ECU reset - interesting results
Thread Starter
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Joined: Feb 2001
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From: You wish
Wow, a lot of speculation.
First, let me tell you what happened when I did the reset again with the airbox lid on. First of all, it didn't stall on me. Second, the hand timed performance was much better (compared to before with the airbox lid on).
Marcucci, I don't know if it was me who recommended that to you, but I don't advocate frequent resets of OBDII systems. OBDI works differently. However, I was curious to see what impact it would have - experimentation you know.
In terms of what hte ECU does...
Resetting after a new mod probably isn't a bad idea. The ECU does have to learn the airflow characteristics and you'll speed up the process this way (probably). However, the ECU should eventually learn it anyway, since the learning process is almost exclusively the long term and short term fuel trim. These values are changing all the time.
At WOT, the ECU operates in open loop mode whereby the primary determinants of engine settings are MAP, TPS, RPM, IAT and knock (I think I just posted something on this). Long term and short term trim will be applied here as well, but not altered since the ECU disregards the O2 sensor at WOT because the O2 can't respond fast enough or accurately enough.
I don't believe the ECU resets every few starts. It may dump trouble codes, but on an OBDII system, they will be stored (must be by law).
UL
First, let me tell you what happened when I did the reset again with the airbox lid on. First of all, it didn't stall on me. Second, the hand timed performance was much better (compared to before with the airbox lid on).
Marcucci, I don't know if it was me who recommended that to you, but I don't advocate frequent resets of OBDII systems. OBDI works differently. However, I was curious to see what impact it would have - experimentation you know.
In terms of what hte ECU does...
Resetting after a new mod probably isn't a bad idea. The ECU does have to learn the airflow characteristics and you'll speed up the process this way (probably). However, the ECU should eventually learn it anyway, since the learning process is almost exclusively the long term and short term fuel trim. These values are changing all the time.
At WOT, the ECU operates in open loop mode whereby the primary determinants of engine settings are MAP, TPS, RPM, IAT and knock (I think I just posted something on this). Long term and short term trim will be applied here as well, but not altered since the ECU disregards the O2 sensor at WOT because the O2 can't respond fast enough or accurately enough.
I don't believe the ECU resets every few starts. It may dump trouble codes, but on an OBDII system, they will be stored (must be by law).
UL
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From: Port Washington
Another interesting observation: The Mugen ECU "relearns" differently than the stock ECU after being reset...
Reset the sock ECU and the car runs pretty normally during its learning cycle... maybe not optimized but runs close to what you call normal.
Reset the Mugen ECU and for the first 5 minutes when cold and first started, the engine cycles through very rough 1000-3000-1000 "cycles"... VERY noticable... 1000, 2000, 3000, 1000 etc... after about 2 - 3 days of this the car idles perfectly when cold at ~900 rpm...
Just an observation...
Reset the sock ECU and the car runs pretty normally during its learning cycle... maybe not optimized but runs close to what you call normal.
Reset the Mugen ECU and for the first 5 minutes when cold and first started, the engine cycles through very rough 1000-3000-1000 "cycles"... VERY noticable... 1000, 2000, 3000, 1000 etc... after about 2 - 3 days of this the car idles perfectly when cold at ~900 rpm...
Just an observation...
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From: You wish
Koejing,
No direct documentation. However, friends with OBDII GS-Rs and a scan tool have noted that the indicated trim values go back to zero after a reset. I'm assuming that the S2K is the same.
UL
No direct documentation. However, friends with OBDII GS-Rs and a scan tool have noted that the indicated trim values go back to zero after a reset. I'm assuming that the S2K is the same.
UL
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Joined: Apr 2001
Posts: 2,898
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From: Fort Worth
bbsilver:
I don't believe those are the same things. They all get rid of the CEL, but that's the only similarity. Remvoe the fuse or power and you lose *all* the "stored" parameters and the ECU goes back to the way it was from the factory.
UL:
I believe you "kicked some knowledge" on me once about OBD2 learning more than just fuel trim. I agree, but will politely disagree about frequent resets. I've experienced it firsthand, frequent OBD2 resets yield power in Hondas. I'm not sure why, but it does more for WOT performance than I expected. I suspect there is a lot going on we really don't understand yet in that ECU (at least that I don't understand!).
koejing:
I have to crack ours open to look, but the last several Honda ECUs I've broken open used OKI processors with everything on-board. The actual code is masked ROM and then everything else is RAM. From what I've seen there is no flash- remove power and all your "stored" parameters are gone.
Shaner:
Did the Mugen come with any documentation? I can understand why Honda didn't do a "learn" procedure like that, but don't see why the Mugen would need to. Or is it just some cute feature that us brutish Americans don't appreciate?
I don't believe those are the same things. They all get rid of the CEL, but that's the only similarity. Remvoe the fuse or power and you lose *all* the "stored" parameters and the ECU goes back to the way it was from the factory.
UL:
I believe you "kicked some knowledge" on me once about OBD2 learning more than just fuel trim. I agree, but will politely disagree about frequent resets. I've experienced it firsthand, frequent OBD2 resets yield power in Hondas. I'm not sure why, but it does more for WOT performance than I expected. I suspect there is a lot going on we really don't understand yet in that ECU (at least that I don't understand!).
koejing:
I have to crack ours open to look, but the last several Honda ECUs I've broken open used OKI processors with everything on-board. The actual code is masked ROM and then everything else is RAM. From what I've seen there is no flash- remove power and all your "stored" parameters are gone.
Shaner:
Did the Mugen come with any documentation? I can understand why Honda didn't do a "learn" procedure like that, but don't see why the Mugen would need to. Or is it just some cute feature that us brutish Americans don't appreciate?