HIGH OCTANE FUELS - Toyota Yaris Forums

Yaris Hilton · 08-05-2009, 04:21 PM

Higher octane doesn't mean it's harder to burn, just that it's slower to autoignite when heated to a temperature where that can occur.

Preignition is different from detonation in that detonation occurs after the spark has fired, in the part of the fuel/air mixture that hasn't yet been reached by the expanding flame front from the spark. Preignition is caused by hot spots in the chamber igniting the fuel before the spark fires. High octane won't fix that.

Marthos · 08-05-2009, 07:20 PM

Quote:

Originally Posted by Yaris Hilton

Higher octane doesn't mean it's harder to burn, just that it's slower to autoignite when heated to a temperature where that can occur.

Preignition is different from detonation in that detonation occurs after the spark has fired, in the part of the fuel/air mixture that hasn't yet been reached by the expanding flame front from the spark. Preignition is caused by hot spots in the chamber igniting the fuel before the spark fires. High octane won't fix that.

Its just the way it was explained to me years ago in Auto Tech.
laymens terms was what i was going for.

This is from a wiki

"The octane rating is a measure of the resistance of gasoline and other fuels to detonation (engine knocking) in spark-ignition internal combustion engines."

Changed that to preignition.

Yaris Hilton · 08-06-2009, 08:45 AM

Usually when you hear pinging, you're hearing detonation. If it's preignition, something's wrong with the engine that needs fixing fast.

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08-05-2009, 04:21 PM	#1
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Higher octane doesn't mean it's harder to burn, just that it's slower to autoignite when heated to a temperature where that can occur. Preignition is different from detonation in that detonation occurs after the spark has fired, in the part of the fuel/air mixture that hasn't yet been reached by the expanding flame front from the spark. Preignition is caused by hot spots in the chamber igniting the fuel before the spark fires. High octane won't fix that.

08-06-2009, 08:45 AM	#3
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Usually when you hear pinging, you're hearing detonation. If it's preignition, something's wrong with the engine that needs fixing fast.