Anyone have any ideas whats going on?

I have a '93 wrx which originally had a U8 ECU which was chipped! (don't know what chip)
The car used to run sweet (at about 290/300 horse)

Then I had a problem with ECU so I changed it for a '94 type ra ECU (which hasn't got a chip socket)

Car runs ok (although bit slower) but every now and again on full boost the engine will cut (varies between 4500rpm and 5500rpm)!!!!!

As the car was originally chipped does this mean that something else on the boost/fuelling side of the engine had been altered which this ECU isn't happy with?

(it's also quite a bit slower starting from cold.......if this helps)

cheers guys!

 

The chip more than likely raised (or removed) the fuel cut level. Ideally you need a boost gauge to see what's going on. There are lseveral reasons for fuel cut. The two that stand out though are the restrictor in your boost vacuum hoses (may need cleaning or re-drilling slightly), or your wastegate not doing what it should be. Check the pre-tension of it, and possibly tighten it up a couple of turns. Might be worth cleaning the wastegate solenoid as well, but that normally presents itself as fluctuating boost rather than fuel cut...

 

On that MY you will want to reduce the hole size in the restrictor 'NOT' increase it, to reduce boost/lileyhood of fuel-cut.

The RA uses a different actuator, so I ecpect the boost control map in you current ECU runs very high duty cycles compared to a U8 and hence does not match the car quite right.

Slackening the actuator by a few turns may help

Basically the ECU you are running is probably the only one that would of done this, as it;s the only ECU I have ever seen that runs high duty. All the others run around the same.

Flog it and get a Z4 ECU.

 

bloody typical!


of all the ecu's a find!

what about if I fit a chip socket and put the chip from the old ecu in this one, do reckon this will cure any problems?

thanks again

 

Fitting the socket should get it running as before. But only run the chip in the socket, do not switch maps i.e fit a switch to the J1 link location.
The 2 ECU use different locations for Knock Correction, hence if you siwtch between maps without an ECU reset it will get in a bit of a pickle.

 

ahh!

so, cut J1 resistor as normal but as long as I don't switch from one to the other I'll be ok?

thats not a problem, I need me ooomphhh back!

thanks again Scott!