This necessitated the fitment of larger diameter intake runners (37 versus 35 mm).

When the piston accelerates downwards, the pressure at the output of the intake runner is reduced.

The traditional solution has been to tune the length of the intake runner for a specific engine speed where maximum performance is desired.

In some engines the intake runners are straight for minimal resistance.

First, two discrete intake runners with different length are employed, and a butterfly valve can close the short path.

A variable tumble control system creates air tumbles in the intake runners at low rpms for better mixture.

The flaps are smaller than the intake runners and therefore allow air to pass around them even when "closed".

The system uses two separate intake runners per cylinder, one being equipped with a butterfly valve that can either open or close the runner.

The swirl makes for more efficient combustion, and is due to the asymmetric nature of the airflow with one intake runner closed.

Since the fuel passes through the intake runners (like a carburetor system), it is called a "wet manifold system".