What is the highest compression i can run with 93 octane? I have heard the i shouldnt go any higher than 12.5 to 1. Is this still too high or can i safely run 93 octane with this compression ratio?

 

I would say 12:1 should be comfy. My setup is approx.12.1:1 and seems to be working good on 98RON, which is similar to your 94. I have no issues with it at all. Besides, good power can be made without super high CR.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Pondus &raquo;</TD></TR><TR><TD CLASS="quote">Besides, good power can be made without super high CR.</TD></TR></TABLE>

Also keep in mind that if increasing compression requires retarding the timing, you will end up with less power than you would have with lower compression and more advanced timing.

 

not necessarily. sometimes you'll gain power- if the pistons don't have to try to compress the expanding gases pushing back downward (when spark is more advanced on compression stroke), you can reduce pumping losses. if you have to retard timing so much that the burn is far less complete with the higher comp than using less compression and more advanecd timing, then, yes, you'll lose power, since you can't use as much of the gas. you need to find the best compromise. what combo works best? one centered around configuring the chamber to achieve the best burn, then the valves and ports to flow in as much a/f as can be burned and exhaust most completely the spent gas, so as not to ruin the fresh a/f. i've seen as high as 14:1 on a Honda B VTEC here in MI run on 93-94, but of course elevation, air temp, humidity, etc. all play a role. 12:1 seems safe, if properly tuned.

 

thank a lot guys this seems to help a lot.

 

[QUOTE=StorminMatt]

Also keep in mind that if increasing compression requires retarding the timing, you will end up with less power than you would have with lower compression and more advanced timing.