11 to 1 etc refers to what?

thnx

 

Imagine the piston at its lowest point in the cylinder.
Measure the volume.
Imagine the piston at its highest point in the cylinder.
Measure the volume.

The ratio between them is compression ratio.

http://en.wikipedia.org/wiki/Compression_ratio

edit : typo.
(I hope I caught it in time... )

 

Also note that the S2000 has a relatively high compression ratio for a production car. In contrast, my 1.6 liter Miata engine has a 9.5:1 compression ratio. Primarily due to the lower CR, it can run on regular gasoline (87 octane) whereas the engine in the S2000 (F20C or F22C) must use premium (91 or higher octane).

Diesel engines, like the Navistar 6.0 liter PSD found in my wife's F250 runs much higher compression (over 18:1). This is because diesel engines ignite due to increased temperatures from compression (remember the ideal gas law pV = nRT from freshman chemistry?) rather than a spark source.

 

what implictions does a higher CR have? more prone to knocking? higher pressure in the chamber? ultimately more power compared to lower CR?

nevermind, just read the link. it says the supercharged engines usually have lower CR and i wonder how the SC s2000 engine fits into that general rule.

 

I think they explain it very well on the Wikipedia site

 

[QUOTE=dyhppy,Aug 1 2006, 05:55 AM] what implictions does a higher CR have?