Compression
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Club Member
Joined: Feb 2008
Posts: 11,483
Likes: 39
From: Passaic County, NJ
Compression
Is there a compression gauge that will tell you your engine is "x:1" or is it derived through using math?
I know there are compression gauges that tell you how much pressure there is in each cylinder.
I know there are compression gauges that tell you how much pressure there is in each cylinder.
Not that I am aware of, but I have been wrong once before. I checked and found a couple of sites that give you some help on the formulas to figure this.
http://www.csgnetwork.com/compcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.kb-silvolite.com/calc.php?action=comp
http://www.gtsparkplugs.com/CompRatioCalc.html
As far as turning your xxx lpounds of pressure into compression ratio, I dunno
http://www.csgnetwork.com/compcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.kb-silvolite.com/calc.php?action=comp
http://www.gtsparkplugs.com/CompRatioCalc.html
As far as turning your xxx lpounds of pressure into compression ratio, I dunno
Tourer
Joined: Dec 2009
Posts: 339
Likes: 0
From: Northern BC, Canada
I'm willing to bet that the only way to determine ratio is through the math: Displaced volume/combustion chamber volume. The gauge just tells you how well your rings are sealing and holding the pressure that results from the compression stroke.
However, I too have been wrong.
However, I too have been wrong.
Banned
Joined: Jul 2009
Posts: 3,719
Likes: 1
Ditto, compression ratio is just that... A ratio between the open cylinder volume, and the volume remaining in the combustion chamber after the piston is at full top dead center. Ratios are mathematical equations. No gauge can give you that ratio.
Road Master
Joined: Feb 2010
Posts: 1,210
Likes: 1
From: LI, NY
Why the need to know compression ration?
The math is easy to do. Get the formulas off the net. The hard part is measuring the volume of the combustion chamber due to the irregular shape of the combustion chamber area of the head. Bore and stroke is provided by the manufacturer.
Also volume is effected by if the piston is flat or not. Some pistons have raised portions, some pistons have recessed area's for valve clearance. Those area's are difficult to measure for the average person to do. One could do volume displacement tests on the combustion chamber and non flat cylinder heads to get the numbers to do the math.
But one would have to tear down their engine, or get duplicate parts to avoid an engine tear down to take the measurments.
I would think that if one was buying a high performance head or pistion they should be able to provide the volume measurements so the owner/builders could determine the new compression ratio of the new build.
The math is easy to do. Get the formulas off the net. The hard part is measuring the volume of the combustion chamber due to the irregular shape of the combustion chamber area of the head. Bore and stroke is provided by the manufacturer.
Also volume is effected by if the piston is flat or not. Some pistons have raised portions, some pistons have recessed area's for valve clearance. Those area's are difficult to measure for the average person to do. One could do volume displacement tests on the combustion chamber and non flat cylinder heads to get the numbers to do the math.
But one would have to tear down their engine, or get duplicate parts to avoid an engine tear down to take the measurments.
I would think that if one was buying a high performance head or pistion they should be able to provide the volume measurements so the owner/builders could determine the new compression ratio of the new build.
Thread Starter
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Club Member
Joined: Feb 2008
Posts: 11,483
Likes: 39
From: Passaic County, NJ
@all:
I did search pretty thoroughly before asking. I found quite a few sites that have a form set up and all you do is enter pertinent values.
That's where having the heads cc'd comes in, right? Gives you one piece of the equation.
I appreciate your responses. Thanks.
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