Larry,
MIT has a two-volume text on the topics that we <almost>
discuss -- including the engine requirements. It isn't as easy
as CR to octane because of MANY other parameters like
heat range of plug, head design (bath tub vs hemisphere vs
wedge, etc.), valve numbers and sizes; And the list goes on.
The MIT books are a little chewy in the math department
but that is what this is all about.
The alternative is to just start compiling info from a number
of cars and look at the trends empirically. I would avoid newer
cars because many use knock-sensors that allow lower octane
fuel to be used. When a situation occurs that causes knock
or ping, the timing is dynamically adjusted to reduce it.
FWIW, my European specification '79 Ferrari 308GTB
uses 2-valve <per cylinder> heads with hemispherical
combustion chambers and mildly domed pistons. It's CR is
8.8:1. The US specification version of the same car uses
slightly less domed pistons for a CR of 8.2:1. The cost of
the lower CR is a 6% reduction in horsepower. Both may
require high octane fuel. I use 93 octane (R+M)/2 in that
car. It is not prone to ping, knock or pre-ignition. In
fact, I have never heard it do so. I include these data only
as a point of reference.
rick
> Bill great message.
>
> Now, is there some type of "chart" that would suggest which octane is
> recommended for various compression ratios?
>
> (P.S. I'll be trying the increased octane for the midriff and hair,
> thanks for the tip)
>
> Larry Hoy
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