what is compression ratio

[kuwait_to]

hello all,

when i read a mong your articles i found the expresion top end power and compresion ratio i.e (9.5 : 1) what is that , and how can i calcuated or measure it.

thanx

Saad - s30 - 1978

[BuDavid]

(the cylinder volume when the piston is in the lower position/the cylinnder volume when the piston in the upper position)= in range from 9.something to 14 i assume, but normally arround 9 or 11, 9 for turbo chrged as far as i know..

[MikeW]

The compression ratio is the ratio between the volume of the cylinder + combustion chamber when the piston is at the bottom of the stroke and when the piston is at the top of the stroke. Higher compression ratios can generate more horsepower but make pre-detonation more likely. Unless your car has been modified (pistons, head, crankshaft, etc.) then your compression ratio should be whatever was standard for your model. I don't know of a way of measuring the compression ratio without removing the cylinder head.

[CoastGuardZ]

For Inquiring minds...

http://auto.howstuffworks.com/question90.htm

Paragraph five explains the relationship of fuel and compression ratio... which can be applied to term pre-detonation.

Nate