Anyone know whether an ECU Reset is either effective or neccesary on a 99MY Scooby?

I know they have a new ECU, and have heard that it learns about better fuel as well as protecting against pre-ignition due to lower octanes.

I have been trying different fuels prompted by comments on the BBS, and the car is certainly smoother on SUL. The question is, will it be (even) quicker after a reset?

If not, I can save myself the bother of resetting all the radio channels!

Bye....

SUL fuel is alot more expensive than 95 RON unleaded, does the increase in performance warrant the increase in cost. ?

How do you reset the ECU yourself anyway ?

If you disconnect the battery for more than 30 minutes it should clear what the cpu has learned (allegedly) this is still a cause for major debate though. Once it has been drained you then have to run at near full boost for 30 seconds or as long as you can, which on the road would be unlikely, unless you know 4 huge rugby players and live near a long steep hill http://bbs.sidc.co.uk/smile.gif this should allow the ecu to learn the new settings. You should have also run on about 3 tanks of SUL before doing this to ensure you have only SUL in the tank.

Got no reply to my specific question about ECU resets on 99 cars, so tried it anyway yesterday.

As far as I can tell, it made no difference. The car was running beautifully on SUL anyway, and continued to do so after the reset.
I had previously run it on 95 RON and it seems to improve by itself after a while when changing to SUL.

So unless anyone can tell me different, 99MY ECU's are self-resetting!!!

Tony

Without a rolling road you'll never know for sure, but when I did mine there now "seems" to be more power above 4000

this was after a change to SUL and a battery disconnect for an hour.

could just be the effect of a good thrash with SUL ?

Surely someone must be able to find out for sure what the position is with this reset ? Doesn't anyone have any Jap mates ?

The engine management system on these cars seems very similar to the Bosch motronic system. All the same functions are monitored and the turbo boost is controlled in exactly the same way. So, lets assume that the Subara ecu is a rip off of the Bosch system. There are a set of default values in the ecu. When power is removed it reverts to using these "average" settings. As each car is different a system of "adaptive learning " is used so that the ecu optimises itself by fine tuning itself. It then stores and uses these values as long as power is maintained. The knock sensor is used to keep the timing advanced as much as possible dependant on fuel quality. If low grade fuel is used the the ecu will sense knock and retard the ignition. If this is not found to eliminate the knock then it will then reduce boost pressure. Once the condition is stabilised it then attempts to restore the advance slowly until it finds the knock point and then it backs off again. In this way the engine is always run at the highest level of power for the fuel grade and temperature conditions. It necessarily follows that disconnecting the power after filling with SUL will then force the ecu to use default settings. As the car is driven the SUL will allow much more advance to be run and the boost will not need to be reduced. That's why the car feels better after the "reset" There is absolutely no need at all to run it at boost for a period of time to teach it settings. It will always use the highest optimum boost and most advanced ignition settings that it can. Just changing to SUL will allow the ecu to start to advance ignition settings as it will not be knocking.
The mass airflow meter, temp sensors, lambda sensors, air temp sensors, etc are all used in conjunction with the knock sensor to this end.

Guess I've gone on a bit but I've read so many postings about the "mythical" reset that I thought I would put my point of view. I have studied the Motronic system to a high degree of detail and would welcome any comments/feedback on this anyone would care to give. I have the Bosch reference books available if needed.

Bob

[This message has been edited by Bob Rawle (edited 04-05-99).]

Put a (full, empty to brimmed) tank of SUL in my MY99 (no mods) for the first time this week (4000 miles done so far on NUL), and within 50 miles noticed an improvement in "smoothness" and response. No ECU reset done, so I figure the ECU does it's job properly.

I'll give it a few more tanks of SUL , then change back to NUL and see what happens.

Rob.

The only benefit i can see from all the discussion is that the reset makes the car re-evaluate the fuel setting etc immediately rather than having to wait for it to resample properly.

Bob,

The way you put it, it sounds like the system is always "hunting" (advancing the ignition timing to some extent, finding the knock point then backing off a bit) -- have I got that right?

-= mike =-

PS. Not that I'm suggesting there's anything wrong with this, just trying to check if I understood correctly.

This is the way that the Motronic system works. The ecu always seeks for the most optimum ignition setting.I found it noticeable within a very few miles when changing from UL to SUL in the Cav.

Bob

This is the way that the Motronic system works. The ecu always seeks for the most optimum ignition setting.I found it noticeable within a very few miles when changing from UL to SUL in the Cav. The Motronic system is actually capable of advancing and retarding the ignition for each individual cylinder independantly thus compensating for wear.

Bob

Again I ask..

is it not possible for one of the rollingroad owners to find out for sure
i.e. test with NUL, test with SUL, then test with a reset ?

'twould be nice to iron this one out once and for all.