what is the correct way to choose your cr ?

[4bangr]

compression ratio ?
boost ?
octane ?
head gasket ?

 

[elementalwindx]

compression ratio ?
boost ?
octane ?
head gasket ?

Well the simple way to look at it could be:

Higher boost - lower compression
lower boost - higher compression

its the trade off.
Personally my motor will be 9.1:1 or 10:1, not sure yet. but I do plan on running 30+psi on a gt35r or better with a o-ringed .20 over 6bolt motor.

 

[TSIfreek]

8.5:1 is the best for street 93 octane. Dont get all carried away with CR on a turbo motor. Knock will get out of hand and a pain in the ass to tune a Higher compression motor on 93 . You just have more leway with lower compression.

 

[4bangr]

here are my mods, 8.5 still acceptable ?
evo 3 turbo, 20 psi
mitsu mls headgasket
ross pistons
block bored .020" over
93 octane
aem ems
560 cc denso injectors
front mount
supra fuel pump rewired

 

[v2ner]

8.5 should be perfectly fine.

boost = depends on turbo, what kind of fuel, and fuel system (pump, injectors, afpr)
octane = depends on how much you want to boost w/out knocking your motor to bits
head gasket = is a must when doing 25psi+

 

[elementalwindx]

o-ringing the motor helps at 30+. So does water/meth injection. Good ol cheap WI best bang for the buck.

 

[Big Woo]

First you need to ask yourself a few questions.

1: How important is off boost responce
2: How much boost do I plan on running
3: What type of gas am I going to use
4: What is the car's primary function going to be.

After this the questions become a little more specific.

 

[drivemusicnow]

First you need to ask yourself a few questions.

1: How important is off boost responce
2: How much boost do I plan on running
3: What type of gas am I going to use
4: What is the car's primary function going to be.

After this the questions become a little more specific.

I personally think the most important question is, What can I effectively tune for. It really depends on how much time, and what kind of money you're putting into tuning of your car.

 

[Big Woo]

Well I agree that tuning is very important, but tuning is very important wether you choose a compression ratio of 5:1, 12:1 or somewhere in between.