The flaps are fully open during higher load conditions to maximise volumetric efficiency and power output.
The swirl flaps are a poor design, they are prone to failure.
When the swirl flap breaks, the debris falls into the engine, either sticking in the valve port and jamming it open, causing the piston to collide with the valve, or falls into the cylinder itself causing the piston and head to become damaged.
For BMWs pre 2003 53 the swirl flaps will be a 22mm size. For BMWs after 2003 53 you will need to remove the manifold and check the size of the swirl flaps. You can also purchase both sizes and return the unused set under our 1 year no quibbles return guarantee.
I6automotive has manufactured a cost effective solution. Blanking plugs that will replace swirl flaps and leave your engine running just as it was before.