Thread: Twin Plug?
View Single Post
911nut 911nut is offline
Metal Guru
911nut's Avatar
Join Date: May 2001
Location: Michigan
Posts: 2,511
Originally Posted by drmatera View Post
I expect I'll need about 20psi to reach my goal of 650hp give or take a few psi
Here's the formula for calculating effective compression ratio:

effective comp. ratio = [boost/14.7+1] x static comp. ratio

Twenty psi with a static compression ratio of 9.7:1 yields an effective compression ratio of 22.90:1.

I think temperature rise in the cylinder at peak compression will yield uncontrollable temperature with resulting detonation. Also, will the structure of the engine survive these forces?

There are others who have obtained 650 hp using a 7:1 compression ratio and 1.4 bar of boost on a 3.3L engine, which is a more cost effective alternative.
Paul B.
'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb

Last edited by 911nut; 11-27-2011 at 02:17 PM..
Old 11-27-2011, 06:00 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)