legacycentral bbs

I've been wondering about this for a while. A lot of us want a better ECU, but pretty much we only have aftermarket standalones to go with. So why don't we just rewire our ecu connectors to use a newer ECU, like say a US WRX ecu? Yes you'd have to change some sensors here and there, but other than that it should work right? Might get a CEL for only having one O2 sensor, but that can be fixed with some resistors or actually installing a second sensor. What am I not understanding about doing it this way? This would open up the aftermarket to many ECU upgrades, mostly piggybacks.

After looking at the ECU pinouts it appears an EJ22T harness uses 66 pins, and an 02 WRX harness uses 95 pins (assuming both are auto, manuals use 5 less), so one would have to add 29 or 24 pins to the harness if I counted correctly. Personally I think this could be easily done by grabbing a bunch of ECU connectors from the junk yard and splicing together a patch harness. Does this even seem plausable?

It would seem that most of what needs to be added is stuff like the fuel related items, and the tgv wiring. It seems one could keep most of the sensors, but a few use different voltages.

What am I missing here?

Well, WRX ecu's aren't exactly cheap from what I've seen, and they're more expensive to tune than standalones or piggybacks

Building an adaptor harness is far from a trivial task. 66 pins is a lot. The additional sensors are also a lot of work to install and wire.

Im sure it could be done. It'd probably be easier to swap in a WRX wiring harness though, which is a lot of work.

I think a piggyback, like a PP6 is a much better solution. Its not that much wiring, its easy to tune once its in, and they can be had for about the same price Ive seen WRX ecu's going for.

I'm going to have to argue this, not because I want to be a dick, but because it's good for discussion.

You're not installing 66 pins, you're adjusting 66 pins and installing 29 or 24 more pins.

It would be hell of more work to put in a WRX harness.

How much wiring do you need to splice for the perfect power? They seem to go for like $440 from rallitek, WRX ECU's normally go for around $200 on nabisco, and I'm sure you could find a cheaper deal somewhere.

Again, not trying to be a dick, just trying to continue the converstation.

OMG HOW DARE YOU CHALLENGE MY ALL-KNOWING PROWESS OF THIS SUBJECT!!!!!


Anyway

Youd have to do every one of those 66 pins because I really doubt they have the same locations and functions on both ECUs


Plus the MAF, pressure sensor, and I believe the knock sensors are also different

So to do the swap you'd need:

WRX ECU, oxygen sensor, MAF, pressure sensor, possibly the intake manifold (I think the ECU requires a reading from the EGR system), and therefore the heads, various small bits of machining (second O2 bung), and all the associated wiring for the above

I'd peg the cost for all that at around $700, it could probably be done for less if you've got the tools to do the machining, and if you get lucky on nasioc

It'd be a lot more if you wanted to bite the bullet and get new O2 sensors and MAF instead of used.

After all that you're still left with the lack of tunability without expensive equiptment. If your goal is in the 220-240chp change, it's probably fine. But that can be done with the stock legacy ECU.

Great question!

One of the long-term things I'm thinking about is swapping the EJ22T into a GC. People fear swapping into the later 90's ones because of OBD II, but I'm wondering about using a WRX ECU, heads, intake manifold, etc...

You can certainly do it. You just have to make the ECU think it's on a WRX, so you have to do the stuff Splinter's saying, and some more:

Don't forget the cam and crank angle sensors, for example. WRXes use completely different pip patterns on the sprockets.

Something has to pacify the TGV stuff too... I don't think simple resistors and whatnot will suffice.

You also have to add some stuff for fuel tank pressure and level sensing, and maybe power steering pressure sensing. Again, I don't know if you can use simple passive components here.

Reverse the TPS.

See if the IAC valve is compatible or not.

It all depends on how much work you're willing to do...

Yeah, basically the WRX ECU conversion sounds involved - basically you need to build a WRX engine compartment and just drop the EJ22T short block in the middle of it. But, if you already had a goal of DOHC heads, they are almost identical projects anyway.

Does this information below and the two categories sound about right?

Things that would probably "come along for the ride" easily in a head/intake manifold/turbo/intake conversion anyway:
* cam angle sensor
* TGV or or some kind of delete
* TPS
* IAC
* MAF
* MAP

Added work just to make the WRX ECU happy
* crank angle sensor (maybe not necessary?)
* fuel tank sensors (maybe not necessary?)
* fuel pump (many people already have Walbro WRX pumps anyway)
* power steering pressure sensors (trickable?)
* O2 sensor (not a big deal if you already have WRX exhaust like me)
* knock sensor

That's a pretty good way to look at it, if you're using WRX heads.

I think the WRX MAP sensor fits on the intake manifold.

The WRX MAF sensor won't fit the stock intake plumbing, so you'd need a WRX airbox too.

Hopefully you get the harness with the heads.

Not sure if you're meaning fuel tank sensors as the fuel controller....but I believe the WRX does not have a fuel pressure regulator, but rather has a fuel controller that varies pump pressure.

I will add the PP6 is not the smoking bullet fix for all our ECU tuning problems. It has problems of its own, and while a lot of us have had intermittant issues, no one has been able to narrow down to the specific problem. Because of this, I can't see it as a viable long term solution.

The WRX does still have an FPR.

It just also has a fuel pump computer that reduces voltage to the pump when engine load is low. I guess that reduces cabin noise and increases pump longevity.

The WRX ECU has some sensors and solenoids that have to do with the evaporative emissions control system. They let it test that the fuel tank holds pressure/vacuum and stuff like that.

Splinter wrote: OMG HOW DARE YOU CHALLENGE MY ALL-KNOWING PROWESS OF THIS SUBJECT!!!!!

I can't think of a witty come-back

Youd have to do every one of those 66 pins because I really doubt they have the same locations and functions on both ECUs

I was actually thinking of grabbing another EVO patch harness, and a WRX/STi patch harness and splicing them together, probably the easiest way (most expensive too)

Plus the MAF, pressure sensor, and I believe the knock sensors are also different

So to do the swap you'd need:

WRX ECU, oxygen sensor, MAF, pressure sensor, possibly the intake manifold (I think the ECU requires a reading from the EGR system), and therefore the heads, various small bits of machining (second O2 bung), and all the associated wiring for the above

I'd peg the cost for all that at around $700, it could probably be done for less if you've got the tools to do the machining, and if you get lucky on nasioc

It'd be a lot more if you wanted to bite the bullet and get new O2 sensors and MAF instead of used.

I see the different MAFS as a good thing, we all know the Hitachi sensor has its limits, and yes the Denso sensor has its limits too, but they're higher.

The knock sensors are slightly different, and send a slightly different signal, rewiring them isn't hard though, might even be able to get away with just using the stock one.

WRX's don't have EGR, lots of the new gen engines don't have EGR actually.

After all that you're still left with the lack of tunability without expensive equiptment. If your goal is in the 220-240chp change, it's probably fine. But that can be done with the stock legacy ECU.

My goal isn't to make huge power, it's to expand my aftermarket of ECU choices.

vrg3 wrote:You can certainly do it. You just have to make the ECU think it's on a WRX, so you have to do the stuff Splinter's saying, and some more:

Don't forget the cam and crank angle sensors, for example. WRXes use completely different pip patterns on the sprockets.

I had forgotten about that, the WRX uses a 30 tooth sprocket I think versus our 6 tooth. that'd definately have to be changed, along with the sensor as I don't think it can react quickly enough to pick up 30 teeth per rev.[/quote]

Something has to pacify the TGV stuff too... I don't think simple resistors and whatnot will suffice.

Yeah, I dunno for sure if resistors will work, but the TGV's are closed when coolant is cold and open when it warms up and the engine has been on long enough. I believe it just sends a 5v signal to the motor to open it, and verifies this through the sensor on the other side, other than that it's 0v the whole time. Or maybe that's backwards. Either way I'm sure it could be solved with some wiring. I wonder what Impreza guys do when they remove the TGV's.

You also have to add some stuff for fuel tank pressure and level sensing, and maybe power steering pressure sensing. Again, I don't know if you can use simple passive components here.

Reverse the TPS.

See if the IAC valve is compatible or not.

It all depends on how much work you're willing to do...

The fuel stuff, I'm wondering if one could use the stock canister and stuff, and just add the other stuff to the tank, but I haven't looked into what all comes on the canister that goes in the rear near the tank.

I don't know about the PS switch, I think it just grounds the switch at some rpm or something. And I don't believe it verifies this through any real way.

If the IAC valve wont work, I think it would be easiest to just use a WRX throttle body, as that comes with the TPS, IAC valve, and MAPS.

rallysam wrote:Yeah, basically the WRX ECU conversion sounds involved - basically you need to build a WRX engine compartment and just drop the EJ22T short block in the middle of it. But, if you already had a goal of DOHC heads, they are almost identical projects anyway.

Why do you need to be DOHC, can't you just use a DOHC sprocket so the sensor works properly?

Does this information below and the two categories sound about right?

Things that would probably "come along for the ride" easily in a head/intake manifold/turbo/intake conversion anyway:
* cam angle sensor
* TGV or or some kind of delete
* TPS
* IAC
* MAF
* MAP
* EGR

Added work just to make the WRX ECU happy
* crank angle sensor
* fuel tank sensors
* power steering pressure sensors
* O2 sensor (not a big deal if you already have WRX exhaust like me)
* knock sensor

I don't think you'll need to change the cam sensor, but the crank almost definately.

No EGR as mentioned above.

the rest also mentioned above.

vrg3 wrote:The WRX MAF sensor won't fit the stock intake plumbing, so you'd need a WRX airbox too.

I think there are newer air boxes that use a standard bolt-on MAFS housing with the same denso sensor, so maybe this is a viable option.

That was kind a long reply.

So yeah, I think I might have to try this.

For the TGV's, I think you can remove the CEL using ECUTEK. Otherwise, you have to find a way to bolt the motor to the sensor, so that the ECU sees the proper feedback. I think APS mass produces such a coupler.

For the PS, i think it signals the ECU to raise the idle when necessary (ie full lock). I'm not sure if it'll throw a code to leave it disconnected though.

Haha, wow that WAS a long reply!

Actually, I'm not saying you need to go DOHC. I'm saying that DOHC is a separate goal many people already have anyway since it is supposedly the secret to real power. So, I'm looking at the overlapping work between the two projects to see what kind of bonus there is.

You can see that the overlap is a big portion of the work. "50% bonus savings". That's what I'll tell the (soon-to-be) wife when I try to sell this plan some day.

PS - I edited my posts above to match your comments THAWA

Some nabisco searching.

Certain aftermarket ECU's can "turn off" CEL's, meaning they wont throw the code even if the conditions for the code are met:
http://forums.nasioc.com/forums/showthread.php?t=997126

mikec is quicker than me!

The problem with this is (which will include some opinion): You do all of this work and spend all of that money to have a really finicky OBD-II ECU that will complain about everything. People with properly running OBD-II cars want to throw their ECU out the window sometimes. And on top of that, if you want to do engine management after it is all installed... you will end up paying just as much as going stand-alone to begin with.

I thing going stand-alone and getting plenty of tuning time is a better route. That eliminates the MAF problem, too, instead of just momentarily loosening the noose IF you get the new one to work.

I agree with you. If you're looking at this from a cost standpoint, this probably isn't the best way to do it.

If you have a bunch of parts laying about then why not try it, right?

I think the ECU is a step above, it has very good diagnostic features, and allows you access to OBDII as you said which has advantages in itself.

^ That is true.

I've worked with the Hydra system, and while it is an impressive piece of hardware, you're left to figure stuff out for yourself when it doesn't run properly. From what I've been able to figure out, the only time you'll see a CEL out of it is if it detects knocking.

Yeah, It's so easy to diagnose an OBD-II car, they keep track of everything. What I really like is that for most sensors and whatnot, it can tell you whether there is a damaged wire or the sensor is bad. Rather than just getting a code for the sensor, and having to figure out if it's still got continuity and voltage etc.

Brat4by4 wrote: I thing going stand-alone and getting plenty of tuning time is a better route.

Maybe in one of these old SS's. But, what I don'd understand is that if you were working in a post OBD-II chasis, how do you keep the car street legal with a stand alone? In MD, they're going to try to plug into that OBDII port every year.

THAWA, did you ever go through with this?

The local performance shop is recommending me to do a WRX harness swap in order to open up tuning options

Seems like a silly idea to me, why not just get a used LinkPlus for like $500 off nasioc and wire it in? It's going to cost that much to get the WRX ecu in and working, and then when you're done you STILL have to reflash it or buy a UTEC or something to tune it.

I mean if you already have WRX parts, or you're dropping in a WRX motor, it's not a terrible idea, but if you are starting from scratch...

PS splinter give me your MAF.

Rocket said that the WRX harness swap they did took them a day. THe idea isnt to take a WRX ecu and plug that in, but to take an Autronic or Link plugin ECU and use that.

The issue with a wire-in Autronic or Link is that you then have to start from scratch with a fuel map, fan relays, idle control, and all those other goodies.

Whereas if you get a WRX intake manifold and harness, you can swap over the relevant sensors, and just plug in the new ECU.



What happens with my MAF depends on what happens with my engine management predictament.

Ohh, just the harness swap. Gotcha.

I'm not certain, but they are probably talking about their shop rally legacy which actually has a WRX motor in it, might be a bit more hassle hooking up the old ej22.

No, they said they did it on 2 EJ22T's