Formula for CR

[T 3 Junkie]

What is the formula for the Compression Ratio?
I have the heads cc'd
and my deck height...
but i cant find the CR formula

thanks

[Travis S]

http://www.turbofast.com.au/Tfcomp.html must have java also must convert stuff to inches

[Marc]

First you need to know the "swept" volume of the cylinder (figured mathematically from the bore & stroke)
http://www.shoptalkforums.com/viewtopic.php?t=59439
Then you need to know how many CCs are represented by the deckheight that you have - this can be determined the same way as the swept volume, but using the deck height in mm instead of the stroke (if your deck measurement is in thousandths of an inch, multiply by .0254 to convert to mm).
Compression ratio is simply the total of all three volumes (swept+deck+chamber) divided by the unswept (deck+chamber) volume.

If you have dishes or notches in the piston top, their volume needs to be added to the chamber volume; if the piston is domed, the volume of the dome needs to be subtracted from the chamber volume. If a head gasket is used, its thickness should be added to the deckheight when calculating the deck volume.

[Guest]

Just plug in your information here and it figures C.R. , Displacement, Etcl

http://www.aircooled.net/gnrlsite/resou ... /calcs.htm