Displacement

[Youth Gone Wild]

The initial message has been deleted from this topic.

[GreenV8S]

Why not simply swept volume? You can ignore compression ratio, that doesn't affect the displacement.

[dilbert]

I think "Displacement", refers to how much liquid/gas would be displaced in a complete cycle of the engine. From a simple perspective, displacement is just "swept volume", and I suspect that it does not include the practical dynamics of exactly when the valve events occur.

Changing the compression ratio affects the maximum possible volume of the cylinders, but by very little.

If one ignores any leakage issues, the compression can be calculated as the volume in the cylinder when the inlet valve closes divided by the volume when the compression cycle is at it's furthest travel. If one halves the volume of the compression space the compression ratio doubles.

Half of not is still not a lot, but the equivalent compression ratio is doubled, and that's one hell of a whack.

Edited to add;

I think there's a logarithmic/exponential thing going on here.

>> Edited by dilbert on Wednesday 4th May 22:02

[Annodomini2]

Have a search down this forum, its been mentioned before.

[deltafox]

Displacement is the swept volume of the cylinder minus its compression volume multiplied by the number of cylinders present.

Compression ratio can be calculated by the following simple equation: VS+VC over VC

Vs= swept vol
VC= clearance volume (take into account dishes in pistons and valve cutouts etc).