8.3:1 or 9.0:1?

[eclipse99turbo1]

block is bored .20 over. looking at some wiseco forged pistons but dont know exactly which compression ratio to go with.

my goal is going to be about 375-450hp

i am also throwing in BC 272/272's

i am planning to boost around 18-22 psi

please let me know more about which compression to go with. thank you very much

 

[Talon2139]

well first off, with higher compression usually comes with knock, and or precombustion. I would suggest the higher one, but only if you are planning on running it with some bigger injectors, and some way to see how many counts of knock you are getting, via safc, or better yet if you have ecmlink, or dsmlink. With 18-22psi, you had better have more fuel with it, even if you have like 1g pistons, which are 7.8:1. I learned the hard way that if you increase the air you better be adding fuel as well.

 

[tim4g63fast]

Do you own those cams yet? if not I would reccomend a different set to you.
A little more expensive but worth it.

as far as 375/450hp

what fuel do you plan on using to do that? pump, 110, c16, e85, e98, methanol etc etc etc

are you going to be spraying water/meth?

18-22psi out of what 14b haha, 16g? 20g? gt35r? hx35? hx40? BW s362? PT6765?

18-22psi is radically different from turbo to turbo?

so many variables make for different choices I would just stick with 8.3:1 your goals are acheavable with that compression ratio and its a nice streetable ratio.

I am shooting for over 600hp and my car is 9:1 no telling if ill make that but I am pretty confident.

 

[forcefed86]

Run E85, you'll be good to go with higher comp.

 

[kahl23]

Personally use 8.3:1 with no complaints. Car ran 12.052@116 on the 16G and then 11.9@122 on a shakedown pass with the 3052. Unfortunately a miss shift on the next run trashed the head and then life got in the way, so she's still down. Car also felt very good on the street with both of those turbos, so the lower compression really didn't have a noticeable effect on spool.

 

[My1GLaser]

8.3 if you are running an SAFC & pump gas.

9:1 if you are running E-85 or ECMLink or both.

 

[Hubbell91Tsi]

go 9:1 or higher with e85... i wish i was running 10.5:1

 

[Spdfreak]

go with 9:1 compression a decent tune and good fuel system and high octane 110 atleast you shouldnt have a problem with detonation or knock to make that power

 

[Migsubishi]

I would go 8.8:1 like the evo stock compression all day fast on pump gas, if your not after greatness why complicate things?

I run 10.1 and love it, but I run 93/E100 and will soon try out 12.5 like the big dogs... it's all about the fuel used

 

[Boost_Addict_88]

+1 on 8.8:1 compression. This is what I plan on running in my new motor. Its great for daily driving, especially if you can't get to an E85 station. I've heard a lot of good things on it, plus its not a b!tch to tune like 9:1. Its really up to you on what compression you run, it depends on what its going to be used for, but for dd, go with 8.8:1. Just my .2¢.

 

[Full Arsenal]

9.0:1 for the street. That's what I run in my motor

 

[97eclipseNT]

I'd go with 9:1 its not really that high of a CR and you'll have a little more off boost power.

 

[Migsubishi]

First of all, what type of fuel management are you using? If you can't control timing you might want to chill on the compression.

 

[HurleyTSi]

Just run 9:1, it really isn't that high of compression. You can worry about knock no matter what pistons you're running if your fuel system isn't up to par. That's just basics.

Running higher compression means you'll have better off boost power, quicker spool, and a smoother powerband because you won't need to run tons of boost to make power at high rpm, you'll have some low end there too.

 

[Migsubishi]

Just run 9:1, it really isn't that high of compression. You can worry about knock no matter what pistons you're running if your fuel system isn't up to par. That's just basics.

Running higher compression means you'll have better off boost power, quicker spool, and a smoother powerband because you won't need to run tons of boost to make power at high rpm, you'll have some low end there too.

I disagree, He will have more off boost power this is true but not quicker spool up due to the fact that increasing the efficiency of the engine lowers the exhaust energy produced by the engine therefore spooling the turbo slightly if any slower.

However the increased torque from the added compression will leave the driver feeling no different in spool. Knock however with all things the same and no way to control timing in peak torque areas can become a problem with raised compression. The more compression you add to an engine the closer you bring that engine to detonation and the better the tune and fuel you will need.

 

[420a-t]

Do you own those cams yet? if not I would reccomend a different set to you.
A little more expensive but worth it.

Why do you say that?

As for the OP, answer what type of fuel management and then we can tell you what would be best. What would you like, more responsiveness down low, or lower compression to soften the blow of knock (if youre not an experienced tuner) and more boost to produce the same numbers?

Why are you looking at forged stuff for 400hp? There is a cheaper way if this is going to be your final goal (which it almost never is).