I'm going into an engine build and need to know how to figure out the optimal comp. ratio. I have some fairly large cams in the motor right now, how does that affect my CR needs? I don't want to just pick a number out of a hat and decide that is the CR I want. I also need to to be able to run the car on 93 octane pump gas.
Also, does headwork affect the CR? And if so how? Thanks a lot people.

 

Well im guessing your looking for an equation to figure that, wich i know of, but dont have...but bigger cams wont work unless you up your CR, or it would be "overcamming" ur motor...also, headwork such as MILLING will up the CR...Hope i can be help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxhybrid85 &raquo;</TD></TR><TR><TD CLASS="quote">I'm going into an engine build and need to know how to figure out the optimal comp. ratio. I have some fairly large cams in the motor right now, how does that affect my CR needs? I don't want to just pick a number out of a hat and decide that is the CR I want. I also need to to be able to run the car on 93 octane pump gas.
Also, does headwork affect the CR? And if so how? Thanks a lot people.</TD></TR></TABLE>


How large are the cams? What are the temps in your area? what does the engine has as bolt ons and mods? who is your tuner?
What kind of headwork? like stated above milling increases CR, but you need to be more specific so people can help you....not trying to be an *** or anything, is just that if you ask a question vaguely, you will get a vague answer..

 

The engine is a brown top ZC (JDM d16a1), the cams are .418 lift and 228* duration for both intake and exhaust. I have a CAI, bored throttle body, 4-1 header, high flow cat, 2 1/4" exhaust. I have no head work done as yet but plan to have some done. I just don't know what yet, I need to know if porting will affect the C/R. The temps here are pretty mild, maybe a few weeks in summer it gets into the 90's. I also have a Zex dry kit, that I would like to retain after the motor build.

 

What cams are you running?I haven't been able to find anyone with cams besides JG engine dynamics and I actually made 50 whp more with my stock cams.

 

I'm using Gude cams, but they are meant for NA. It makes sense you made more hp with the stock cams. Aftermarket cams are usually made so you have more overlap which is bad for a turbo motor. All you boost was going out the exhaust ports. Gude does have a turbo grind though, I'd check it out. I've been impressed with mine. The only problem with them is it took me four months to get my core charge back from them. You can call them though and get tech support right from Bill Gude which is pretty cool.

 

The JG cams were meant for Turbo(JG1001cams).Maybe the gudes would be better.

 

Holy crap you had turbo cams and you LOST power?! Did they take em back and give you a refund? Maybe the Gude ones would be better. I bought a throttle body from them and it had a bad TPS on it. I called em and they shipped me a good TPS that day no questions asked. I'm going to call them today, I want to find out about the turbo cams too. I'm going to slap on this 14b I've had laying around.