why is rich better for power ??

[Seth]

On Sat, 6 Sep 1997, Johnny wrote:

> Robert Harris wrote:
> > 
> > Try this thought pattern.  Gasoline is a blend of different chemicals -
> > ranging from methanol, butane to toluene etc.  Generally speaking
> > the lighter chemicals have higher latent heats of evaporation, octane,
> > and quicker burning. The heavier chemicals generally contain more
> > total energy but take longer to burn.  Sort of like kindling to logs.
> > 
> > By richening the mixture past stoich, more lights absorb more heat,
> > thus cooler denser mixture.  They are also higher octane - more
> > tolerance to detonation and they burn more uniformly faster. Kind of
> > like a fast bonfire  - more heat, more power, big chunks (heavys) left
> > unburnt. Over stoich means less efficiency - but higher power because
> > of faster wasteful combustion with more heat.  Also complete combustion
> > requires several stages which take time.  Rich mixtures generate more
> > heat from early stages and less from the slower burning later stages and
> > run out of oxygen and just throw away the slower heavys.
> > 
> > Now is every one confused????
> 
> No not at all. I got it... I just pull into the gas station and I say,
> "fill-er-up, and give me the stuff that has lots of logs in it, not that
> crap that's all kindling". ;)
> 
> BTW, the slower burning elements have the higher octane rating.
> 
> -j-
> 
I wonder about this as the reid vapor pressure, burn rate, and molecular 
weight of several constituents of gasoline that are considered "octane 
boosters" are quite different.  


Seth Allen