Several comments:

We may be saying the same thing with different words about fuel grades. Agreed that flame fronts and detonation are not the same. High compression engines require high octane fuel which burns slower, or lets the flame front complete its business, or whatever you want to call it. Lower octane fuel could result in quenching or detonation which can cause higher combustion temp and oxides of nitrogen or nitrogen dioxide. There really is no NOX. The x stands for an unknown just as in algebra. Cars requiring low octane do not benifit from premium, and in fact may suffer reduced performance.

Engine temps matter. All California testing station are required to have a huge fan to blow air at the engine compartment during the test to simulate road conditions. Stations are not allowed to pick their own fan. Only a state approved fan can be used. These fans cannot be used at the whim of the operator. There is an ambient temp sensor built into the testing machine that tells the operator when the fan must be on. The fan could be required to keep cars from overheating during the test, but I don't think that is the purpose. I've been told the purpose was to keep temps and nox down by simulating air flow during driving. I have seen no documention to that effect.

I was an electronics technician for 10 years before I become a Mercedes mechanic. I went through one solid year of electronics school five days a week. I was taught everything there was to know about electrons, outer rings, and co valent bonds and such. My point is that in those 10 years I ran into many situations where I said," well, so much for theory".

Peter

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