Combustion - was Re: Propane EFI

[Padgett 0sirius]

Uh folks, as far as energy per gallon is concerned, gas is gas, it is
all the same. What octane measures is how fast it burns and to a lesser
extent ignition pressure. Higher octane gives slower burning & more
resistance to "spontaneous combustion". The secret to a SI engine is
controlled combustion. Since the pressure rise is not instantaneous
mechanical spark advance is needed. Since the burn rate varies with 
chamber pressure, you also need vaccuum advance. The goal is for peak
cylinder pressure by about 10 degrees ATDC (varies a bit with engine
geometry). This will vary for any fuel used.

Might I suggest review of chapter 1 "Combustion" in Ricardo's "The High
Speed Internal Combustion Engine" ? Is better than Obert.
      	A. Padgett Peterson, P.E. Cybernetic Psychophysicist
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