The return of Swirl Flaps!

Thought your N47 swirl flaps were completely reliable? Then think again… Words and photography: Andy Everett

 

Whilst the swirl flaps in the old M47/M57 diesels gained a well-deserved reputation for failure and subsequent engine damage, BMW worked hard to redesign the system on the later N47 that arrived in late 2007. On the previous engines, the swirl flaps were steel and ran on their own pivots with an external operating rod. The pivots could fatigue and break allowing the steel flaps to fall into the combustion chamber but after 2004 (and certainly for the first E90s and 520d E60s), the flaps on M47s were made bigger to make it impossible for them to fall down the intake runners.