Which compression ratio eh??

[BIGsnorlax]

Im looking around for some decent pistons for the build at hand and i am stuck between bisis 10:5 and the 12:1 pistons

I have 87,89, and 92 octane available at the pumps here so i know i can confidently run the 12:1

BUT can i still make good power (lets say ~180whp) with a 10:5 piston? or should i go the higher route?

Block will be brought out to 87 or 88. havent decided yet, and bisi head parts will be used (cam, springs retainers etc.) your typical A6 mani and exhaust will be upgraded.

anyways supporting mods aside what is a realistic goal with the 10:5 pistons? 12:1? Budget roughly 3k. So nothing extreme, basics plus rods and larger bore

[chrischhorn]

with 10.5:1 comp you should be able to do it as long as you have a great header and exhaust, looks like you got your cams planned out and be sure to upgrade your intake side also. Bigger IM with larger TB and everything port matched (maybe even individiual throttle bodies . You could also always mill the head to up the comp a bit too. Of course the 12:1 is gonna yield better gains so later if you are plannin to goin all out and for bigger numbers later then you might as well go 12:1 right now.

[prNonVtec4u]

if ALL motor, 12:1. if all motor and spray down the road or something, 10.5:1 would be easier/safer.

won't make sense to focus on ALL motor and only go "halfs" on the build with just 10.5:1.

my 2 cents

[Joey GT-R]

Agreed. 12:1 or go home.

[motobmx105]

Agreed. 12:1 or go home.

X2!!
is this a F22? im building a N/A h22 that should hit 12:1 cr or more

[wed3k]

type-s is 11:1 and you can always deck the block to get more compression. you just arent limited by the pistons themselves.

[PirateMcFred]

The nice thing about more compression is that you get better mileage as well as more power. 10.5:1's ok but if you can get away with 11.5 or 12:1 then why not take advantage of the "free" power?

Higher compression will leave you room to grow if you're going to continue modding the engine for NA purposes. I think ~180whp is not that hard but to get a cam big enough for the top end power you're likely to sacrifice low end, driveability and emissions. Just FYI.

Go for the largest displacement you can. The 5000+ rpm midrange torque can make up for a lack of peak power.

[Johnz826]

Wat engine r u dropping these pistons in?

[BIGsnorlax]

wat Engine R U Dropping These Pistons In?

F23

[GhostAccord]

If your going to spend that kind of money on Bisi (Arias) pistons you might as well get a set of custom pistons. That way you can get them made for the compression ratio you want. Why be dictated by what's on the shelf? I got a set of custom Wiseco's for $500. Running them on H22 rods they have a 29mm compression height and .6cc dome. That gives me between 11.5-12:1 compression ratio with my setup.

The numbers that are posted for off the shelf pistons are an approximate CR. Depending on your setup that will more than likely change. Best to cc your combustion chamber and then go from there to see what pistons will work for your goals.

[BIGsnorlax]

If your going to spend that kind of money on Bisi (Arias) pistons you might as well get a set of custom pistons. That way you can get them made for the compression ratio you want. Why be dictated by what's on the shelf? I got a set of custom Wiseco's for $500. Running them on H22 rods they have a 29mm compression height and .6cc dome. That gives me between 11.5-12:1 compression ratio with my setup.

The numbers that are posted for off the shelf pistons are an approximate CR. Depending on your setup that will more than likely change. Best to cc your combustion chamber and then go from there to see what pistons will work for your goals.

Good call, I was starting to realize this. Custom was always a must as I am going larger than the "shelf" pistons bisi offers. I was more interested if 10.5 was a decent bump, but i guess if i can get premium gas by me... why go low if i can shoot higher