Highest Octane For Stock ECU??

wstar

I agree that with an older engine/ECU, given a fixed set of engine parameters from the factory, running a higher-than-necessary octane rating is total waste in every respect. However, we know that even on a traditional engine, higher octane fuels allow tuning headroom. When tuning the A:F ratios and the spark timing, you can account for higher octane fuel and get more power that way. The flipside is by tuning for say 110 octane race fuel, you've now made a car that will knock on regular pump gas.

The big question mark with our cars is: given a stock ECU, is the stock ECU smart enough to tune itself upwards for a higher octane fuel automatically? We already know that the stock ECU knows how to de-tune itself when presented with lower-octane fuel by using sensors to detect the onset of knocking and making the appropriate adjustments.

There seems to be some evidence that, when given a much higher octane fuel, our ECU will slow retune itself for higher power using those same sensors as a guide. I find it a bit hard to believe myself, but someone did do a dyno with some 110 race fuel and showed some statistically significant gains a while back.

Edited to add: Even without "oxygenated" fuel, just plain higher octane does allow a higher horsepower tune. By making the fuel more knock resistant, the timing can be advanced further without knocking, which results in more power.

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