Easy way to get out of low octane fuel table?
01-19-2004, 02:41 AM
#1
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Easy way to get out of low octane fuel table? When the PCM records a few incidents of spark knock it will lock the engine into the low octane fuel table.
Is there any way to force the PCM to go to the high table other than adding 5-gallons of gasoline ('02 Corvette Z06)?
At the track in the hot summer months, with low octane fuel, I've had the car go into the low tables. Even though I add 5-gallons of high octane gas, unless it has time to circulate completely thru the fuel system and get to the injectors before I make another pass, it will get a few incidents of spark knock on the old fuel in the fuel rails and that will cause the PCM to start using the low octane tables again, wasting the high octane fuel I just put in.
Is there any way to force the PCM to go to the high table other than adding 5-gallons of gasoline ('02 Corvette Z06)?
At the track in the hot summer months, with low octane fuel, I've had the car go into the low tables. Even though I add 5-gallons of high octane gas, unless it has time to circulate completely thru the fuel system and get to the injectors before I make another pass, it will get a few incidents of spark knock on the old fuel in the fuel rails and that will cause the PCM to start using the low octane tables again, wasting the high octane fuel I just put in.
01-19-2004, 05:19 AM
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Originally Posted by FRISKY
When the PCM records a few incidents of spark knock it will lock the engine into the low octane fuel table.
Is there any way to force the PCM to go to the high table other than adding 5-gallons of gasoline ('02 Corvette Z06)?
Is there any way to force the PCM to go to the high table other than adding 5-gallons of gasoline ('02 Corvette Z06)?
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01-19-2004, 12:15 PM
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Yes, very good info! Thanks!
That explains why it was still using the low-octane fuel table even though I had added high-octane gas at the track. I didn't run any logs after I left the track, so I didn't realize the timing would progress to the maximum timing table after a certain amount of time, etc...
Where do you suppose the “add 5-gallons of gas to get it into the high table” BS started?
That explains why it was still using the low-octane fuel table even though I had added high-octane gas at the track. I didn't run any logs after I left the track, so I didn't realize the timing would progress to the maximum timing table after a certain amount of time, etc...
Where do you suppose the “add 5-gallons of gas to get it into the high table” BS started?
01-19-2004, 01:14 PM
#7
It is old 'wisdom' from past ECU systems, and many current ECU's still use this strategy. It was the standard method (add 20% of fuel) that many other vehicles used to switch between ignition tables.
If somebody hadn't actually spent the time to torture their engine with poor octane, a scantool, and a dyno, we would probably still be operating under this assumption.
If somebody hadn't actually spent the time to torture their engine with poor octane, a scantool, and a dyno, we would probably still be operating under this assumption.
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01-19-2004, 05:17 PM
#9
Originally Posted by Joe Overton
bingo!!!!!!!!
). Since you need to flash for the RPM change it will be in the High Octane table 100%. GMPX told me this.......simplicity at its best!
01-20-2004, 01:32 PM
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I used to use timing tricker, you know the resister in place of the IAT. Well sometimes I had too much advance and the timing was pulled back. But when I refueled and started the motor right at the gas station it was like WOW! The motor sounded different and when I drove away I could feel timing advance was back again. I mean there was a big change. I know for a fact timing is reset when fueling, maybe not 100% but it does change. It does in my 02 anyway. Now of course I tune it myself, much better.
01-20-2004, 03:46 PM
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Originally Posted by WS6 RULES
I used to use timing tricker, you know the resister in place of the IAT. Well sometimes I had too much advance and the timing was pulled back. But when I refueled and started the motor right at the gas station it was like WOW! The motor sounded different and when I drove away I could feel timing advance was back again. I mean there was a big change. I know for a fact timing is reset when fueling, maybe not 100% but it does change. It does in my 02 anyway. Now of course I tune it myself, much better.
