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Old 09-29-2010, 01:29 AM   #1
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Default 2002 WRX ECU on 1999 Miata

Has anyone ever tried or considered using a WRX ECU on a Miata?

You can pick up a WRX ECU for less than $150 on Ebay.
Its designed to support a turbo.
You can access and modify all the ECU maps using Romraider.
You can read and flash the ECU as many times as you like with Ecuflash.
Romraider and Ecuflash are free open source applications and the the only cost is for the Tactrix USB OBDII connector.
Lots of free logging and diagnostic software available.

I was thinking of purchasing a 1999 Miata being sold locally and had an extra WRX ECU and TD04 turbo.

I was looking over the ECU PINOUTs and the only issues I could see were:
Generator needs to be swapped with an internally controlled alternator.
EGR controls need to be worked out or removed.
VICS switch point needs to be triggered somehow (possibly by WRX tumble valve switch)
Ignition coils will need to be converted to 4 coil arrangement.

To make map modifications/cal and tuning life easy I'll likely use a WRX MAF and 440cc fuel injectors.

Seems like it should work but wasn't sure if anyone tackled this in the past.
Am I missing something that needs to be considered?
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Old 09-29-2010, 01:37 AM   #2
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I can't even begin to explain how hard that would be.

Stop dreaming
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Old 09-29-2010, 01:39 AM   #3
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let him dream! lol who knows he could be on to something!
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Old 09-29-2010, 01:42 AM   #4
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Post number 1 and you want to do this craziness. First off, that turbo has nothing to do with that ECU in a miata. If you're gonna go through the trouble of swapping ECU's, go with a DIYPNP. In other words...F that Subaru ECU.
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Old 09-29-2010, 01:47 AM   #5
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Quote:
Originally Posted by thirdgen View Post
Post number 1 and you want to do this craziness. First off, that turbo has nothing to do with that ECU in a miata. If you're gonna go through the trouble of swapping ECU's, go with a DIYPNP. In other words...F that Subaru ECU.
The wrx ecu is awesome.
its so easy and simple to tune, yet works like a charm and can make tremendous power tuned properly.

Problem is, it has NOTHING to do with a miata. I mean literally NOT ONE THING ABOUT IT would be compatible with a miata.


This is either going to
1)cost a ton, be overly complicated, and somehow with pixie dust and black magic he gets it to run the miata (HIGHLY HIGHLY UNLIKELY)
2) He's completely clueless and is having a wet dream and is FOS
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Old 09-29-2010, 01:51 AM   #6
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Quote:
Originally Posted by 18psi View Post
The wrx ecu is awesome.
its so easy and simple to tune, yet works like a charm and can make tremendous power tuned properly.

Problem is, it has NOTHING to do with a miata. I mean literally NOT ONE THING ABOUT IT would be compatible with a miata.


This is either going to
1)cost a ton, be overly complicated, and somehow with pixie dust and black magic he gets it to run the miata (HIGHLY HIGHLY UNLIKELY)
2) He's completely clueless and is having a wet dream and is FOS
he knows more than i know! i didnt understand half of what i read in the original post!

WRX ecu on a miata this might work possible cheap solution
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Old 09-29-2010, 01:53 AM   #7
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LOL
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Old 09-29-2010, 02:43 AM   #8
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It would be involved no doubt.
But aside from the cam/crank signal, probably not that much different to building an MS and creating a patch harness when you think about it.

The coolant and air temp sensors would need swapping to WRX ones.
WRX runs high imp injectors (almost plug and play int a Miata).

The tricky part would be the RPM.
You would need to have a suitable RPM rignal to be read from the engine, this is done on the Miata via the Crank sensor in conjuction with a Cam sensor in the 99 models. The signals they send out are not the same as the Subaru ones, this would need to be addressed,whether you use the subaru units on the Mazda engine, or somehow get the subaru software to recognise the Miata triggers.

Honda ECUs are in the same boat as WRX ones (can be reprogrammed) and run a cas, still not any easier to integrate into another car though.

For Miatas, time and money is best invested in the MS as others have said.

But yours may be a little different
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Old 09-29-2010, 02:52 AM   #9
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Dude, the firing intervals on an inline 4 and a flat 4 are not the same.
You migth as well just retrofit a honda dizzy onto the engine and use a chipped honda ECU. That would likely be a better ECU and it would actually WORK.
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Old 09-29-2010, 09:00 AM   #10
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Quote:
Originally Posted by WonTon View Post
WRX ecu on a miata this might work possible cheap solution
This was a freakin awesome laugh - thanks for making my day lol
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Old 09-29-2010, 09:19 AM   #11
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do it and report the results.
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Old 09-29-2010, 11:16 AM   #12
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Quote:
Originally Posted by Full_Tilt_Boogie View Post
Dude, the firing intervals on an inline 4 and a flat 4 are not the same.
You migth as well just retrofit a honda dizzy onto the engine and use a chipped honda ECU. That would likely be a better ECU and it would actually WORK.
I don't believe there is anything funny about the timing intervals on a Subaru. As someone else stated, the trigger pattern is different, but the ECU doesn't care if it's Flat, V, or I. The factory WRX computer does pull one or two degrees from one of the rear cylinders in some years, but it's a heat/knock issue, not a mechanical thing. I've also heard of people using DSM ECU's as cheap standalones before MS was available. They even have a Group-N program for the early US ECU's to make them speed density.

It took me all winter to get my Autronic harness made, debugged, and the ECU programmed. The process would be similar. Tedious, but doable.
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Old 09-29-2010, 11:18 AM   #13
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the DSM shares the same CAS pattern as the miata and the motors are more in common.


both are a waste of time and money.
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Old 09-29-2010, 11:42 AM   #14
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I remember back when I had lots of time and no money. I would have tried something like that if I already had the parts and a spare car to **** with.

That weird crank sensor is going to be a bitch though. I think the easiest solution would be to design a crank wheel, and find somebody with a CNC cutter, or see if you can carve up a '99+ wheel to spec. Might even be able to grab one of those 60-tooth wheels and remove the teeth you don't need.
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Old 09-29-2010, 12:20 PM   #15
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or build a DIYPNP for around $450 and load the basemap and enjoy a fully programmable ECU that works out of the box?
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Old 09-29-2010, 12:42 PM   #16
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Hey guyz I'm going to install a v4 from a honda motorcycle into the back of my miata.

Its a great engine, has good midrange torque and tons of topend power, and I can get one at a junk yard for 200 bux. I'll just mount it in my trunk and make the miata a RR by sprinkling pixie dust on it and masterbating furiously onto the wiring and mounts
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Old 09-29-2010, 12:42 PM   #17
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$450 is still a heck of a lot more expensive than free. Besides, I'd be a LOT stupider now if I didn't spend my years making things work in ways they weren't supposed to. Now I'm old and lazy and can buy my way out of problems.
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Old 09-29-2010, 12:49 PM   #18
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it sure as **** wouldn't be "free" to get that thing to work. if its even possible.

unless you ignore all the sensors needed, wiring, plugs, soldering equipment, and TONS and tons of time.
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Old 09-29-2010, 01:09 PM   #19
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Okay, then build a v3.0 MS-II.

$247.00 for the kit, $20 for the extra parts needed for the cam/crank inputs, ebc, idle & alternator reg. mods, around $20 to build a harness, and about 4-5 hours of time. You could have it built, installed, and tuned in one weekend; I'm sorry but that's cheap and easy.

I'd rather do this, spend a little extra cash up front and have a platform that is supported, has a big user base, and painless than to have to source random parts, hope i get good deals and then employ the pull and pray method.

I can't believe how cheap miata owners are sometimes, even when we acutally have a relatively cheap options for a pretty great ECU solution. Next you'll be trying to figure out how to install adjustable coliovers from a civic that are even cheaper than the $200 shipped racelands.

In the least to make the WRX ECU work, off the top of my head, you need the following:

Somehow mount WRX Cam/Crank sensors $$$$$
Somehow mount the correct trigger wheel patterns $$$$$
WRX AIT sensor/ CLT sensor unless you can reprogram the curves $$$$$
WRX idle valve $$$$$$
C.O.P. upgrade $$$$$
Alter the injection harness to change the WRX 1-3-2-4 firing order to the miata 1-3-4-2 order.

Last edited by Braineack; 09-29-2010 at 01:19 PM.
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Old 09-29-2010, 01:10 PM   #20
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I'm not saying it's a good idea...

The guy said that he already had the ECU. He just needs to figure out the triggers, figure out possible dwell issues, get a handfull of common sensors, and find an ECU connector to adapt the harness.

I have in my possession a hand made digital dash constructed by the previous owner of the standalone in my DSM. It was created in the mid-90's. It reads the serial stream from the computer with a microcontroller, plus two add-on temp and pressure senders, then displays the readings on a dot matrix LCD screen, it has 3 buttons, two of which don't seem to do anything. Anyway, the two boards were hand drawn and etched, the interconnects are old computer ribbon cables that are cut into sections. It was all assembled into what appears to be an old modem housing. The same guy also built a device based on a flip-flop that allows a 2-channel ignition to work with an ancient 1-cannel J&S Safeguard. I doubt it cost him much to build, but I'm sure he spent months on it.
Most people just like talking about this stuff to try and sound smart, but some people actually do it.
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