Diablo

Mine's been reset by the dealer twice during servicing and warranty work and both times the car has performed worse afterwards.

If your car is running like a dog on crap fuel, and you're going to use 97 or better, then it may well work.

All depends on whether or not default settings are better or worse than current.

D

Nir

I was wondering whether changes in turbo boost pressure, according to gas quality, are really possible.
(as described in

pat

Nir,

you are correct in stating that boost pressure is mechanically regulated, ultimately at least. The wastegate actuator will open the turbine bypass valve when pressurised to about 7psi... of course the cars run more than this. The way this is achieved is by having a wastegate actuator control solenoid. This is either a 2 or three port device. In essence, it bleeds pressure away from the actuator, making it "see" less pressur. So by bleeding, say, 7psi the turbo output pressure will actually be 14psi.

The control solenoid is controlled by the ECU; hence the ECU can govern the boost pressure to an extent. It cannot, however, regulate total boost to less than 7psi.

When using poor quality fuel, there is a higher tendency for the engine to knock. This can be dealt with in many ways. The easiest solutions are to back off on the ignition timing, and to reduce the boost pressure. Of course both will result in a power loss. Perhaps a better, if slightly more expensive, approach would be to control charge, oil and coolant temperature, so that the tendency to knock is reduced, allowing the same level of boost and advance, and perhaps a bit more power as a bonus :-)

But these aren't cheap options, so for road cars a compromise is used. The JECS ECU on most Subaru cars (pre- Phase II engine, at least) does use ignition retardation to control knock (now wouldn't it be nice if the JECS could control the IC water spray?). Rumour has it that it's quick to back off, but slow to advance again, hence resetting the ECU after a period on poor fuel will get it back to "normal" much quicker.

The Subaru ECU is reputed to be much slower than, say the Toyota 3SGTE unit which adjusts (advances or retards) ignition timing 10 times per second to run it on borderline knock.... ie enough to be detectable but not to do any damage even after prolonged exposure.

Hope this helps,

Pat.

Trout

iTrader: (1)

Another comment regarding ECU reset.

There have been a number of drivers who have tried one of the number of ways to reset the ECU only to complain that it did not work.

ECU reset is believed to imbue the car with some magical quality that will make it instantly better.

This is not the case - the ECU has worked over a period of time to adjust timing, boost, ignition, etc to the fuel that you are using and the way that the car is driven (only inasmuch as this changes the ambient operating parameters of the car - e.g. lots of town driving it gets very hot).

Having learned how the ECU should work in your specific case, you then reset it and the car runs like a dog for while. This is especially true of imports relearning 97RON fuel.

So, you can wipe the memory from your ECU - but it is not the magical performance panacea it is laid out to be.

R

Nir

Thanks for the info

My ECU is currently Superchips one.
- How can I know whether reset is needed (could it be that, alternatively, the ECU tries to increase the boost from time to time?)

- How can I know whether it is needed to drive like mad after resetting?
I've performed reset two times after filling good fuel and it worked (without driving fast afterwards)

- Unfortunately I will have to use reset on a regular basis because even the 98 RON fuel I buy isn't constantly good. But I'd prefer not to disconnect the ECU everytime because the electrical connectors may become loose

Nir

GavinP

But the ECU is compensating for the poor fuel.

Say for arguments sake, that you have a tank-full of poor quality fuel and you then reset the ECU - what happens ?

The ECU starts the car on the default settings and could potentially cause damage to the engine.....

Thanks

Gavin

Trout

iTrader: (1)

Why are you disconnecting the ECU every time?

Check out MRTs page they give you instructions on how to do it properly.

But I can't see what he gain is from constantly resetting. The ECU will take time to learn the new fuel and by that time you will reset again.

R

Nir

Because the fuel quality in the gas station is not constant.

N

Nir

No, the thing is like that:
When I'm running out of fuel I go to the gas
station and fill partial tank.
If it's poor, I feel it immediately.
The engine becomes weaker and G-Force is not
noticeable.
I *do not* reset the ECU for *this* tank.
After I empty the poor tank, I fill another
tank, hoping it is better.
Then, I reset the ECU.
If I wouldn't have, the settings would
have remain for the previous, poor quality,
fuel.
Usually the chances for good/bad quality fuel
are dependant in the specific station, I am
still researching which stations are the best.

N