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Discussion Starter · #1 ·
From the old post...if any one wants to know.

Bore is the diameter of the piston.

in our case the calculations are the following..

b - bore length inches
PI - 3.14....
s - stroke (the travel length of the piston) inches


displacement = ( b/2 )² * PI * s * 16.387064 cc3/inch3 + dome space in cylinder - dome from piston(very small).


ex: 34mm bore piston ~ 1.33858268 inches with a 2.0 inch stroke..

(1.33858268 / 2)² * PI * 2.0 *16.387064 = 46.2 cc + combustion area dome(~5cc) - piston dome(~1.5).

this calculates a 50 cc setup. 34mm piston.
 

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Wow, in class they never taught us the part about "16.387064 cc3/inch3 + dome space in cylinder - dome from piston(very small)", wonder why? The formula I was taught is:

( b/2 )² * 3.1416 * stroke * number of cylinders.

For bore and stroke, if you plug in metric measurements, that will give you Cubic Centimeters. If you plug in standard measurements, that will give you Cubic Inches.

For a cag, bore is 40mm and stroke is said to be 32mm (I haven't confirmed this yet) which would equal 40.2cc. With the big bore (44mm) it will be 48.7cc. With the big bore and FCS crank (35mm stroke) it will be 53.2cc.
 
G

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numbers game

The only time the combustion chamber volume and piston dome volume matter is when you are trying to figure out the compression ratio.

And if you don't know the chamber and dome numbers, just get out your handy burrette and cc the thing.
 
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