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jwasbury jwasbury is offline
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Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,612
Quote:
Originally Posted by drmatera View Post
Stock compression is very inefficient, going to 8 or 8.5:1 on an engine that you plan on running .8 to 1.0 bar and stock timing will be very safe not to mention more efficient and powerful off boost for street driving.
Of course this is doable but not sure I agree with "very safe." Some modern forced induction cars run static compression ratios in the 8 - 8.5 range, and that's with water cooled heads (my '06 Mini Cooper S comes to mind). With the latest direct-injection technology we are seeing static compression ratios in the 9s, but again with water cooled, four valve heads with a centrally located spark plug. Add 12-14psi of boost to 8-8.5 static comp ratio and you're getting a pretty high dynamic ratio. With the high cylinder head temps that these 930s normally run I worry about detonation and melting down Ex$pen$ive pistons and cylinders.

I'd argue that twin plug ignition is a must at the higher static compression ratios and I would want EFI and knock sensing if I was spending my own money on it. If I'm spending someone elses money, then I say go for it and keep us posted on how it works out
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Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 07-21-2011, 09:33 AM
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