Curious about compression ratio.

[DSMsamurai666]

How do you choose a compression ratio when you buy pistons? I fully understand what compression ratio is and that most cars are 10:1, but lets say I hypothetically was building a high performance motor that I wanted to produce like 5 or 6 hundred + horse. Would I want a higher ratio? Also, I'm sure it also depends on boost, but when does the compression ratio begin to induce knocking on pump gas?

I was checking out the brian crower stroker kits and day dreaming about building my GSX.

 

[JEFFREYCASTGSX]

Well for a street driven car you wouldnt want a high compression. For a car that sees e85 or something of the sort then you can take advantage of the higher compression but for the most part stick with a low compression for high horsepower. Boost can induce knock at almost any amount, it just depends on a number of factors.

 

[DSMsamurai666]

So if I ever get to building like a 600 horse 4g63 race car, stick with 10:1 huh?

 

[UGOT8UP]

Detonation kills engines not compression, you can make a 10:1 DD engine but it will take a cold plug due to the high compressoin having a faster burn rate and E85 will be a big plus, but idea I like a 8.5:1 piston for DD duties.

 

[toofast82]

Yeah 10:1 on pump gas will keep your boost and timing down very low. If you plan on running e85 or race gas, you can take advantage of a more aggressive tune. For a dd, i wouldn't really go any higher than 9:1 so youre still fine with pump. The higher compression will give better off boost response and spoolup too.

 

[marcmsj]

stick between 8.3 and 9:1 and you can't go wrong.