detonation on run 1 but not after, and o2 ?'s
12-07-2003, 08:30 PM
#1
detonation on run 1 but not after, and o2 ?'s looked at my o2's today, fisrt WOT run i heard detonation but the next few i heard nothing?!?!?! why is that is that normal sometimes on the first WOT run after start up? or what?
also i looked at the o2s in 4th on the 2nd run and they were 920 and 950, normally they are about 5-15 appart why would they be so far off like this. i just did headers figured that would be part of it. what else can make the banks read different?
also i looked at the o2s in 4th on the 2nd run and they were 920 and 950, normally they are about 5-15 appart why would they be so far off like this. i just did headers figured that would be part of it. what else can make the banks read different?
12-07-2003, 09:00 PM
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dont worry about the diff banks or the 02#s from them except unless you see them take a nosedive. The car COULD be running between the octane tables. The high and low octane tables will blend into a % of which table is being used and you are more than likely running less timing then what is in your high oct table.
Jeremy
Jeremy
12-07-2003, 11:48 PM
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I wouldn't worry about it.The knock sensors are doing there job.
At the track,sometimes my car get's knock and sometimes it doesn't.I don't lose sleep over it.Of coarse I have the low octain table set the same as the high octain so the computer doesn't set a low timing.
At the track,sometimes my car get's knock and sometimes it doesn't.I don't lose sleep over it.Of coarse I have the low octain table set the same as the high octain so the computer doesn't set a low timing.
12-08-2003, 08:12 AM
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I agree the high and low should be the same, ONLY IF THE TUNE IS CORRECT. If the tune is not on the money then it is good to have that bit of leway. Many time I have seen headers cause or takeaway detonation, much of it depends on the type of header and the design. Longer primaries are very different when it comes scavenging which pulls the residual exh out and increases the cyl press on the next combustion cycle.
Jeremy
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12-09-2003, 05:10 PM
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12-09-2003, 08:07 PM
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I have not yet seen a good explanation of the refilled gas tank theory. There are some who think that filling the tank resets the timing to the high octane table. Based on that thread I mentioned, I don't think that is true. The adaptive octane scaler recovers very fast from a single knock event - just a few seconds at load with no knock (I have logged this with EFILive several times). So the PCM will stay on the high octane table as much as possible unless there is knock present. If you have enough knock to keep the timing down constantly, then you need better gas or tuning.
The fuel trims are part of the fuel management system. The high/low octane spark tables are part of the ignition control system. I don't think the fuel trims are affected by the knock retard function. But, I suppose if you had a tank of bad gas (keeping your timing down), then your fuel trims might move a little in response to the constantly low timing. Then when you put good gas in the car, the fuel trims would learn their way back to the higher timing setting. I have no idea how big this effect might be. But, I suppose it could be measurable with a scanner.
The fuel trims are part of the fuel management system. The high/low octane spark tables are part of the ignition control system. I don't think the fuel trims are affected by the knock retard function. But, I suppose if you had a tank of bad gas (keeping your timing down), then your fuel trims might move a little in response to the constantly low timing. Then when you put good gas in the car, the fuel trims would learn their way back to the higher timing setting. I have no idea how big this effect might be. But, I suppose it could be measurable with a scanner.