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starting with the entered Stroke.
To raise your compression from 8.5:1 to 10.5:1, your engine
building shop would need to remove 0.098 inches of material from
the surface of your heads, thus reducing the overall chamber
volume and increasing compression.
Notice the answer to your mill amount question is given in
inches, 0.098 inches, but it's a simple press of a key to convert to
millimeters if necessary. If you press the
key, your calculated
mill amount of 0.098 inches is converted to about 2.48 millimeters.
Calculating Piston Speed
Piston speed is an important factor when building an engine,
especially if that engine is being built to run short distances at
wide open throttle such as drag racing. Piston speed is the speed,
typically in feet per minute, at which the piston moves up and down
within a cylinder.
As your engine's crankshaft rotates once, your cylinder's piston
travels two strokes (up one, and down one). The piston's speed is
not constant throughout its travel. It may go from 0 to 100 miles per
hour and back to 0 during a single stroke. However, if the piston
speed is too fast, the result can be disastrous for your engine.
With advanced math, you could calculate the exact piston speed at
any particular point in the crankshaft rotation. Fortunately, knowing
the average piston speed is all you need to calculate when you are
building your engine. Modern metal materials enable higher piston
speeds today, upwards of 3500 feet per minute.
For this example, your Stroke is 3.48 inches, and you want to
calculate the Piston Speed at 4000 RPM.
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