Freestyle compression ratio

[rodry]

Hi guy's, i need a help with compression ratio, i know that freestyle engines are in 14:1 ratio.
I go to use a epic cdi for a good curve and retard, but still with my non pv cylinder.

To have 14:1 in my 771 cylinder i make this calculation:

0.785x85x85x68 = 385,6cc + 30cc (dome) + 3cc (squish) ÷ 30cc = 13.9:1

but my static compression ratio is:

0.785 x85 x85 x39,5 =224cc + 30cc + 3cc ÷ 30cc = 8.5:1

In pv cylinders this ratio is variable.

anyone use this compression in a non pv? are any rule between absolute and static compression ratio ?

Thanks in advance.

 

[superfreak]

Just use a compression gauge. 190-200 psi is a good compression and safe for freestyle, and runs on normal gas. I have 35cc domes and have a compression around 190, this is a non powervalve 780cc with freestyle porting.

 

[ChrisFiore15]

Compression numbers(180, 190 etc) are very different then compression RATIOS.
That being the reason the BLUE has motors that run great on pump gas, but push 220LBS PSI.. Its because of the RATIO..

 

[rodry]

I found this article that is very interesting:

http://www.bridgestonemotorcycle.com/documents/higher_compression6.pdf

"To remedy lowload
knock, the use of premium gasoline and
improving cooling are effective measures. If
premium gasoline is not used, the permissible
limit of the compression ratio is
approximately 8.4 without liquid-cooling and
8.7 with liquid-cooling"

.