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Old 08-15-2006, 05:51 PM   #1
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Default compression ratios

Being,s i got an auto with 9:1 compression opposed to 9.4:1, how much more boost can they take over 9.4,s, ? - as ive heard on numerous occasions that the 9:1 ,s are better suited to F.I.
Just a ball park fig for comparison- as i,m running a "fairly aggressive "timing map with no sign of det/ping- just wandering how far to go with advancing the timing
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Old 09-13-2006, 12:52 AM   #2
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12-14deg made my n/a happy on pump gas. I ran 91-93. To much advance (or retard) and the peak of combustion isn't at the optimum crank position for maximum power.

-LAZ
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Old 09-13-2006, 12:57 AM   #3
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Quote:
Originally Posted by rockdoc View Post
ive heard on numerous occasions that the 9:1 ,s are better suited to F.I.
You mean boosted engines?
Forced Induction?
Fuel Injected?

I read it wrong the first time around.

Lower compression is less prone to detonation then higher compression. Your cramming more air/fuel in the same space and high compression can ignite it early.

-LAZ
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Old 09-13-2006, 03:14 AM   #4
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yeh- boosted , forced induction
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Old 09-13-2006, 09:45 AM   #5
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You also need to consider block and head thickness. I've seen manual trans 1.6s running near 9:1 static compression because the block and head thickness is on thick side of the tolerances. For example you'll see one guy run 18* advance without knock, while another can't run any more than stock. It's all about tolerances. - rob
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