Orval Fairbairn wrote:

Even turbo normalizing increases the temperature of the fuel/air mix
entering the cylinders, due to compression of the air to achieve
"normal" pressures. The increased temperature increases the octane
requirements, all by itself.

Correct. That's why I only mentioned inlet temps. I've lived in the
desert most of my life and I get a demonstration of this effect every summer.
I have two vehicles that are designed to run on regular grade fuel. In the
middle of summer, when the weather man says it's 115F, temperatures above a
hot layer of asphalt hover in the 130F - 140F range. Both my truck and
motorcycle will experience detonation under load if I use 87 octane in the
summer. The motorcycle being worse, as it is air-cooled and has less control
over cylinder temps. I have to run at least 89 octane to avoid detonation.
In the winter time, I can run 87 octane without a hint of detonation.

John Galban=====N4BQ (PA28-180)

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