I don't agree, cite your references please

Posted by jdemaris on March 27, 2006 at 11:06:27 from (69.67.230.18):

In Reply to: Re: It is complicated - combustion chambers count posted by Tramway Guy on March 27, 2006 at 08:41:36:

I don't agree, where does your information come from? Technically speaking, it is as I stated. Various racing organizations use different rules for calculating engine size, and in each case - cubic inch displacement is whatever THEY say it is. In racing, general designations of engine size don't count - like 283, 327,350, 396, etc. When companies are selling cars, trucks, or tractors - general is fine. NHRA rules, e.g., use the variables I stated to determine cubic inch displacement, included chamber sizes. Some other racing organizations also count wear, including excessive piston to cylinder clearance above the top ring. NRA in super-stock does it different. They state
"Formula for determining cubic inch displacement: Bore x Bore x. 7854 x Stroke equals cubic inch displacement of each cylinder. The cubic inch displacement of each cylinder added together will determine the total the total cubic inch displacement of the engine."
That goes with the more common approach as you mentioned.
To be precise, which is sometimes required, cubic inch displacement is a measurement of the internal-combustion and power making area of an engine. If you could pour water into a spark-plug hole, with the piston at bottom-dead-center, and fill the area until it overflowed, and then remove the water and measure - that would be the area, i.e. the cubic inch or centimeter volumetric displacement. The thicker the head gasket, the more area. The larger the combustion chamber in the head, the more area.
And yes, of course these variables are used to figure compression. The compression ratio is a direct result of the cubic inch displacement at BTC compared to TDC. The "effective" compression ratio is a result of those factors plus the caculated amount of air that enters. This changes when atmospheric pressure is exceeded (supercharger or turbocharger), or air temperature is lowered, thus condensing the air (intercooler).

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