Bob Rawle

Changing the ecu will not help a deffective fuel pump controller, the ecu tells it to work at a duty and if the fpc signals back then it will assume its ok but it might not be, have you actually checked what duty its running at on wot. Also 6 bar pressure is way too high, having high pressure means nothing, what flow is the pump rated at for that pressure. You could have 6 bar with virtually no flow.

the afr is dicated from the ecu by what is in the map, on boost the lambda probes do nothing for that. The engine load value is taken from a combination of maf, map and tps plus or minus whatever compensations are active at the time.

The factory std ecu maps provide plenty of fuel for a std car under normal circumstances.

bob

johnfelstead

Listen to Bob, I would check what he is sugesting before going any further. He know his Subaru ECU's / mapping better than anyone i know.

You have to be careful with the MAF wiring because the cables are screened, and if you have a break in them you must replace them with screened cables or you pick up all sorts of nasty interference. Thats why i was asking about if the wires had been damaged.

chrome

*edit.
I'll shut my trap.



bttt

DuncanG

Just saw this on NASIOC http://forums.nasioc.com/forums/showthread.php?t=671294 , maybe its related.

Good luck - sounds like you are due some!

Botswana WRX

Duncan well spotted, I think you may be on to it.
This week I'm off down to Pretoria where the car currently is with my storage scope to see exactly what the injectors are doing - you can't be sure from the ecu read out as that only shows commands to the front end of the injector driver amps not the actual output. Fingers crossed we may find something. Will also look very carefully at the MAF input/wires John and fuel pump controller Bob.
Thanks all, Chris.

Bob Rawle

That thread relates to delayed throttle change onto open loop from closed, without adjustment its quite possible to see a good 1 bar of boost and the ecu still running stoich however it would be trying for stoich not something in between, its easy to map out however it is appreciated that with a unichip you can't change the settings related, it predominantly causes problems on the Eurospec WRx cars although I have seen it on STi's where an exhaust and induction change cause increaesed throttle sensitivity.

good luck finding it

bob

944Turbo

Are you using a high presure pump or a standard one? If the fuel pressure is "far too high" then if its the standard pump could there be a restriction increasing the pressure and reducing the flow.
Not sure where, with what has been changed but it jumped out at me from the posts
Tony

SiHethers

Could it be a problem with the throttle position sensor, so it is never going into open loop fuelling, therefore running lean etc? Check with deltadash or a multimeter would diagnose I expect.

Just a thought

Simon

Botswana WRX

Thanks to all, Bob, and John you're the man. It was the MAF. The new one fitted early on in the saga seems to have exactly the same fault as the original! On the Dyno after checking the pump controller and flow, we tried unplugging the MAF to see if we could eliminate the doubts about fuelling No3. This forces limp mode with preset 'safe' (with standard ecu) fuelling and sure enough we got 11.3 AFR at the 0.5bar limit in that mode. Then tried the third MAF it was fine with everthing behaving as advertised. Then did a careful check of the wiring with a scope and signals to make sure there was no problem there. This because the second MAF works fine on another STi, I still don't understand that. However we could repeat and eliminate the problem by swapping them.
Then put the chip back on and we could map as rich as rich-9.2AFR - just to check we are getting all the fuel needed.
Thanks again guys, Scoobynet is THE net.
Chris

johnfelstead

good news. You can get faulty new MAF's, it's more likely on an MY99/00 than new age car.

I would install an AFR meter on the dash, even if for a temporary period, just to ensure your fuelling is safe on full load. You may have an intermitent boken wire in the MAF wiring, so although its working fine now, it might not in future if this is the case. Basically be a bit on the cautious side for a while.

Buy a copy of delta dash, its a superb piece of software that will help you diagnose problems and will allow you to data log your AFR, MAF voltage etc, so you can do a power run through the gears on the road and then keep those as reference, then compare the readings later on in the engines life to spot any changes.

Botswana WRX

John, what's your recommendation for a good AFR meter?
Chris

johnfelstead

i used to use a lambda link analogue, simple but efective led based display. They do a nice digital lambda meter now too, that has a dial display. You just wire these direct to the OEM sensor via the wiring at the ECU, very simple to install and good enough to show you if your problem returns. Cost about £100 i think.