ECU question

[mdjdc]

I recently replaced my wifes engine in her 96 OB wagon with a 98 engine. My question is, should I find a 98 ECU for the car or should I just run it with the 96 ECU? It runs well I just didn't know if it would be more efficient with the 98 ECU

 

Thanks

[idosubaru]

i'd leave it.

[subaru360]

I'd leave it. I don't think there is much if any difference.

[OB99W]

[...]It runs well I just didn't know if it would be more efficient with the 98 ECU

I think the operative phrase here is "It runs well". "Don't fix what ain't broke" also comes to mind.

 

Since you mentioned efficiency, how's the gas mileage? If it's decent, and the engine starts easily cold/hot, idles well, accelerates without hesitation, has good power, etc., I'd leave the ECU alone.

[Rooster2]

agree with others, if it "ain't broke, don't fix it." Unless...........if you live somewhere, where your state requires a tail pipe check for pollution emissions, known as e-check, in order to register your car for renewal license plates. If that is the case, then your car could conceivably fail the e-check test because of the different ECU.

[idosubaru]

athen your car could conceivably fail the e-check test because of the different ECU.

lots of people say that but i've yet to ever hear proof that it's happened and it goes against everything we actually see and hear from others doing swaps (like myself). i don't know about other states but in MD, they have state run facilities to do it, they pay guys 9 bucks an hour to look at your check engine light (to see if it's on or off) then check emissions. if the light isn't on and the emissions are below thresholds you pass. if not, you come back and try again. it's not that complicated and they certainly don't thoroughly inspect every make/model/year/engine combo/trans combo/ECU ever made. and i know many other states this holds true as well. now...im' not saying it's impossible, and the only reason im going on this diatribe is that i don't think it's accurate to suggest to new or non-car/non-mechanically oriented people some speculation that we don't see any evidence of. people are swapping engines all the time, it's not that big of a deal.

 

california you say....well they need their own forum, i don't know anything about those freaks!!

[RallyKeith]

I swapped an EJ22 into a 96 that had an EJ25. I swapped the ECU to one from a 96 with a 2.2 ONLY because the 2.2 had a lower RPM Limit and I thought it might be nice to not over rev the engine. It made no difference in performance, gas mileage, or starting. I'm probably going to switch it back because the TCU is still looking for the extraRPMs during a WOT pull-out.

[OB99W]

[...]I'm probably going to switch it back because the TCU is still looking for the extraRPMs during a WOT pull-out.

That brings up the good point that just swapping the ECU might cause issues if a paired TCU isn't installed at the same time. "Let it be" if it works okay.

[mdjdc]

Thanks guys, I was thinking the same thing until I did a swap for a friend of mine and he wants the ECU out of the donor car because of some possible software upgrade between '96 and '97. My car is running great so I'm going to leave well enough alone.

 

Thanks for all of the info and confirning my initial thoughts on the matter.

 

If he want to do it on his car, then he can have the ECU and whatever happens is his affair.