For tha basic build for this project: http://www.j-body.org/forums/read.php?f=30&i=31299&t=31299 once its all good and running, it will be boosted eventually hoping to yield about 250-300hp. And from what I understand, rods start to go around 280. And for the first "stage" of this build, we will run low boost as to not get above the 280hp mark, but rebuild the top end during the off-season months of the car, including: Mild home-done port work (I have some experience in this), I am thinking keeping the factory cam would be a good idea for boost, or a custom one with just higher lift if anything. For some reason I dont think a stage 1 cam would be good. The intake mani will be port matched along with the custom turbo manifold. An overbored throttle body will be used as well. Head decked

If I have time and money ill do both "stages" at once, but the second stage would include:
Balanced crack, forged rods/pistons, honed cylinders to remove out-of-round. And then the boost can be increased. A new head gasket will be used aswell. Aslong as the main components are strong enough, slightly higher compression may be used aswell, to keep the use of a smaller turbo and higher spool speeds but still increasing the power.

I dont plan on o-ringing it, resleeving it, or getting an aftermarket crank, because with all the work involved its gonan be costly as it is. And 250-300hp on an 800lb car will be absolutely incredible as it is, no need to spend more money to have less traction.

What would you guys suggest for any other supporting mods JUST to the motor for boost? If we get crafty we could implement a GSR oil spraying system under the pistons to keep em cool and lubed, which is an excellent idea. I wouldnt push more than 12 pounds through the motor anyways. So I should be sitting between 250-300 assuming all goes well.

I havent researched the compression ratio of the ecotec stock, bu I assume its probably around 9.5-10, so if I were to increase the ratio with forged rods and pistons is it true the crank can hold up to 500hp? I read it somewhere, I really dont wanna be swapping cranks, but I dont wanna be breaking anything either.

The custom manifold will cost some time and money as it is, but atleast the SS flange from manta is only like 125 bucks, which is tolerable.

This is still planning stages, so please excuse any ignorance.

Trying to keep the required mods to a minimum, just enough so it can breathe and pound.

I'd stick with the same compression or lower instead of higher compression pistons so there is less risk of detonation. If you want to keep spool times fast, just get one of those ball bearing turbos by Garret.



15.574 @ 89 mph stock

Looks like you are going after the Ariel Atom market. GOod luck.

As for the build for the ECOtec turbo. Don't raise the comporession it's at 10:1 already. You could run about 8-10psi on stock compression wiht good tune and intercooling, BUT the stock pistons will die at 300, rods at 280 like you said.

Crank is good to 550hp, get new forged rods and lower comp pistons, and you will be fine to 500hp internally.


1988 Pontiac Fiero, engine transplant underway.
2004 ECOtec, built and boosted

Why go for lower compression pistons? If its not going to be a mad amount of power, and the internals are forged, what would be the point in reducing compression? That just means you need more boost to make up for it.

Higher compression with less boost seems more practical than lower compression with high boost for a couple reasons:
1)Like I said, its not a mad amount of power, so its not going to over stressing anything
2)Use of a smaller turbo that you can top at a lower number (say 8psi) and have the same benefits of a lower compression with say 11psi boost. Except when you arent in boost on the lower compression you will have less power.
3)The torque output would increase more than if it were lower with higher boost
4)You have full boost at less revs

Unless Im missing something, im not new to turbos, but Ive never installed one, so if I am missing something, please fill it in for me

You're running a turbo. Forget about torque, since there will be more than you can ever get tired of.

If torque is your only reason for getting high compression pistons, you will be sorry you did because of the problems it will cause you (ie detonation and need of higher octane)



15.574 @ 89 mph stock

You would need higher octane for higher boost too, less boost + more compression would be the same, needing 92+ octane.

I dont mean to argue, im honestly trying to figure this out but,
what makes high compression with less boost worse than low compression high boost for detonation? Go technical if you have to

I believe it's a lot easier to tune when you have low compression



15.574 @ 89 mph stock

Low as in what? 8? 9? or even a small change to 9.5? I suppose that makes sense to be easier to tune.

I wonder what the power curves would look like with either scenerio, anyone got some theoretical information to add? I think torque would be higher with higher compression

ddidn't you say that you were getting your block 0 decked? that'll raise you comp just a little, prob bout .2-5 / never built on these blocks so not sure. on my 406sb raised bout .4 with a zero deck

If you want a quicker spool time don't get the big pssssst sound bov, get one that recirculates the Blow off air back into the intake side of the turbo. Kinda like the 1gen dsm bov (in stock form of a stock car)

fd fk wrote:Low as in what? 8? 9? or even a small change to 9.5? I suppose that makes sense to be easier to tune.

I wonder what the power curves would look like with either scenerio, anyone got some theoretical information to add? I think torque would be higher with higher compression

I think the difference would be so minimal (if any) that you will regret it. And when I said you needed to run higher octane, I meant that if you need to run octane 91 with low compression, you will probably need to run 94 or higher with high compression.

There is a reason why nobody goes for high compression when they are boosted. If you wish to go to the other way, it's at your own risk.



15.574 @ 89 mph stock

My pistons are 8.9:1. I will run around 15psi. Water intercooled as well. Why? Its gonna be a street car, it will run on 92 octane and I don't wnat any detonation.

Lets say you get forged internals with stock 10:1 comp. ratio. You won't be able to run much boost, at most 8psi until you start doing a good intercooler setup and a very good tune. You will be trying to fight detonation more than the other setup. AF ratios richer than Rich Best Torque are gonna have to be used to cool the combustion chambers down and you will use more fuel and not make the best power you could.

Both can be done just fine, but if you are gonna put forged internals in it, might as well lower the ratio while your at it and have room to add more power down the road.....cause everyone wants that.

As for torque......the lower compression ratio turbo system if designed properly will have a larger under the area torque curve which is what people should look at.

There is no better one, they will both work but your appliocation will direct your engine.
Street? Strip? Full Race?


1988 Pontiac Fiero, engine transplant underway.
2004 ECOtec, built and boosted

see i can see the benifit of low compression and high boost. But if you look at alot of honda guys they will raise their compression and lower the boost. Personally im gonna bump up the compression a little bit and run lower boost. Detonation shouldnt be a problem if properly tuned on 93 octane. I also will have water injection but 15 psi on 11:1 on forged internals will be a nice hp gain. But we shall see what the future holds.


*2012 mazdaspeed3*