Compression Ratio
Is calculated as follows (fill in the blanks)
Bore = Orig Bore Size + Clearance + Overbore amount
| ___________ | with | ____________ | clearance on | ____________ | overbore |
| Original Bore i.e. 4.360 | piston clear in .000 i.e. .0025 | amt of bore i.e. .030 or .040 | |||
| __________ | + | __________ | + | __________ | = | ___________ |
| bore |
Swept Volume in Cubic Centimeters (cc’s)
Bore 2 X 12.8704 X Stroke 12.8704 = .7854 x 16.387 (# of CC per CI)
| ________________ | x | 12.8704 | x | _____________ | = | ______________ |
| Bore x Bore | Stroke | Swept Volume |
_________________ X 12.8704 X _______________ = ________________
Clearance Volume in Cubic Centimeters (cc’s)
| Chamber CC | + | Deck Volume | + | Gasket Volume | + | Piston(relief or dome)Volume | = Clearance Volume |
(See "A" below) + or - number
| _________ | + | _________ | + | ___________ | + | ____________ | = | ______________ |
| chamber cc | deck volume | gasket volume | piston volume +/- | clearance volume |
"A" - Deck volume is the amount of additional clearance above the block and must be calculated just like swept volume; except instead of using stroke length you use clearance amount.
| Bore2 | x | 12.8704 | x |
____________ | = | _____________ |
| i.e. .015 or .025 |
Knowing all these numbers now … you can fill in this formula
| Compression Ratio | = | Swept Volume | + | Clearance Volume | / | Clearance Volume |
| ___________ | = | __________ | + | __________ | / | ________ |
Clearance can be backed into by reversing the formula above to
Clearance volume =Swept Volume / Comp Ratio -1
| __________ | __________ | __________ | ||||
| Clearance Volume | = | Swept Volume | / | Comp Ratio - 1 |
EXAMPLE
Bore = Orig Bore Size + Clearance + Overbore amount
| 4.036 | with | .0025 | clearance on | .030 | overbore |
| Original Bore i.e. 4.360 | piston clear in .000 i.e. .0025 | amt of bore i.e. .030 or .040 | |||
| 4.036 | + | .0025 | + | .030 | = | 4.3925 bore |
Swept Volume in Cubic Centimeters (cc’s)
Bore 2 X 12.8704 X Stroke 12.8704 = .7854 x 16.387 (# of CC per CI)
| 19.294056 | x | 12.8704 | x | 3.85 | = | 956.04 cc |
| Bore x Bore | Stroke | Swept Volume |
Clearance Volume in Cubic Centimeters (cc’s)
| Chamber CC | + | Deck Volume | + | Gasket Volume | + | Piston(relief or dome)Volume | = Clearance Volume |
(See "A" below) + or - number
| 96 | + | 3.73 | + | 11.4 | + | 4.7 | = | 115.83 |
| chamber cc | deck volume | gasket volume | piston volume +/- | clearance volume |
"A" - Deck volume is the amount of additional clearance above the block and must be calculated just like swept volume; except instead of using stroke length you use clearance amount.
| 19.294056 | x | 12.8704 | x |
.015 | = | 3.73 |
| i.e. .015 or .025 |
Knowing all these numbers now … you can fill in this formula
| Compression Ratio | = | Swept Volume | + | Clearance Volume | / | Clearance Volume |
| 9.25 | = | 956.04 | + | 115.83 | / | 115.83 |
Clearance can be backed into by reversing the formula above to
Clearance volume =Swept Volume / Comp Ratio -1
| 115.83 | = | 956.04 | / | 8.25 |
| Clearance Volume | = | Swept Volume | / | Comp Ratio - 1 |