Szeleplökedés

Szeleplökedés, often translated as valve float or valve bounce, is a phenomenon that can occur in internal combustion engines. It happens when the engine's rotational speed becomes so high that the valve springs are unable to close the intake or exhaust valves quickly enough. As the camshaft lobe pushes the valve open, the spring's inertia prevents it from returning the valve to its seat before the next lobe in the rotation comes around to push it open again. This results in the valve "floating" or bouncing between open and closed positions.

The consequence of szeleplökedés is a significant loss of engine performance and potential engine damage. When valves don't close properly, combustion gases can escape the cylinder during the compression and power strokes, leading to a dramatic drop in power output and increased fuel consumption. More critically, if the valves remain partially open when the piston rises, it can lead to a collision between the piston and the valve, causing severe internal engine damage, such as bent valves, damaged pistons, and even cracked cylinder heads.

Szeleplökedés is typically observed at very high engine RPMs, often beyond the engine's designed redline. It can be exacerbated by worn or weakened valve springs, or by modifications that increase valve lift and duration without upgrading the spring capacity. To prevent szeleplökedés, engines are designed with valve springs that have sufficient strength and stiffness to counteract the forces at their intended operating speeds. Performance modifications often require stronger valve springs to handle higher RPMs and more aggressive camshaft profiles.