[Diy_efi] Timing Advance Curve?

[Eric.Fahlgren]

A6intruder wrote:

> Octane has everything to do with the speed of burn.  Higher octane actually
> controls ping by slowing down the burn.  This is why a very low HP/cubic
> inch engine doesn't necessarily gain power with higher octane.

This is absolutely wrong, the octane number and speed of burn are not
correlated in any way.  Diesel fuel burns very slowly, because it has
a high molecular weight, yet is has very low "octane" (cetane really)
number.

Burn speed does in fact correlate with detonation, but in the opposite
sense given here.  A faster burn reduces the tendency towards detonation,
by reducing the amount of them that the end gasses are exposed to high
pressures and temperatures.  Ever heard of "fast burn" heads?  They
have combustion chambers designed to promote a quicker charge burn,
thus reducing detonation.

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