What kind of increase could I expect?

Ghost · Oct 18, 2004

Ok so I have a stage 3 mopar cam now gettting a 4.0L TB (which is supose to be bigger than the stock 2.5L) and thinking of adding bigger injectors to the mix.... will it all work well together for my littel 94 2.5L or am I asking for trouble?

Dr. Dyno · Oct 18, 2004

If you use the 21lb injectors from a '91-'95 4.0 together with the Stage 3 cam and 4.0 TB, you'll see a nice increase in performance.

Eagle · Oct 18, 2004

HIJACK!

Hey, Dr. Dyno, related question: Early (Renix) throttle body injected 2.5L. If a Mopar Stage 2 cam were installed with no other mods, would the stock injector handle it? I hope so, because that one injector costs more than an entire set for a 4.0L!

Cam specs for the 2.5L Stage 2 are identical to the 4.0L Stage 2 cam.

Dr. Dyno · Oct 18, 2004

Yeah, should be no problem. Most injectors can handle at least a 10% HP gain over stock and usually more like 20% before larger injectors become necessary.

Ghost · Oct 18, 2004

So with just the TB and the cam I could probalby run the stock injectores for a mild increase but for even more of an increase add bigger injectors?

fordtech · Oct 18, 2004

I think higher injectors would be too much. Do you have any exhaust mods? Adjustable map? Ignition system? Any other breathing mods, ie. port and polish on intake or head? I think the stock injectors should be able to handle a large TB and cam. I would go the direction of an adjustable map to adjust fuel first.

Eagle · Oct 19, 2004

Ghost said:
So with just the TB and the cam I could probalby run the stock injectores for a mild increase but for even more of an increase add bigger injectors?

Ghost, I think you would benefit from larger injectors. I asked about a Stage 2 cam, which isn't terribly radical. Stage 3 is a bit more cam. Combine that with the spacer and you could be borderline lean-run. A lot of the stroker guys encounter this when they first get their new stroker motors running.

Given my druthers, I'd do a new injector even with a Stage 2 cam, but that one throttle body injector sells for around $250! :scared:

old_man · Oct 19, 2004

I built a 2.5L +.060 w/Stage 3 cam and Clifford headers. It was the throttle body injected setup. I had absolutely no problem running lean. It was great on the trails but just didn't have the lungs for the mountain passes on the interstate.

Rough 01 · Oct 19, 2004

I say just put a 5.7L Hemi in it and be done!

It's late and I'm in a silly mood! :cheers:

Later,
Rough

Ghost · Oct 19, 2004

Rough 01 said:
I say just put a 5.7L Hemi in it and be done!

It's late and I'm in a silly mood! :cheers:

Later,
Rough

Well that brings me to my other XJ project that I'm collecting parts for......

Ghost · Oct 19, 2004

fordtech said:
I think higher injectors would be too much. Do you have any exhaust mods? Adjustable map? Ignition system? Any other breathing mods, ie. port and polish on intake or head? I think the stock injectors should be able to handle a large TB and cam. I would go the direction of an adjustable map to adjust fuel first.

No other mods as of yet. I want to look into the other things you mention but my knowledge of FI performance is limited. I know bigger air and fuel mean more power that is about all I know! LOL! I want to put the banks SS header on it but that will be a while.

MudDawg · Oct 20, 2004

Hijack....LOL.....Does anyone have any experience with the Weber aftermarket FI system?? My 2.5 is carbed...and the harmonic balancer rework and CPS relocation kit and the rest of the stuff for a MPI put the cost in the same ballpark...Or is there an aftermarket ECU that will work as a stand-alone fuel managment system?

CW · Oct 20, 2004

What kind of power are you guys getting out of these engines? I am looking at an mj with a 2.5L thats carbed with 190,000 miles on it. I can get all the fuel injection junk for around $80. I was just going to swap in a 4.0L but building a four banger up could be a fun project. I was thinking I would bore it out, swap multiport injection on, 4.0 HO TB, injectors, and a cam.

Ghost · Oct 20, 2004

MudDawg said:
Hijack....LOL.....Does anyone have any experience with the Weber aftermarket FI system?? My 2.5 is carbed...and the harmonic balancer rework and CPS relocation kit and the rest of the stuff for a MPI put the cost in the same ballpark...Or is there an aftermarket ECU that will work as a stand-alone fuel managment system?

Don't bother... find a 91 - 96 FI 2.5L.... The heads are the same from 84 to 96 I know for a fact. Even the blocks are the same. I got a 94 body harness, since the connector to the engine harness changed three times. I am getting decent power out of my 94 MPI set up. I did the whole swap, engine, tranny, tcase, body and engine harness, plus stock ECU for about $500.... The best way to do it is to find a wrecked 91-96 2.5L XJ... They are rare but are out there. Depending on the year of your XJ its an easyer swap then a 4.0L..... If your MJ is a pre 87 that is.

What kind of increase could I expect?

Ghost

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