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View Full Version : Compression Ratio..How High???



zermatt7
01-02-2004, 12:34 AM
Whats the highest (safe) compresion ratio yuo can run on a 300ex and still use pump gas...(91-93octane)...?

I read the new yamaha is @ 10:5 to 1.

K_Fulk
01-02-2004, 12:42 AM
It varies by machine, but usually between 10:1 and 11:1.

member
01-02-2004, 01:04 AM
id just go higher and spend the extra $$ on high octane gas :) i hear there is a big diff. in power

Aceman
01-02-2004, 07:27 AM
You go any higher than an 11:1 piston and you will need a heavier connecting rod.

400exdad
01-02-2004, 12:25 PM
Stay between 10 and 10.5 to 1.... just run premium pump gas. The newer quads can run higher comp. ratios because they are liquid cooled and can get rid of the heat better.

zermatt7
01-03-2004, 10:49 AM
Thanks for the advice....

hondafox440
01-03-2004, 11:37 AM
Originally posted by 400exdad
Stay between 10 and 10.5 to 1.... just run premium pump gas. The newer quads can run higher comp. ratios because they are liquid cooled and can get rid of the heat better.

Not exactly. Higher octane fuels are more resistant to detonation, meaning exploding due to the pressure of the piston (like in a diesel engine) instead of exploding when the plug fires. The slight difference in engine temps between an air cooled engine and a liquid cooled engine really won't affect this at all.