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Old 05-25-2006, 08:38 AM
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compression ratios

what factors contribute to my compression ratio and how do i figure it

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Old 05-25-2006, 02:53 PM
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Bore, stroke and combustion chamber volume.

increasing bore or stroke with the cv constant increases CR
increasing cv (piston change or head change) decreases CR

The exact numbers can be calculated by mathmatically computing the volume of the cylinder when @ BDC vs @ TDC adding in the cv at each, Remember planar Geometry? pi R <sq> x pi R <sq> x H <stroke> Do all calculations in the same measure, cc volume is usually measured in cc so use metric measure for bore and stroke. The ratio of BDC volume to TDC volume is your CR :1

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Old 05-25-2006, 08:44 PM
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here is a good web site to figure all that type stuff just put in your numbers.
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Old 05-26-2006, 11:08 PM
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King, this can be an intimidating subject. I'll try to simplify it for you. Static compression ratio (as opposed to dynamic compression ratio) is the ratio of air/fuel volume taken in as the piston descends compared to the air/fuel volume when the piston is at top dead center. If the piston draws in 9 parts of mixture and compresses it into 1 part, the ratio is 9 to 1.

When you figure the mixture drawn in, you figure in all the volumes of all the crevices in the cylinder, deck, head gasket, valve eyebrows or other configuration in the piston and combustion chamber.

When you figure the volume that all this mixture is compressed into, you figure all the volumes except the cylinder.

Please read this post that I wrote for another forum. It should explain it to you in detail. If you have further questions, please ask......
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Old 05-27-2006, 03:26 AM
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I used this from ChevyHiPerformance to do mine.
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