Originally Posted by Jafro
Nobody's mentioned compression ratios yet. Lower the compression, and your engine can handle more boost, but it will make less hp until your turbo spools.
If you're running 9:1 compression, at 19 PSI... high-octane pump gas will start to knock unless you have a REALLY efficient intercooler. Detonation will destroy a heavily boosted D-series almost instantaneously. A factory D-series rod will fold over like a wet noodle at a little more than half that much, so just treat that as an interesting fact. Running lean can cause detonation at any boost level, so your fuel trims need to be rock-solid 14.7:1 throught the whole power band at WOT if you're going to push it over 6-8 PSI on stock internals.
And it will make less hp per psi of boost. It's a stock motor so it can only handle so much power. If you want to drop the compression from 9.6:1 to 9:1 and run 2psi more, then so be it.....the final result is still the same, your limited by the amount of power being produced. Just because he can run more boost with a lower compression doesn't mean he's going to be making anymore power.....
Adding a thicker headgasket is like jogging around the block to get to your neighbors house....You can do the direct route and hop the fence, or you can spend more time and effort running around the block, then jumping the fence on the other side of his house... either way your still at his house....
Now if we're talking about a fully built car then that could be a different story....
Point being, his motor can only handle so much power before it snaps....stock compression high compression or low compression it don't matter....he still can only make so much power.
The only time I would consider dropping the compression on a street car is if your going for high hp on pump gas. And by high hp I mean high hp for the street such as 400+whp.....You can only make so much power with high compression and pump gas.......thus the need for a lower compression so you can still run pump gas....