Compression advice for H22 turbo

[jimmybean21]

first off im fairly new to boost just recently boosted my car last year but now i'm starting to accumulate parts for my h22 turbo build and i'm seeking advice on what would be the best compression for my build?

originally i was thinking a 9:1 compression but after picking up my block yesterday they suggested a 10:1 compression instead. so now i'm pretty much confused because after searching around i thought low compression was better for turbo.

my goal for my build is seeking to reach around maybe 500hp on pump gas and around 700hp on race gas.

any help is greatly appreciated and thanks in advance...

[mndude07]

High compression turbo is the way to go. People that do 8:1 are just scared.

[90Lx-clusive]

Isnt stock compression on the H22 10:1 already?

[mozzandherb]

For numbers that high I would recommend going with the lower compression piston. I currently have close to 400whp on a 10:1, but if you're aiming at 500-700 I think a 9:1 would be the optimal choice.

[jimmybean21]

i was thinking 9:1 originally based on the research i've been doing but i've been getting so many different numbers from others that im confused. my whole thing is i wanna build it right the first time oppose to trying 3 and 4 different setups...

[Joey GT-R]

Well before you decide on compression, what are your goals? For example, I'm shooting for around 500whp, so I'm going to go with somewhere around 9.7:1. For applications around 600whp, 9:1. If you're going 700 and beyond. You should consider like 8.2:1. Figure that out and then get back to us.

[drummersteve7]

negative. compression really doesn't have to much to do with horsepower for boosted applications. Compression will handle your Torque. Hence when you go lower compression jimmy, you will lose torque,
they recommend 10:1 so you can still have a good amount of torque from the dig without the turbo spooled up.

Consult with your tuner first, this is a specific tuner feature, if he has handled high compression builds
and has no issues tuning 10:1, go for it. Of course if you intend on spooling that turbo up with nitrous,
then go lower.

[dbsharp]

I wish I had the money to get custom pistons and have 10+ compression. but I cheeped out and got 8.5 to one. My car makes great midrange torque, but only in the higher gears. in the first few gears its slow until I get around 4k.

[Saidaigen8]

For those numbers you would want the lower compression. Stock is 10.6:1 for the guy that asked.

[MyCord]

people that say high compression turbo is the way to go. are just f ing retarded. thats assanine. low compression for any turbo build is what you have to do. h22 stock compression is 10 1 thats ok for a small turbo will little psi maybe 5-8 lbs. any thing more than that and you need block work. if your talking about making 500-700 hp. you need pistons rods the whole sha bang. my buddys got a h22 turbo. 478hp on pump gass. 650hp on race gass. his ration is 9 1 and he went with 9 1 mahle pistons, eagle rods. acl bearings, a slight bor, bigger oil pan, and thats just downstairs. head work is very important too especially with a regular h22. cams valves springs all needed to make power. crower makes awesome products that we used and have had nothing but high numbers with. none of thats includeing, the intake manifold, throttle body, and fuel system you need for that kind of power, plus you need mounts that can hold and restrain that much power. but thats other storys for other days. go low compression. and go turbonetics or greddy. and do it right

[mcdizzle]

i dont see compression being a big deal (yes i know im going to get flamed for saying that)

reason being is: it is all on your tuner. my best friend has a fully built b16 (boosted with a gt30r) thats making 521hp and soon to be around 580hp running 23-25psi. his compression ratio is 11:1 using crower rods/wiseco pistions and he is tuned on e85 (this might be what allows that but im not sure) his block was put together by ERL, his head has a full port n polish and supertech valve train with stock cams/gears. his car runs perfectly fine and outruns just about anything on the road and literally scares the piss out of me when i ride in it. it has yet to break down or show signs of unreliableness (other than the stock diff taking a shit)

so again i dont see where everyone is all up in arms over the compression ratio. when i boost my h22 which will have a similar block build to my buddys, i plan to run a 10:1 pistion setup with eagle rods.

for reference here is a video of my buddys civic on the dyno:
http://www.youtube.com/watch?v=cqHt1leUbXs

[toycar]

E85 has a lot to do with your buddies car and high compression/turbo and the reason it hasnt exploded-yet.

High compression with turbo = catastrophe.

You dont want it, you dont want it, dont do it, your going to regret it.

Turbo motors=low compression if you want it to last. If you are building a track only car, sure high compression/turbo will make good power.

However, if you plan to actually drive you car, dont do it.

High compression + turbo common problems;

-Lifting heads
-Ignition is a PITA to tune
-Race gas/E85 conversion is a must
-Short lifespan-due to excessive cylinder pressure and pre-detonation
-Crack(s)-Shit cracks under such high pressure. Air in vs air out is 10x harder to manage with high compression pistons. The turbo should be the pressure builder, not the stroke/piston in a turbo application
-Hot spots-From excessive pressure in cylinder



All in all, a good tuner will tell you NA motors are best with higher compression/stroke/rod&stroke ratio's, and turbo motors run best with lower compression/shorter strokes/shorter rod&stroke ratio.

Faster rev=faster spool
Shorter stroke=less dwell times=faster spool
Lower compression=better flow when "Flow" is dictated by a compressor not natural aspiration due to less resistance in the rotational assembly

And just to prove the point
Longer stroke=more compression-NATURALLY
Higher compression piston=more compressed air, naturally drawn into the cyliner to mix fuel with

And the reason NA motors are less likely to last is their power comes from crazy compression and high rev's, where as a turbo build will last because the "Load" never gets that high-wether it be the compressed air"Load" or the excessive rev "Load" so the stress to the components of the motor is reduced.

Think about it like this;

When you hold your finger over the end of a straw, full of fluids, the fluids dont move. When you allow the cylinder to breathe(By removing your finger)the fluids move, at a natural flow.

Fluid out=air in. A natural vacuum is created, sustaining a natural aspiration.

Replace the word fluid with piston. Piston down=air in. Thats how natural aspiration motors get air, thats why higher compression works better on natural aspiration, the air in is directly related to the piston drawing down, sucking air into the cylinder.

FOllow me?


So, in a turbo car, the air is forced into the cylinder with a compressor. Therefore, the natural flow is out of the question. Now its about the resistance of your rotational assembly, and how to FORCE the most air in and out of the motor-hence the lower compression. Lower compression=less resistance.

Thats a lamons terms explanation for you. Theres waaay more science involved as to why, but(No offense) it would be way over most readers head to understand the WHY of the answer.


High compression=NA build
Low compression=Turbo
High compression+turbo=track car that never see's 10,000 miles in between tear downs, new gaskets and freshened up.

Hope this helps

[Sordz]

If your planning to make 500whp on 91-93 octane fuel go LOW LOW compression(less chance of knock), higher compression and one bad tank of premium and your going to be in trouble with detonation. if your pump gas is e85 you could run higher since there will be less detonation with e85 as its higher octane. FYI you can also make your 700whp with e85. I run e85 and 9:1 personally and am in between your 2 #'s your looking for.

You can look at the s2000 guys making 600+whp stock motors on e85 and have HIGH compression.

Not related to thread but you can make 600whp with stock head/intake manifold/throttle body etc. and I wouldnt run "greddy" or "turbonetics" turbos.

Also not related but you better think about getting some upgraded gears for your transmission and a twin disk clutch if you dont already.