72 BMWcar
WORKSHOP WISDOM
Andrew Everett tackles the removal of the dreaded swirl flaps on
a 120d, and does some valuable de-coke work at the same time
Swirl f lap
solution
M
y recently-acquired 2006
120d has a few issues, and
one of them may be related
to the dreaded swirl flaps.
It was running on three
cylinders and sounding a bit sick, so one
of my first thoughts was that it might have
ingested a steel swirl flap.
The problems associated with the swirlflaps on the M47N BMW engine have
been well covered over the years, and
are no longer a mystery. These days the
simple advice is that, if your car has them,
then they must be removed and replaced
with blanks that can be easily and cheaply
sourced online.
Swirl flaps were fitted for emissions
reasons, and to alter torque characteristicsslightly. In practice, though, removing them
creates no discernable difference. With the
manifold off, remove the flaps, chuck them
in the bin and screw the alloy blanks in
their place, but keep the actuator fitted and
plugged in to fool the engine ECU. If you
remove the actuator and leave the plug for
it dangling, then the ECU will detect a fault
and illuminate the engine management