ECU tuning differences.

[987687]

I'm wondering if there's any difference in the tuning of stock ECUs that affects power output any.

I have a 96 legacy, 2.2, 5speed. No EGR. And it has the stock ECU.

Sitting in a box, I have the ECU from an outback limited, 2.5, auto tranny WITH EGR.

 

So for the heck of it, I plugged that computer into my legacy. Took it a while to idle right, but it learned how to do it eventually.

Some things I noticed:

Got a redline of 6500 instead of 6000

SEEMED to have more power, a little less low end, but a bigger curve overall. Could very well be butt-dyno calibration....

And no CEL for EGR.... I expected a CEL for that because it's an EGR computer running a non-EGR engine. And I've heard everyone say that there's no way around an EGR CEL with no EGR...

Also, during my day driving around with it, after a WOT pull in 2nd to redline I got a CEL. Pulled over and it was for a misfire. Cleared it, and didn't come back in the next 50 miles. So probably a fluke... Just mentioning it. I don't usually drive this car very hard, so that's probably what triggered it.

 

 

Anyway, do you really get more power with the 2.5 ECU running the 2.2? Or just my imagination?

[GeneralDisorder]

That was my impression as well - but it could partially be the the 2.5 torque converter and gearing on the GT. I swapped in a great 2.2 in place of a 2.5 that was destroyed inside..... I was pleasantly surprised with the power actually.

 

It likely has different timing characteristics and the obvious higher redline, etc.

 

GD

[987687]

Hmm, glad that I'm not just imagining a difference.

 

What about the EGR? Shouldn't the computer have been upset that my engine doesn't have an EGR on it? The stock computer obviously knows it doesn't have an one because it came that way from the factory.

 

 

an interesting experiment would be to put my 2.2 computer into the 99 outback with the 2.5DOHC and see what I get

Edited January 27, 2011 by 987687

[wtdash]

The stock computer obviously knows it doesn't have an one because it came that way from the factory.

 

Can't confirm this, but your post kinda does. ECU will work w/either trans...so maybe that's part of it????....The ECU has a pin for Automatics (I know the '91-94 Turbo ECUs do since they all work for either trans), and if the harness is 'pinned' then the ECU reacts accordingly.

 

 

Although my '98 Forester EJ25 w/a 5-speed DOES have EGR, too, .....Here's a '99 EJ22 5-speed Legacy on Ebay w/NO EGR.

[nipper]

IF the EGR send a switch like signal it could really care less. I am not feeling well so I do not remeber how it sends a signal to the ECU.

[987687]

Can't confirm this, but your post kinda does. ECU will work w/either trans...so maybe that's part of it????....The ECU has a pin for Automatics (I know the '91-94 Turbo ECUs do since they all work for either trans), and if the harness is 'pinned' then the ECU reacts accordingly.

 

 

Although my '98 Forester EJ25 w/a 5-speed DOES have EGR, too, .....Here's a '99 EJ22 5-speed Legacy on Ebay w/NO EGR.

 

'99 doesn't count because that's a phase2 engine.

The 99 OBW in my driveway is a phase1 because it's DOHC, that's a manual and has EGR. But I was thinking putting the 2.2 computer to run the 2.5 just to see how it goes.

 

The auto thing doesn't really matter, the ECU couldn't care less, it just sends a tach and speed signal to the TCU.

 

I thought there was something about swapping engines where if you didn't have EGR on the engine, but the car came with it, you'd always have a CEL that couldn't be killed.

[idosubaru]

'99 doesn't count because that's a phase2 engine.

99 legacy is Phase I. only 99 Foresters and Impreza RS are Phase II. manual trans are easy to find either way - with or without EGR are common. it's the non-EGR auto trans that are rare.

 

I thought there was something about swapping engines where if you didn't have EGR on the engine, but the car came with it, you'd always have a CEL that couldn't be killed.

correct. you're doing something different than the threads/issues you're referencing though. you're talking about manual trans, those issues are with auto trans equipped engine swaps.

 

the auto equipped non-EGR OBDII vehicles are rare and there's no solution so far for swapping to non-EGR. except to live in a state like i do that doesn't care/matter. i have

 

non-EGR block

non-EGR intake & manifold

non-EGR ECU

 

and i still get the EGR check engine light codes. must be body side wiring related or TCU...or......?? no one on here has been able to figure it out. and i don't think there are existing wiring diagrams for the non-EGR OBDII auto's.

 

it's my beater daily driver so while i'd like to fix it, it's not that high priority for a question no one is able to answer or figure out.

 

*** Thanks for posting this - that's helpful to know that you installed a non-EGR auto ECU into the car and it ran fine without a CEL so far. That tells me the ECU isn't really that crucial to all of this. I cut the EGR wire on mine - but somehow it still "think" mine should have EGR apparently.

Edited January 28, 2011 by grossgary

[987687]

99 legacy is Phase I. only 99 Foresters and Impreza RS are Phase II. manual trans are easy to find either way - with or without EGR are common. it's the non-EGR auto trans that are rare.

 

The 2.2 was phase2 in the legacy in 99. Yes, the 2.5 was not, there's one in my driveway.

 

 

Thanks for the clarification on the EGR thing, I didn't know the full details on that.

[idosubaru]

copy i thought you guys were talking all EJ25.

 

good job giving it a try and posting the results here, thanks again.

 

i swapped EJ22 and Ej25 ECU's on mine and noticed no difference at all, now i want to go try again. but mine's a castrated EJ25 to EJ18 and AWD to FWD so not much hope in power gains.