From what I have noticed Honda engines make more horsepower from higher compression pistons and a few other things, that's why a Type R has more horsepower than the GSR engine. I am going to buy forged pistons to put in a GSR engine that I plan on adding turbo to. I am having a hard time deciding on what compression pistons to get. I want to put higher compression pistons but I keep reading about how higher compression engines can't handle alot of boost. Wouldn’t getting lower compression pistons mean I am going backwards in horsepower? Lets say that I was going to race the same GSR engine with the same PSI of boost.
I have 8.5:1 pistons and he has 11.0:1 compression pistons. Wouldn’t he win because he’s got the higher compression pistons?

 

i would run like 9.8:1 or 10.1 and when you go turbo just run high octane and boost on it

 

Probably, but who do you think will have to rebuild first? Boost and high CR *usually* don't go to well together for daily driven street cars. Depending on how much boost you plan on running I would go with 9.0-9.5:1. Also consider that the higher the CR the less margin for error while tuning. And 93+ octane is implied when talking about boosted HoMoCo engines.

James

 

I have run both 8.5:1 compression, and 11:1 compressoin on STREET driven cars. To tell you the truth, high compression will give you a better torque curve and make power easier than lower compression. You will have better off boost drivability as well. When i ran lower compression, it didnt feel that much different, and the car was just as fast. Off boost it was a bit more sluggish, but nothing a bit more timing could cure. Think of it this way, one bad tank of gas on a high compression boosted engine and kiss it goodbye. That was my reasoning to switching to lower compression.

 

High Compression and Low boost is great for the street. 11:1 comp and 5 psi of boost will feel great on the street. For the street you want quick reaction from the car and very little lag. With the higher compression, you will eliminate turbo lag, most t3/t4's, and you will have the quick reaction from the car.

Most people would be too scared to do 11:1 comp and boost w/o a good tuner but let me tell you it's GREAT!

For most street cars, I like to use 10:1 compression because it's right there in the middle. It's not too much and it's not too little. You dont want lag on the street.

Low compression is a thing of the past.

 

it's all about tuning....shiet, I ran 9.8:1. The only limitation on higher compression is the max boost you can run on certain octane, i.e. 93 or 100 octane and etc..

stan

 

Im running 10:1 pistons with a milled head so my cr is about 10.4:1 and i love it. There is plenty of power available even before boost kicks in.