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Unread 2012-12-30, 01:07 PM   #1
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Default Compression ratios and f/i

Everybody knows boost pressure increases c/r. and if you visit zealautowerks.com/bseries.html to play around with different setups, itll even tell you by how much. But one thing it doesnt take into account is turbo size. That doesnt make sense to me. Knock occurs when the c/r causes a big enough increas in heat that the a/f mix combusts prior to the spark plug firing, right? Assuming theyre both running at the same efficiency why would a small turbo at 20 psi cause the same c/r as a much bigger one at the same psi when the bigger turbo is pushing more cfm of air? It doesnt, right?
Maybe its a stupid qustion, but I couldnt find anything on google.
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Unread 2013-01-25, 05:59 PM   #2
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Nobody? lol
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Unread 2013-01-25, 06:21 PM   #3
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Static compression ratio, what zeal calculates does not translate directly into cylinder pressure.

Knock limit and cylinder pressure are closely related. More specifically, the cylinder pressure profile and the cylinder pressure peak.

There is a hell of a lot more to the knock limit of an engine than just the static compression ratio.

Also, as you have already stated, two different sized turbos running at the same boost pressure will almost always have different flow rates. Think about it like this. More air requires more fuel. More air/fuel charge equates to more cylinder pressure.

Temperature also plays a critical role on knock limit as well.

In short, ignore that part of the calculator because it is useless rubbish.
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Unread 2013-03-24, 09:44 AM   #4
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Unread 2013-04-11, 01:24 AM   #5
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Your trying to get too complicated with it.
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