2007-2011 Polaris IQ Snowmobiles Service Manual, Page 120Get this manual
General Information Compression Ratio Example
Bore6.5cm Stroke6.0 cm Removed cc's1.299cc's IHV17.1ccStroke (6.0cm)(Displacement (199.098) 2.54 Displacement3.1416 (PI) 42.25 (Bore squared) 6.0 (stroke)= 199.098cc Displacement199.098cc R= 17.1199.09817.112.643 Full Stroke Compression Ratio To calculate the Effective Compression Ratio, substitute the exhaust port height for the stroke in the formulas above: Exhaust2.95cm (exhaust port height is 29.5mm) Effective Displacement3.1416 (PI) 42.25 (bore squared) 2.95 (exhaust port height cm)= 97.89cc Effective Displacement97.89cc Effective Compression Ratio17.1 (IHV cc)97.89 (Effective Displacement cc)17.1 (IHV cc)6.725 Effective Compression Ratio6.725 In order to increase the Full Stroke Compression Ratio to 13.6, how much material do you need to remove from the cylinder head? You know that:IHVDisplacementIHV, and you want to find out IHVDisplacement199.098cc, and we want to13.6, so then IHV (desired)Displacement (199.098cc)(13.6)= (12.6) IHV (desired)15.801cc desired IHV to have 13.6:1 Full Compression Ratio I= 0.01186 inches To find out how much to machine off, multiply the number of cc's you need to remove by the number of inches to remove per ccThickness to remove(0.01186) 1.299cc0.015"