Fw: [Diy_efi] compression ratio

[TVS]

> I was under the impression that the only you
> run richer than 14.7:1 is for the cooling effect of the fuel, right? or
> wrong?

I'm sure somebody can word this better than I can... but in simple terms a
mixture ratio of 14.7 will result in some unburned oxygen and hydrocarbon
being present in the exhaust gas. Obviously the key to making power is to
burn all the oxygen, as this is the most difficult substance to get into the
cylinder to start with. In order to do this there has to be an excess of
fuel to ensure all the oxygen molecules come into contact with fuel during
the power stroke. i.e. maximum power is made at ratios richer than 14.7 and
somewhere around 12:1. Its the opposite for economy where you don't want to
waste fuel and so an excess of oxygen is necessary to ensure almost complete
combustion of the fuel present. e.g. 16:1. Hope this is reasonably accurate
and of some use! Toby



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