2. Modification of the distribution diagram

2.1 Shimming variation

Shifters represent the first step in variable valve timing. This is due to both the technological "simplicity" and the multiple benefits in terms of pollution, fuel economy, performance and combustion stability at low engine speeds.

The function of the camshaft shifter is to vary the timing of the camshaft(s) in relation to the crankshaft. Valve lift and spread remain constant. In other words, placed on the intake and/or exhaust camshafts, its principle is to vary the opening moment of the valves, without modifying the total opening time. Of course, the closing moment is modified in the same direction.