Engine Parameters Calculator


This data is used to calculate the compression ratio.
Maximum Air Intake Requirements CFM.

The Engine Parameters calculator is designed to assist with engine modifications by calculating various engine parameters. This calculator is not designed to estimate engine power or efficiency. It is designed to calculate the effect of some modifications. For instance, you may want to know the displacement of your engine after it has been bored .060 over, or after you replaced the crankshaft with one that has a longer or shorter stroke.

The calculator will use whatever data is entered. If there is insufficient data, some of the output objects will be blank, undefined, or infinity.

The calculator attempts to make a calculation each time an input object is changed. There is, therefore, no [Calculate] button.

Enter the number of cylinders, the bore, and the stroke of the engine. This information will be used to calculate the displacement. The bore is also necessary for the calculation of the compression ratio.
Number of Cylinders
Bore
Stroke
Inches
Centimeters
Millimeters

Enter the volume of the pistons and combustion chambers (in the heads). The head chamber volume is always positive. The piston volume is positive if it is dished, zero if it is flat, and negative if it is a dome piston. This data is used to calculate the compression ratio.
Head Chamber Volume
Piston Volume
Cubic Inches
CC

Enter the Piston Deck Height and the Compressed Head Gasket Thickness. The Piston Deck Height (also known as the "Installed Height") is the distance that the piston protrudes above the top of the block. It is negative if the piston top is below the top of the block. The total piston to head clearance is the Compressed Head Gasket Thickness - the Piston Deck Height. This data is used to calculate the compression ratio.
Piston Deck Height
Head Gasket Thickness
Inches
Centimeters
Millimeters

This section contains the results of the calculations. The displacement can be entered if you want it translated to other units, or if you want to calculate the Maximum Air Intake Requirements.
Displacement Cu In Liters CC
Compression Ratio :1    

Enter the Volumetric Efficiency and Maximum speed. The displacement can be entered above, or calculated. While you won't see the volumetric efficiency of an engine stated very often, a good guess will get you close enough to choose the correct carburetor or throttle body. Most stock engines have a volumetric efficiency of 75-80%. Modifications (intake manifold, cam, exhaust, porting & polishing, etc.) can bring this up to 80-85%. Really highly tuned engines can actually go above 100%, but this occurs over a very small speed range. Forced induction engines (turbocharger, blower, etc.) can go well above 100%. From this data, the Maximum Air Intake Requirements are calculated.
Volumetric Efficiency %    
Maximum Speed RPM    
Maximum Air Intake Requirement CFM Liters/Min