ECU and pinging
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Joined: Apr 2003
Posts: 22
From: s.f. peninsula, ca
Car Info: 05 Legacy GT
ECU and pinging
How does the ECU compensate for pinging? Does it 'learn' about gas quality and pinging over a long period, or does it take only the most recent data? In other words, how long will it take an STI ECU to recognize that you have supplied high octane gas after using 91 octane?
One reason I ask is that my `97 2.5 liter subaru became very sensitive to gasoline (hestation due to excessive retarding of the timing) until Subaru changed the ECU.
One reason I ask is that my `97 2.5 liter subaru became very sensitive to gasoline (hestation due to excessive retarding of the timing) until Subaru changed the ECU.
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If it's pinging on low quality gas that suggests that it is already advancing the timing. ie - just as it would on high octane, which is why it is pinging.
In theory going to high quality gas should immediately stop the pinging, since the ECU should now be able to continue to advance your timing without detonation.
In theory.
In theory going to high quality gas should immediately stop the pinging, since the ECU should now be able to continue to advance your timing without detonation.
In theory.
Thread Starter
Registered User
Joined: Apr 2003
Posts: 22
From: s.f. peninsula, ca
Car Info: 05 Legacy GT
I'm actually wondering about the opposite problem: using 91 for long enough for the ECU to retard the timing. Then, using 93 octane gas and finding that it makes no power difference because the ECU doesn't reajust, say for a few hundred miles.
Its a question of how long the ECU takes to react to changes.
Its a question of how long the ECU takes to react to changes.
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Joined: Dec 2002
Posts: 8
The question now would be this:
What was the ECU programmed to do in both extremes? I don't think there is a map written for 100 octane gasoline, and so if you were to run on 100 octane gasoline it SHOULD only run at it's most optimal map, which I don't really know what it is, but most likely between gasoline grades of 92 to 93 octane and if all other conditions have been satisfied, such as temperature, altitude, pressure...................
If you want the ECU to make the corrections quickly, you should reset the ECU and drive it for maybe an hour or so. If you log, you should see the ignition timing being gradually pushed forward, but from the few times I have tried this to see if the ECU will compensate for running 100 octane gas, I didn't really see any difference from before the reset. Even with 100 octane gas the ECU would never run the kind of timing I run with the UTEC set for 91 octane......... There is definitely a ceiling to how much advance it will make, and it's mostly within street gas tolerance levels. But boy can the ECU take away your timing
What was the ECU programmed to do in both extremes? I don't think there is a map written for 100 octane gasoline, and so if you were to run on 100 octane gasoline it SHOULD only run at it's most optimal map, which I don't really know what it is, but most likely between gasoline grades of 92 to 93 octane and if all other conditions have been satisfied, such as temperature, altitude, pressure...................
If you want the ECU to make the corrections quickly, you should reset the ECU and drive it for maybe an hour or so. If you log, you should see the ignition timing being gradually pushed forward, but from the few times I have tried this to see if the ECU will compensate for running 100 octane gas, I didn't really see any difference from before the reset. Even with 100 octane gas the ECU would never run the kind of timing I run with the UTEC set for 91 octane......... There is definitely a ceiling to how much advance it will make, and it's mostly within street gas tolerance levels. But boy can the ECU take away your timing
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Maybe it's just me, but I didn't think the ECU or knock sensor operated off of an "average" principle at all. My understanding was that the ECU is set to operate at a full target level of timing based on the recommended fuel type (i.e. premium), and if the knock sensor detects pinging then it immediately retards timing (say, to compensate for 87 octane). If you empty out the fuel tank of the 87 octane, and then refill it with 93 octane, the ECU should return to full timing pretty much immediately, not waiting for several weeks to "average" it out.
That's how I understood it. Anybody know any different?
That's how I understood it. Anybody know any different?
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