How is it determined how many cubic inches or liters an engine is?

Engine displacement is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle...

It's the volume contained in one cylinder at BDC, times the number of cylinders.

Thanks, I knew it was something to do with the cylinders, just wasn't sure what. My dad was wondering. Thanks.

Engine displacement is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle...

It's the volume contained in one cylinder at BDC, times the number of cylinders.

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don't they add in the combustion chamber volume too?

don't they add in the combustion chamber volume too?

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Isn't "combustion chamber" a synonym for "cylinder" in engine terms?

Edited July 26, 200619 yr by NOS2006

i think he meant the head where the valves are.

Displacement is a mathematical computation of bore x stroke x # of cylinders.

I have read more than once that it does not include combustion chamber volume (valve area above the piston at TDC/above the top of the bore.

Displacement is NOT the volume contained by the piston at BDC, as bathazar has already explained. Displacement is the volume displaced as the piston moves from bottom to top. As was previously explained, the head has nothing to do with it, it is strictly measured by bore, stroke, and number of cylinders.

Displacement = (Bore)^2 * Stroke * Pi * number of cylinders

Displacement = (Bore)^2 * Stroke * Pi * number of cylinders

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Is Bore the same as diameter or radius? If it's diameter, then...

Displacement = Pi * (Bore / 2)^2 * Stroke * number of cylinders

the reason the combustion chamber is not counted is because that volume never changes signifigantly while the engine is running. You don't get a change in the amount of air intake if you increase or decrease the size of the combustion chamber.

the reason the combustion chamber is not counted is because that volume never changes signifigantly while the engine is running. You don't get a change in the amount of air intake if you increase or decrease the size of the combustion chamber.

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In mathematical terms for displacement, the combustion chamber volume does not

change; therefore it drops out of the equation.

Displacement is: Cylinder volume, when the piston is @ BDC minus cylinder volume when the piston is @ TDC; this result times the number of cylinders.

From this equation you can see that the combustion chamber is not significant.

Re: Wikepedia definitions---- anybody can ammend them, without proof of

the correctness of the data! Take their definitions with a grain of salt!

Oh yeah! BTW, for rough calculations 1 liter = 61.43 cubic inches. So if you know a displacement in metric terms, multiply by 61.43 to get cubic inches. Vice versa,

if you know the size in cubic inches divide by 61.43 to get liters. Simple.

Edited July 26, 200619 yr by rkmdogs

Is Bore the same as diameter or radius?  If it's diameter, then...

Displacement = Pi * (Bore / 2)^2 * Stroke * number of cylinders

You are correct...my typo. It is the radius (half the bore) of the piston.