Facinated by my new found understanding (very basic!)of the ECU, I attempted an ECU reset on my STI Ver 5 Type R last night by unplugging the battery overnight.

To my disappointment, I an now running a max boost of 0.95 bar compared to 1.1 bar in 5th. In 1st and 2nd, I now run about 0.75 boost compared to 0.9.

I find this rather strange and . I hope someone could shed some light into this. Is the STI tuned ECU auto-tuning, like the Lambda auto-tuning option on the Possum link?

PS: I did not trash the car after reset, and only done about 30 miles.


[This message has been edited by Seraph (edited 18-09-1999).]

 

Could just be poorer quality fuel? - try filling with high qual SUL (shell?) and putting octane booster in to lift to 100 then reset. (only a guess-timate, but have heard it done before and its worked!)

 

I believe the latest "offering" on the fabled reset (may only apply to 99/V cars) is that eventually the ECU will adapt itself, but a reset may speed this up. Tends to work best after something dire has happened eg use of supermarket fuels !

 

I am alreadly using 100 octane fuel! Does the ECU automatically re-tune itself, in terms for A/F ratio, boost, timing advance etc?

Do I need to take the car for a hard drive before the ECU will increase boost levels?

[This message has been edited by Seraph (edited 18-09-1999).]

 

Hi there,

A lot of people say that after a reset you have to take the car for a "drive", where you obtain maximum boost. They say dont "boost" the car until you can obtain the maximum pressure.

ie - drive it gently until you have a straight uphill road (or a few people in the back). Its normally best to do this in third gear from about 3000 revs upwards...try and hold the boost for a few seconds.

I dont know if this is true..or if it relates to your engine. Its worth a try...

Cheers,

J.

 

All that has happened is that by disconnecting the battery you have forced the ecu to use its default values. The car had obviously adapted itself to the higher fuel ron before you did it and will have to re-learn all over again. This is basically the point about this. The ecu reset does not exist, all that happens is that you force the ecu back to basics and then it learns again. If the car was at optimum before the "reset" then no benefit (or worse performance) will be seen. If a car has been running on poor fuel and has then been filled with good quality fuel it will speed up the transition but it will still adapt itself.

The ecu is adapting all the time. After the "reset" about 30 miles of mixed driving will get it on its way but the myth that you need to thrash the poor thing to get decent boost is just that ... a myth. Your boost will improve as it learns, be patient and don't reset it again !! Its obviously fine.

Bob

 

does the same thing apply to UK spec MY99s?

 

I believe it does. Anyway people are always going to argue over this topic.
Try it..if you run more boost after a reset then great, if not but after a while the ECU adapts then great.

Can do no harm and you can make your own judgements.

 

Quick update... I have just completed 50 miles since reset. I noticed that the boost is still a little lower but during cold weather (night driving 23 Deg C), I am now doing 1.05 bar boost in 5th.

It does not seem that the ECU reset has done anything to the tuning, just that I first drove it during hot afternoon (28-30 Deg C).

Tuners (e.g. PE, BPM etc), in all your experience, does the factory ECU self-learn and adapt to petrol, driving characteristics etc?

It would be good to get a technical input to the fabled ECU reset!

 

Pat,

... Or you switch back to standard fuels and don't want the engine to damage itself in the process of learning how much retardation it requires!

Moray

 

Seraph - Re-read Bob's posting. His conclusions are the same as mine. (And don't necessarily expect the best technical information to come from "tuners". The best tuners will admit they're learning more all the time and indeed, often a good proportion of their knowledge comes from enthusiast "amateurs". Others will pretend to know what they're talking about yet in fact be talking bxxxxxxs.)

 

Colin, I agree. But what I was interested is how the Std ECU learns? I thought the programme is stored in Read-only memory. Also, what sensors does it utilise and what parameters is the learning based on?

Some enlightment would be good.

 

It's almost impossible to get a microcontroller based system to work without some RAM. It's therefore quite likely that there is some RAM in the ECU. A simple way to tune on the fly is to copy the ROM image into RAM on boot (which improves access time too!). Another method using less RAM would be to maintain a small array in RAM which contains "adjustments" to the ROM image.

I believe that the Subaru ECU is somewhat less "dynamic" than the Toyota ones (these always run the engine on the limit of knock, adjusting advance about 10 times per second) but will still retard the timing (pretty rapidly!) on detecting knock. I believe that the Scooby ECU will advance the timing again (slowly) probably until it runs into knock and then back off a little bit again.

To speed up the advance, you can reset the ECU to factory spec. Of course if you have been running wonderfuel (say 130RON aviation fuel) then your ECU will have advanced the timing quite a bit beyond factory spec (albeit slowly) so resetting is a Bad Idea(TM) unless you want to wait for it to go like a rocket again :-)

Cheers,

Pat.