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  #16 (permalink)  
Old 02-14-2011, 01:42 PM
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When dealing in compression x power shown on a curve for a certain fuel, it violently curves up around 8.8:1 to 11.5 compression. Indicating a possibility, that there , lies the best compression ratio to extract power from a fuel source.

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  #17 (permalink)  
Old 02-14-2011, 04:04 PM
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Quote:
Originally Posted by MouseFink
5738 CC engine displacment
5738 / 8 = 717.25 CC cyl. vol.

717.2 CC / 85 CC chamber vol. = 8.44 : 1 CR

Assuming (without actual measurment):
64 CC combustion chamber vol.
+9 CC gasket, reliefs, deck vol.
+12 CC dish vol.
_______
85 CC total chamber vol.
That engine could run good on Cool Aid.
As usual, your wrong.

You did the math incorrectly. You have a 717.2cc cylinder volume and an 85cc chamber/gasket/deck height volume, but you forgot one step,... you have to add together the cylinder volume and the head chamber volume to get total volume, then divide by chamber volume.

So, 717.2 plus 85 equals 802.2, 802.2 divided by 85 equals 9.43 to 1 compression ratio...using the volume numbers you proposed for each component.
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Old 02-14-2011, 09:19 PM
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Quote:
Originally Posted by ericnova72
As usual, your wrong.

You did the math incorrectly. You have a 717.2cc cylinder volume and an 85cc chamber/gasket/deck height volume, but you forgot one step,... you have to add together the cylinder volume and the head chamber volume to get total volume, then divide by chamber volume.

So, 717.2 plus 85 equals 802.2, 802.2 divided by 85 equals 9.43 to 1 compression ratio...using the volume numbers you proposed for each component.
Wow! You lost me at "SO", Can you speak english. LOL
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  #19 (permalink)  
Old 02-14-2011, 10:46 PM
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To put it simply, the compression ratio is the ratio between the cylinder volume w/the piston at BDC compared to the volume w/the piston at TDC. Or the ratio of the largest you can make the volume of a cylinder to the smallest volume you can make the cylinder.

As ericnova72 correctly pointed out, this ratio includes the combustion chamber volume in both sides of the equation.

To help visualize this, a simplified scenario might be:

Total volume at BDC of 1000cc
Volume at TDC is 100cc

The ratio of the smallest volume (at TDC) to the largest volume (at BDC) is 10:1.

Personally, I use an online calculator whenever possible. But if you want or need to do it longhand, TI has posted the formula in easy to understand language, HERE, post #8.
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