Variable Intake System

General 

Today's modern car engines often utilize systems with variable length of the intake manifolds.

In older engines with fixed lengths, the length had to be adapted to a certain specific engine speed range.

Today's system gives greater flexibility as well as additional torque without any costs in the form of, e. g., fuel consumption or emissions.

In the variable intake system, there are two actuators with associated throttles to change the length of the intake manifolds. These are:

• Actuator variable intake manifold, upper (6/139)
• Actuator variable intake manifold, lower (6/140)

The primary throttle is activated at engine speed over approx. 4800 RPM and the secondary throttle is activated between approx. 3800 RPM and 4800 RPM (applies at + 20 °C).

Different throttle combinations: 

• Position 1:  Both throttles are closed at engine speeds lower than approx. 3800 RPM.
• Position 2:  The secondary throttle opens at approx. 3800 RPM and this shortens the length some more.
• Position 3:  Both throttles are fully open to minimize the length at higher engine speeds (over 4800 RPM).

The valve for variable intake is controlled by the engine control module (ECM) (4/46).

The actuators for variable intake function can be activated and the function for variable intake can be diagnosed by the engine control module (ECM).