i was wondering if it would be a good idea to boost a k20a2 and keep the standard compression ratio. the block would be sleeved and built with carrillo h beam rods and cp pistons. would it be safer? would i just have to run higher octane gas? if the stock bottom end can make 400whp safely then shouldnt you be able to make more if the block is fully built with the same compression? thanks

 

You don't even need to run sleeves on a k20a2. There are plenty of stock k20a2 motors with just valve springs make 600+ whp. I would do pistons and rods just to be safe, but it will be fine as long as it is maintained properly, tuned correctly and not beat on.

 

i know i dont have to run sleeves im just building it as safe as possible. money is not an object. im just asking whats the consequences of not lowering your compression ratio. i dont want to lag in low rpm's bc of the lower compression alteration. i believe i can make enough power without lowering the cr and it will be strong enough with the k series not to blow, and im just wondering what could possibly go wrong. will i have to use higher octane gas or what? thanks

 

youre going to have to run premium gas regardless of what you do, premium should be run on the stock motor anyways.

I dont know what the stock compression ratio of the K20 is but my guess is that its fine.

I have a few friends with boosted stock K20s with no issues, however theyre running E85 which helps.

If youre rebuilding your motor depending on the power you want, it wouldnt hurt to lower it a tish 10:1 or 9.5:1 wouldnt be a bad choice.

 

The stock compression is moderatly fine its been done several times before

have you looked in to e85 ?

its all in the tune... talk to the individual who is going to tune the car and go from there..

 

10:1 compression is the norm nowadays. 400whp is no problem on stock sleeves. Not worth the money in my opinion at that power level. But, I'm sure once you make that power, you will want to turn the boost up, where sleeves might come in to play. If you haven't already get on k20a.org and check out the Forced Induction forum there. You can see plenty of stock motors making 600+ no problem.

 

thanks guys. ill be shooting for 6 to 700 whp. i just dont see the need to lower the cr on k series when they make close to that kind of power on completely stock internals

 

The point in lower compression is to decrease combustion chamber temperatures. Sleeved crack due to excessive heat.

 

so what would be an ideal cr for that hp goal?

 

10:1 is safe and will provide good spool-up.

 

ok thanks