Compression

[MidNightRacing]

Lets say i wanted to run a 20g turbo at full boost what compression shoud the pistons be?

[TWISTED II]

8:1 or 9:1 somewhere in between there.

[Hodgson316]

20g!?!?

[seth98esT]

20g is a pretty small turbo nowadays compared to a lot of the big hybrid turbos there are. Compression can be 12:1 if your car was built and tuned to handle it. But lower compression is safer and easier to tune. Wisco and a few other brands make some 8:5.1 pistons.

<div class='quotetop'>QUOTE(seth98esT)</div><div class='quotemain'>20g is a pretty small turbo nowadays compared to a lot of the big hybrid turbos there are. Â*Compression can be 12:1 if your car was built and tuned to handle it. Â*But lower compression is safer and easier to tune. Â*Wisco and a few other brands make some 8:5.1 pistons.</div>
Yessir. "Full boost" on a 20g isn't a good idea though. Turbos all have an efficiency range (typically somewhere in the 78% area) that you need to stay within for the most power. I forget where this is on a 20g, but it's not at the maximum boost pressure supported, that's for sure.

[peanotation]

8.5:1 pistons would be good, wiseco makes them. get some Eagle rods as well

[naughtika]

do they make rods and piston for 6a12?

<div class='quotetop'>QUOTE(peanotation)</div><div class='quotemain'>8.5:1 pistons would be good, wiseco makes them. get some Eagle rods as well</div>
I'd go higher than that. 8.5 won't spool that 20g as nicely as a slightly higher compression would.

[MidNightRacing]

Wait im confused here with the boost the turbo gives doesn't that raise compression? so i would have to go with a lower compression also arent the stock spec. 8:1? or am i thinking with n/a car you need a low compression piston

also lets say i get 1mm+ valves would that affect what bore i need on the block?

<div class='quotetop'>QUOTE(MidNightRacing)</div><div class='quotemain'>Wait im confused here with the boost the turbo gives doesn't that raise compression? so i would have to go with a lower compression also arent the stock spec. 8:1? or am i thinking with n/a car you need a low compression piston

also lets say i get 1mm+ valves would that affect what bore i need on the block?</div>
Well, I can't really understand what you're trying to say in the first part, but i'll do my best to answer.
A turbo doesn't raise static compression, it raises effective compression. Two very different things. 8.5 or 9:1 on 24lbs (which I believe is right inside the 76% efficiency island on a 20g for a 2.0L motor) will be a fine compression. That's somewhere around an 18:1 effective compression, which is fine for C16 race gas.

No, getting oversized valves will not require you to get a different bore on the block. However, I wouldn't reccomend spending the money on them right now unless you're going for a full build. They're expensive and you have to work the head pretty well to pull power out of them.

[MidNightRacing]

<div class='quotetop'>QUOTE(scootinintegra)</div><div class='quotemain'>
That's somewhere around an 18:1 effective compression, which is fine for C16 race gas. Â*

However, I wouldn't reccomend spending the money on them right now unless you're going for a full build. </div>

Thats pretty much what im trying to say i need to say in a compression range to use 93 octane not any racing fuel with out predetonation
if a 9:1 compression will work fine then thanks for clearing it up. Its jus some times you hear incorrect info untill you look it up.

and yea its a full engine build I got a bear block and head that i wanna work to my goal of 375- 400 chp

[TWISTED II]

go with wisecos pistons. thats what i had in my galant, and was planning on making a lil over 400 hp. they are either 8:1 or 8.5:1.