Yeah stoichiometric is the right amount of fuel combined with the right amount of air (O2) so that when burnt, there is no mols of air (O2) or fuel left over. less fuel = burns hotter so egt = higher. more fuel = cooler so lower egt. So does the a/f ratio depend on safe temps for the engine internals? indicated by egt?

Wouldn't it be more efficient to run at stoichiometric. Since the cars run rich it just means we are dumping fuel out the exhaust because it ran out of air to react with. But because of the increased temp/pressure from the turbo the charge might spontaneously combust instead of creating a controlled flame front?? I understand that egt can give you an indication of whether you are running rich or lean (compared to 11.X:1) if you know what the temps are supposed to be at a safe mixture.

So i suppose regardless of efficiency you need a richer mixture to ensure low enough exhaust gas temperatures which indicate safe operating conditions inside the engine? Do safe EGTs differ between cars? surely as you increase boost (and hence temp) you would need to increase a/f ratio to compensate for the higher temperature?

And on top of that there would be a different safe temperature and pressure for different a/f ratios before the onset of detonation? or does it only depend on fuel type?

Sorry for all the questions, and cheers for your answer!! I'm just curious and my brain works itself overtime on things like this.