 horsepower at 5,250 RPM and 150 foot-pounds of torque at 3,250 RPM. If you get the system from a '97 - '00 Cherokee, you'll also get OBD-II, which will allow using a hand-held scanner to read trouble codes. I was going to post this--- and decided not to........ Let me suggest this to you....... My wife drives a 97 XJ with the 4.0 and I keep hers running well also (in the two years we have had it it's been surprisingly trouble free). In the summer I pull a trailer with a Kubota that I use to mow several lots here in the mountains...combined weight, trailer, tractor, mower attachment, is around 3000lbs. My truck with it's little 2.5 pulls it up these mountain roads with very little trouble. I can pull the trailer with either one, the MJ or the XJ. I choose the MJ, mainly because I do not worry about getting dirty and getting into her Jeep. Comparing the two, does the benefit of the 4.0 cause me to start swapping engines and transmissions and harnesses? The point is, I have a real world comparison. If he wants a project, so be it, it's his. For what ever he will gain, horsepower or familiarity, consider the effort, time, money............and what is the payoff?
Jeep Driver Posted January 30, 2014 Posted January 30, 2014 If he's going to go through all that.......he might as well do a 4.0 swap, he'd be better off.
Jeep Driver Posted January 30, 2014 Posted January 30, 2014 Also.... I have a trans out of a 94 and I know the CPS is different........Renix to Chrysler..........I suspect the fly wheel is different too.
mnkyboy Posted January 30, 2014 Posted January 30, 2014 The flywheel is different between the Chrysler and renix systems whether its a 2.5l or a 4.0l. I'm actually getting ready to do this swap, I have an entire 95 YJ engine,wiring, and computer. I havent laid out the wiring yet but it looks fairly straight forward, the MPI harness looks pretty stand alone with only a few wires tieing into the vehicle harness.
Comanchemodder Posted January 30, 2014 Posted January 30, 2014 Distributor is different too. And maybe the coil; the RENIX Coil may work, but the MPI coil looks physically different.
mnkyboy Posted January 30, 2014 Posted January 30, 2014 Luckily for me I have an entire 95 YJ for parts.
mnkyboy Posted January 30, 2014 Posted January 30, 2014 As far as I know the Block and head never changed.
Eagle Posted January 31, 2014 Posted January 31, 2014 The flywheel is different between the Chrysler and renix systems whether its a 2.5l or a 4.0l. I'm actually getting ready to do this swap, I have an entire 95 YJ engine,wiring, and computer. I havent laid out the wiring yet but it looks fairly straight forward, the MPI harness looks pretty stand alone with only a few wires tieing into the vehicle harness. I believe it should work as a standalone. My reason for thining that is that the Mopar Performance Catalog used to offer (and perhaps still does, but these days it's only on-line and I'm old enough that I love thumbing through paper catalogs) an MPFI conversion for the carbureted 4.2L YJs. That conversion was essentially the EFI and underhood wiring harness from a '95 YJ. If it works for the 4.0L, it should work for the 2.5L.
tmaxx411 Posted January 31, 2014 Author Posted January 31, 2014 so to do this, i will need an ecu, wiring harness, intake, throttle body, air box, fuel injectors, rail, distributor, and flywheel. anything else i'm missing?
carnuck Posted February 12, 2014 Posted February 12, 2014 My son sold his '86 MJ 2.5L to a guy with a TJ and everything bolted right on. Didn't even change the head.
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