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?

 

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?

 

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

 

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?

 

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

 

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.

 

Car Craft tested this idea and proved it was 3-4% per point, not less than 3% in the 9-12:1 range

 

Can you tell how much compression you're down by a leakdown test?

Then figure how much HP you're down?