What gas octane rating is recommend in the USA?
#16
Drifting
Correct me if I am wrong, please, but is not detonation simply caused by the ignition of the fuel before TDC?
Yes, but the bigger problem with detonation is when it occurs PRIOR to, or even co-incident with the ignition spark. For example spark advance is at 14 degrees but the low octane fuel ignites, EXPLODES, at 20 degrees BTDC.
The retardation of spark would then seem to be the perfect solution for the ECU to perform.
Yes, but the bigger problem with detonation is when it occurs PRIOR to, or even co-incident with the ignition spark. For example spark advance is at 14 degrees but the low octane fuel ignites, EXPLODES, at 20 degrees BTDC.
The retardation of spark would then seem to be the perfect solution for the ECU to perform.
Detonation is generally defined as simultaneous ignition of the ENTIRE A/F mixture volume. But nothing is absolute, spark ignition of a mixture that is already close to detonation can also result in a flame front that advances too rapidly.
#17
Drifting
"...caused by (spark) ignition of the fuel before TDC?...
You're speaking only of spark knock, but the most detrimental form of detonation is the result of SELF-ignition.
But in any case if you're getting detonation co-incident with the spark then the mixture was likely already on the cusp of self-igniting.
#18
Oh, now I see..
"...caused by (spark) ignition of the fuel before TDC?...
You're speaking only of spark knock, but the most detrimental form of detonation is the result of SELF-ignition.
But in any case if you're getting detonation co-incident with the spark then the mixture was likely already on the cusp of self-igniting.
"...caused by (spark) ignition of the fuel before TDC?...
You're speaking only of spark knock, but the most detrimental form of detonation is the result of SELF-ignition.
But in any case if you're getting detonation co-incident with the spark then the mixture was likely already on the cusp of self-igniting.
#19
Drifting
More gas in the mixture..MORE cooling..
Ask any GA pilot.
Same theory as DFI, vaporization (evaporative cooling) of fuel just as it enters the combustion chamber allows compression ratios of 12:1, even 14:1 in some cases.
Ask any GA pilot.
Same theory as DFI, vaporization (evaporative cooling) of fuel just as it enters the combustion chamber allows compression ratios of 12:1, even 14:1 in some cases.
#20
Drifting
Ok, I see what you are saying, but doesn't an earlier spark alleviate both types of pre-ignition? I don't see how a richer fuel mix would cause the ignition to occur any later... and wouldn't a richer mixture then cause other problems in a high compression engine? I am not a mechanic, nor a mechanical engineer, so I realize that my understanding of current technology is a bit limited.