2-Logicl

I am doing an all motor build and used cspeedracings compression guide and found that with my USDM (DAMNIT!) ITR pistons I get a wopping 10.6 c/r with a 3 layer OEM gasket. I also calculated it with a single layer gasket and got 11.1 I am wondering should I go with the 11.1 or the 10.6? I have also thought about breaking out my USDM Si pistons and dropping them in.... Where should I go with this? How much difference in HP does compression make should I even be worried about this? Plus with my valvetrain I should be able to rev up to 10,000rpm should I run an 11 c/r when going that high?

DORKO

do you plannign on dgoing boost or what...lower compression is always better for boost...and higher compression is always better for n/a setups

and if you plan on revving to 10k rpms, i would thinkhaving higher compression/strongs internals that it would do that with no problem...

but keep in mind that most stock motors stop makign power after 7-7.5K rpms

Yell88CRXsi

Compression does make a difference in HP! Hell, I'd go with the P30 pistons before using USDM ITR pistons.
If you are trying to make an "built" motor, why play with OEM pistons? Go forged pistons with forged rods!

As far as your valve train...I would not worry about being able to rev to 10k. 95% of the streetable cams will not make power that high. If even if you did...how long do you think that you would stay there? If you plan on using any OEM cams then the stock ITR/CTR valve train will do ya.
High compression = stage 2+ cams and upgraded valve train.

Remember...just because you can hit the rev limiter doesn't mean that your making power!

2-Logicl

Crower stage 2 cams and full valve train. I am just trying to get this project done now I am not trying to be the fastest thing on the planet just trying to put down respectable numbers.... Problem with the si pistons is that they are in my block and I haen't pulled the block to get the pistons out yet.... Plus it has been sitting for a while and the pistons look pretty nasty.

2-Logicl

anyone have any advice on this?

Yell88CRXsi

At 11:1cr you'll be on the low side of what the stage 2 cams will want. I do understand about budget motors and all. But if you are going to break into the bottom end...why mess with just one thing and ONLY gain minimal hp.


You want advice? Forget about the USDM ITR and Si pistons. You'll need 11.5:1 or better compression to use the stage 2 cams that you are wanting to run. If you can not get a set of CTR pistons...then spend the extra cash to do it right and buy a set of forged pistons at your desired compression.

I'm sorry, but there is no secret OEM short cut that will make power. Meaning that there is nothing that you can slap on and instantly make big numbers. Horsepower is about a blending of a group of parts...a matching.
Think of it like this. For every action...there is a reaction. Anything that you change, you need to think about how the change will affect the part before and after the part that you changed.

That's MO

steronz

yell88 is right, you're gonna want some higher compression pistons. i've got stage2 cams on a stock bottom end (10.5ish:1), and although they make about 30 hp over stock, i've got no low end because the compression's not there. i'm gonna be shooting for a 12:1 compression ratio when i do my bottom end. in the meanwhile, n2o makes up for the low (heh, i'm calling 10.5:1 low) compression.

oh, and the stage2 cams do make power well past the stock rev limiter. after my head rebuild, the hp curve was still going up when i hit the 8200 rev limit, so i socketed my ecu and edited up the rev limit up to 9600... at that point, i was still making 150whp, which was about the same as i was making at 7500.

DORKO

exactly..you when up to 9600rpm's, and you made the exact same power that you were making at 8200 rpm's..so then whats the point of revving to 9600 when you arent making any more horsepower...??
all you are doing is wasting gas,makign more noise, and possibly damaging parts of you motor..

so

unless you are like fully fully fully built race car/street car, there is no point of revving that high...even if you are makign 1 more horsepower..

steronz

nononono... 150 whp at 7500 and 150whp at 9500 with 175whp at 8750...i had to bump up my rev limiter to stay in my power band when i shift. before i fixed that, i had to shift at 8000, and i would drop down to 6000 rpms or so where i'm only making 100 hp.

2-Logicl

So some CTR pistons would work with like persay a single layer head gasket?