Intake Manifold, Function

Intake Manifold, Function




Section through variable intake manifold in cylinder plane
22 Variable flap (one variable flap for each cylinder)
A Intake air when variable flap opened (variable intake manifold switchover valve de-energized)
B Intake air when variable flap closed
C to engine

When the engine is started and at low engine speeds the variable flaps are open. The intake air flows along the shortest path and thus reaches the cylinder with low friction losses from the distributor volume.

At an engine load of more than 50% from approx. 1750 rpm up to approx. 3900 rpm the variable flaps are closed. The intake air must flow through the whole intake pipe. Its length is selected in such a way that the pressure waves, produced by the inducting pistons, arrive at the right moment at the open intake valves for the next induction stroke. The result is improved cylinder charge and thus an increase in torque.

At higher engine speeds (e.g. from 3900 rpm) the actuation to the variable intake manifold switchover valve is interrupted - the variable flaps open as a result of the spring force. Through the shortened route the pressure waves arrive in time even at higher rotational speeds before the closing of the intake valves to the combustion chamber.