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Octane rating of a spark ignition engine fuel is the detonation
resistance (anti-knock rating) compared to a mixture of iso-octane
(2,2,4-trimethylpentane, an isomer of octane) and n-heptane. By
definition, iso-octane is assigned an octane rating of 100, and heptane
is assigned an octane rating of zero. An 87-octane gasoline, for
example, possesses the same anti-knock rating of a mixture of 87% (by
volume) iso-octane, and 13% (by volume) n-heptane. This does not
mean, however, that the gasoline actually contains these hydrocarbons
in these actual proportions. It simply means that it has the same
detonation resistance properties as the described 'standard' defined
mixture.
Octane rating does not relate to the energy content of the fuel (see
heating value). It is only a measure of the fuel's tendency to burn in a
controlled manner, rather than exploding in an uncontrolled manner.
How can you have any pudding when you don't eat your meat? Pink Floyd-
1979 |
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