Compression ratio calculations for aftermarket forced induction systems

[supra411]

Hi:

I have a general technical question for the professionals (like suprasport):

How do you guys calculate the right compression rate for a car that is being introduced to a turbocharge system. Like if I had a s2000 with compression ratio or 11.0:1 (that's stock), and I want to add a Garrett T-04 in it with compression inducer of 40mm, what should the new compression ratio be? What are all the littles things that goes into calculating the compression ratio? I just want to learn more about turbos and how they effect the engines. Thx for all your help!!!

What are stuff should I also change other than:

1. Exhaust system
2. Fuel injection

... to make the car better?

Thx
Ricky Cheung

[supra411]

Am I posting in the wrong section???

Thx
Rick

[ASL MKIII]

Are you asking what you should reduce your compression to? Or are you asking if adding the Turbo will change your mechanical compression ratio...?

[aljordan]

I think he's after effective compression ratio. i used to know this a few years ago.. but i've forgotten.

http://www.smokemup.com/auto_math/eff_cr.php

The above should help. I wish i knew the formula tho.

[supra411]

Thx for everything, but I'm still a little bit confuse.

The static compression ratio is the original compression ratio while the effective compression ratio is the new ratio with boost, right?

I want know to know how low should I lower my compression ratio if I want to add a turbo w/ avg. 12lb of boost.

Thx
Rick

[aljordan]

8.5 to 1 compression ratio is about perfect for boost applications. You'll need new pistons in order to do this. You can run a thicker headgasket, but I'm not a fan of doing this. You may not get to 8.5 to one, but you will lower it.

High compression and boost are a wonderful thing really. You get the better low end response, and the high end pull of a turbo.