Does a Compression/Horsepower Ratio Exist?

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Jan 8, 2008 | 11:13 AM

#16

rskrause

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Joined: Dec 1969

Posts: 10,745

From: Buffalo, New York

Quote:

Originally Posted by Stoopalini

Thanks Rich.

I assume the chart numbers are percentage of increase while the axis numbers are compression ratio. If so, assuming the stock CR is 10.5:1, I dynoed 287RWHP with that CR, and trimming .025 will net me close to 11:1, I can expect an increase of about 1%, or 2.8RWHP?

If I'm reading that correctly, then I don't see what all the arguing is about when it comes to using different head gaskets?

Thanks again for posting up the chart,
Thomas.

That is how I read it, and Vizard knows his stuff. Increased CR may also improve throttle response and mileage, but I can't see an increase from 10.5 to 11:0:1 making a big difference.

Edit: One thing that applies is that the bigger the cam is, the greater the difference with a change in compression. But a half point is still very small. On my BBC alcohol bracket motor, we needed a thicker head gasket that dropped the CR fro ~13.7 to ~13.0:1. It made 4hp MORE with the lower CR. Now, the test conditions (air density) was better when it made more hp, so it is not a scientific experiment. But it should give you the idea that the difference is small. The car runs the same at the track, BTw.

Rich

Last edited by rskrause; Jan 8, 2008 at 11:34 AM.