How much power is a full point of compression worth...

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Nov 28, 2003 | 03:12 PM

SPANKY LS1

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From: Seneca, SC

How much power is a full point of compression worth...

How much power is a full point of compression worth in a real world application. For example:

A 450rwhp H/C car at 11:1 would be a ___ rwhp car at 12:1? 13:1?

Nov 28, 2003 | 03:15 PM

Phil99vette

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From: Port Tobacco, MD

3-4% is the rule of thumb I have always used.
Phillip

Nov 28, 2003 | 04:35 PM

Quickin

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Quote:

Originally Posted by Phil99vette

3-4% is the rule of thumb I have always used.
Phillip

What if your going the other way and you want to find out how much power a motor is down?

My leakdown tests showed as high as 45% leakdown, considering an average leakdown of 25-30%.

How much would a 500 RWHP N/A motor be down?

Nov 28, 2003 | 04:59 PM

NA$TY-TA

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From: San Antonio, TX

Or going the other way on purpose...?? But adding cubes.. Going from a stock compression 346ci to a 8.5:1 383ci motor..??? Im not really worried about losing the power cause im adding more boost... just wondering.
Kyle

Nov 28, 2003 | 10:23 PM

silverbeast

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From: Ruffin,N.C.

I have been wondering the same thing. a friend of mine blew his motor up and went from stock bore 11.5-1 comp, to 60 over flat top (not sure of what final comp. ratio he ended up with ) with the same set of heads and everything. the heads were shaved a little im sure after the blow up but not sure how much. i was wondering which one would make more power? does anybody know?

Nov 29, 2003 | 09:47 PM

z98

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Um, adding boost completely screws up any calculations anyone could hope to make about hp to compression ratio calculations.

Nov 30, 2003 | 01:38 AM

pekkaz

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If the cam is not too large for the original compression then theoretically, according to D.Vizard How to Build Horsepower Vol. 1 the gain is

10:1 -> 11:1 1.5%
11:1 -> 12:1 1.3%
12:1 -> 13:1 1.2%

A 450rwhp 346 has quite a radical cam so the suggested 3-4% could probably be realized going from 11:1 to 12:1 due to getting the dynamic compression better. No personal experience about this though.