Originally Posted by LantanaTX
Here is an interesting article I found about compression vs. boost. Some of what is says makes sense but goes against traditional thinking when it suggests that 9.5 or even 10:1 is better. Thoughts?
As far as I know, there's really only one reason to lower the compression ratio - controlling detonation.
You could theoretically run 15:1 + compression if you liked, but the possibility of detonation increases considerably.
If you experience detonation, then your rods will snap, or your piston ringlands will break.
This is why you can run 7psi on a 10:1 compression motor. However, if you want to run 15psi on a 10:1 compression motor, you will have to retard timing by a lot in order to prevent detonation. This results in considerable amounts of lost power - especially on pump gas. The alternative is to run rich AFR's (11:1 or even lower), but that is no guarantee that detonation will not occur, although it will help. Your EGT's will skyrocket however, and your emissions will suffer badly (for a track car this isn't so bad....)
You could easily run 15psi with reasonable timing retard on your stock engine if you were running 115+ octane, however...
Of course, there is always methanol injection or water injection, then using an EBC to disable boost if you're running low on water. Lots of tricks you can play - but the physics can't be changed.
Then the question is, just how much stress can your stock rods and wristpins take?
