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Originally Posted by nitrorocket
Lower the compression to 8:1 and you will be fine for 600+ RWHP with a Intercooled D1SC on 91 octane. The crank is by far the week link, it will be on the edge for sure.
Good luck!  |
8:1 is too low and outside the efficiency range for a centrifugal IMO. I'm running about 9.2:1 on 91 octane, non-intercooled for now (water injection though) with 15 psi of boost through an intake that flows 305 per port and heads that flow 290/220 @ .600 (and have very good midlift flow and a very good I/E ratio across the board)-- so that 15psi of boost doesn't mean I'm trying to shove too much air through crappy heads/intake.
Given that supercharger cams are longer duration and "nastier" than turbo cams, having the compression ratio too low means poor overall efficiency when off-boost. That's OK for a race car but a bad move for a street car IMO. Better to keep the compression up some and the boost down a little to maintain off-boost mannerisms. Granted, you will sacrifice some of the all-out HP and boost potential that you could have with a lower static CR and more boost but the engine will be much more pleasant when off-boost with the higher CR.
Like anything, it's a series of compromises, and for a street car with a centrifugal going more compression and less boost is the way to go.