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Old 05-18-2000, 03:26 PM   #1
Aaron'z 2.5RS
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Member#: 1026
Join Date: Mar 2000
Chapter/Region: MWSOC
Location: Hickigan
Vehicle:
'00 RS/WRX Stg5
'98 RS Stock

Question Possible ECU reset REVISION

Hi all,
I have been resetting my ECU (MY99)for some time now using the known method.

Well i reaciently took my service manager and lead tech from my dealer out for a ride, trying to figure out why the dam thing keeps hesitating.
I explaned to the tech bout how i reset the ECU and he sed that letting it idle doesen't seem logical to him.....let me explane.

He sed that letting the car idle after draining the memory cap (ECU memory) would not allow the ECU to account for hard running conditions.
This makes sense to me. If letting the car idle "base lines" the ECU. It doesen't have a chance to "learn" any of the "hard running" conditions. I.E. WOT, knock sensor readings, O2 sensor readings...and many more i'm sure.

The tech sed "he" would start the car after reconnecting the batt and take off driving, trying to run it at as many different conditions as possible. i.e. WOT, high RPM, ect, ect, ect.
Seems to make sense, BUT, alass after about a week the car is STILL hesitating.
So, i donno.....ya'll make the call.....
AaRoN
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Old 05-18-2000, 03:32 PM   #2
BoomerRS
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Member#: 1271
Join Date: Apr 2000
Location: W Hartford, CT USA
Vehicle:
98 RS
****in Rally Blue

Post

Interesting... I just reset my ECU after putting in an Amsoil and I was thinking the same thing... the car is not learning much just sitting there idling. But I guess it will as soon as you start driving again. I doubt it matters much either way since the ECU should always be making adjustments.
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Old 05-18-2000, 04:20 PM   #3
uktena
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Member#: 1267
Join Date: Apr 2000
Location: Charlotte, NC USA
Post

From my limited understanding of the ECU; it has a base program (like the BIOS in a PC) that will provide some baseline info. The part about "learning" baseline info is correct and you definitly want to "teach" the ECU spirited driving lessons. I have had very good success using the previous described method of disconnect, idle till warm; but then shutting the car off a coulpe of minites then going for a performance "teaching" run. (full throttle, redline in each gear)
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Old 05-18-2000, 05:19 PM   #4
svxtrem
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Member#: 1008
Join Date: Mar 2000
Location: Grand Forks, ND
Vehicle:
2006 STI
Steel Grey Metallic

Post

Right. The car has a baseline 'map' that controls fuel and timing related to MAF/RPM/TPS settings. It 'learns' the fuel map while driving in warmed up in closed-loop mode. The o2 sensor provides it with feedback to optimize the fuel ratio. It measures the its base map against what the o2 sensors say and builds in correction coefficents to the map to achieve a stoichiometric fuel ratio. Therefore, for fuel, to learn, it needs a nice long cruise when warmed up. For spark timing, it uses a base map. The feedback for this is the knock sensor. It will NOT 'probe' for detonation so as to advance the timing. Timing is set in the map period. The only thing it will do is to retard the timing when it senses knock. It has an a square algorithm where it pulls back timing in progressively larger increments as knock continues. It then creates a correction coefficent for spark timing in that cell (about 400 rpm). That's why you can get flat spots in the engine. Whether you hear detonation or not, the ECU thinks it hears it. The spark maps gradually return to normal based on time or distance, I don't know which. The motronic actually measures distance and figures that after you've run the contents of about a tank of gas, that it will revert on the next start up to the base timing map. Other ECUs have other strategies. Based on my experience with a '99 it would seem to measure a certain distance (I would guess about 300 miles) before it sets the cell back to norm. Anyways, hope this helps, and also sts the stage to clear up any BS about driving special to 'learn' driving habits.
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