Just my 2cent:

Your car is NOW a high compression NA car till boost kicks in. It does not have much lag with a proper sized turbo and once that kicks in at 3200-3500rpm, you get your healthy 300whp on an average kit running 8psi.

Now you will drop you compression ratio and loose torque and HP. You will than boost 2psi to make up for the difference, but your car will suck below boost.

How great is that Ask Cody how his car felt when hi dropped the CR with a headgasket and drove it aroung without boost.

In the end it's about effective CR not static CR...higher CR+lower boost or lower CR+higher boost, both result in the same efective CR and same top end power. But do you want to have a driveable car or just be able to boost 2psi more to make the same power? That is the question here....

Why is my car pulling on a EVO that has 21PSI of boost?

High compression, low boost..that's new school baby

 

i guess its hard to measure, but will the 2mm headgasket make a significant difference to driveablilty whilst offboost?

 

I think your point is even more valid for sc guys. Lowering compression when we only see max psi at redline would suck for day to day. However, as you stated, if a well set up turbo would see max boost at around 3000-3500rpm the lowered compression wouldn't matter much since you're just at 1/3 of your rpm range. I guess it would feel kinda like the parasitic loss the sc generates before it starts generating enough boost.

 

I still fail to see WHY it's better to have a 10:1 static CR and boost it 10psi compared to a 11:1 static CR and boost it only 8psi. Anyone can explain that? And sorry for so many typos.....

 

It's based on what you mainly use the car for, daily drive(lowend power) or track racing(highend power).

 

Shoot, I put that 2mm Cometic HG from Ebay in in February, and I'm driving it NA, and I'll tell you, the difference with the compression lowered by one point is _NOT_ that noticeable! I drive it hard, easy, all over, and all weather, not a prob. I'm just fininishing putting a turbo kit together, and will boost soon. But don't hesitate to put that gasket in, even if you're only going for 8 psi. Then, since it's not really necessary to drop comp ratio at that boost level, you just won't pull any timing!

Mark K.

 

So for turbo chargers is 9 or 10psi max, how much would it be for a 2mm and 3mm. Is it turbo dependent?

 

There's a guy on this forum somewhere who's running 14 (!) psi on stock (!) headgasket. But I think he has a standalone EMS, such as an AEM EMS 1052.

You can do a bit less if you use stock HG and:

Emanage Ultimate

even less (PSI):

Emanage blue

Even less:

FPR.

In other words, the better and more advanced the engine management, the more safe psi you can run on each respective setup. (setup in terms of headgaskets or Comp. Ratios in general). All of them, of course, with a really good tune.

more in terms of boost:
--> more
FPR Emanage E-Ultimate AEM EMS or
| M K-Pro
| o Stock HG
| r 2mm HG
\/ e 3mm HG
lower CR pistons


Just a rough table, I won't plug any numbers in, as they will vary wildly all over due to differences in setups.

Mark K.




It's prolly more EMS-dependent.