legacycentral bbs

heya guys i have a 1991 legacy rs and have planted a 1997 wrx redtop engine in
i keept the rs loom and modified a couple of the sensors plugs
now the engine starts fine and revs perfect in nuetral
my problem is when i accelerat i have little power it is like something is restricting it and it feels like there is alot more there but its not being deliverd

I have the ecu from the 1997 wrx and the engine wiring loom

my question is do i need to swap these over and if so is it a straight forward job
will the ecu plug in to the wiring from the dashbord and then the engine loom to the wiring from the fuse box
will the ecu need to be tuned etc

is there any easy option like just getting a ecu chip and a tune etc?

i am a home mechanic and have previously planted a 1996 wrx engine into a 1991 station wagon and was also seemed to lack a little power but not as bad as this conversion infact it was almost unnoticible

i also own a 1996 wrx sti which is my baby but really am a legacy man at heart
my first subaru was a 1989 rs and it was modided slightly and from then on i was in love

thanks for any help
I am almost at the point of pulling the engine and dropping a standard rs engine in to get this car rolling
untill i sort out the issues i need to and tackle the finer problems and drop it back in

Welcome to the BBS Reco.

I would suspect the lack of power is likely due to the difference in engine management, and probably fuel injectors. Do you have a wide band to see if you're running rich or lean?

You likely have two options, get a piggy back or stand alone to tune the 97 engine, or swap to the 97 ECU. Overall, I think swapping to the 97 ECU would be easier in the long run due to not having to mess with tuning. However, it may require some additional sensor wiring to get things working.

thanks josh
no i dont have a wide band i have bare minimal tools lol

so when you say it would be better to use the 97 ecu (which i have)
what do you mean by additional sensors
I have the engine loom from the 97 engine
the engine is currently running on the 91 rs engine loom with a couple mods to it

also do you know if the ecu will be a straight plug out plug in to the wiring in the dash board


the perfect scenario would be i unplug the 91 ecu plug in the 97 ecu then change the engine loom from the 91 to the 97
could it be that easy?

Hi Reco,

Like many things, unfortunately it's not that simple as just unplugging the 91 ECU and plugging in the 97. To use the 97 ECU, you would have to wire in or swap ECU connectors from the 91 to the 97 connectors. You may be able to remove the individual pins from the 91 ECU connector and put them in the 97 if they are the same style pin. However you may run into one that is either too big or too small due to how the ECU connectors are configured. This work would require you to know the ECU pin outs for both ECU's.

When I mention additional sensors, the newer cars have additional sensors for things like fuel temperature and maybe additional emissions controls.

The first step I'd suggest is tracking down the ECU I-O for both ECU's. That would at least give you an idea if any additional sensors would be required.

thanks again josh I havent done anything yet to busy at work but i will give the ecu a go after christmas and will report back with how it goes

Now I have to try track down the I-0 any suggestions where i could find them

thanks again for your help

Hi,
Where RU located?

Do you have a Check Engine Light/CEL/MIL? Sounds like you're in 'limp/fail safe mode' due to the ECU not getting all the info it needs.

In the USA, our cars changed to OBD2 (in '95/96), so the ECU and harnesses changed, BUT some of the sensors, etc. were the same or similar (the MAF sensor was the same on non-turbo Legacy's from '90-99). If yours did not change to OBD2 (or whatever it may be called in your country), it may be easier to swap harnesses....

Check this SITE for ECU info. Should have something you can use.

GL,
TD

Heya TD thanks for the reply

I am located in New Zealand not sure about the obd2 etc

No do not have a engine check light
I do basically know how to get the code to flash if check engine light is on to relate it to the code book

Now you say maybe just a case of changing the harness
do you mean the wiring loom from the fuse box to the engine sensors injectors etc
Or do you mean the wiring harness from the ecu to the fuse box?

I do have the ECU and the wiring loom to go from the fuse box to the engine sensors etc

Now would you possibly know if the ecu from the 91 and the 97 have the same plug inlets things ( so would the 97 ecu just plug in the the wiring that is under the dash? )
I havent been under the dash to look at the 91 ecu plug inlets

Cheers thanks for your time...Reco

Legacy_RS wrote: Now you say maybe just a case of changing the harness
do you mean the wiring loom from the fuse box to the engine sensors injectors etc
Or do you mean the wiring harness from the ecu to the fuse box?

I do have the ECU and the wiring loom to go from the fuse box to the engine sensors etc

Now would you possibly know if the ecu from the 91 and the 97 have the same plug inlets things ( so would the 97 ecu just plug in the the wiring that is under the dash? )
I havent been under the dash to look at the 91 ecu plug inlets

Reco,
Sorry, but I'm not going to be much help w/the wiring. I DO know that in the USA quite a few people have done a complete harness swap from a newer WRX into an older Legacy or Forester, but I don't know what all it entails....I'd look on NASIOC or other sites for a 'How To'.

Also, don't know about the ECU plugs...look online...EBAY UK has ECUs for sale...might find one from a '91 and '97 to compare?

TD