View Single Post
      08-25-2012, 09:39 AM   #15
Major General
doughboy's Avatar
United Kingdom

Drives: 2016 M6 Gran Coupe LCI
Join Date: Jan 2009
Location: UK - Midlands

iTrader: (2)


Sorry to waffle, but i've spent time (and money) on this...

Mine has always suffered from a recurring ticking rattle on warm starts which goes in about a minute.

I've had it adjusted twice properly with a hand vaccum pump (2nd time just this week) with DPs off.

The Mr5 methods is flawed IMO in that he assumes the ECU can control each wastegate separately, this is not the case, there are 2 solenoids, but the output vaccum lines are paralleled up, so there is only 1 vaccuum for both turbos. It is thus very important that both wastegates close exactly the same amount for any given vacuum.

If you over-adjust one actuator only, then that turbo will produce more boost than the other for a given vacuum level. This extra boost will heat up that turbo more and will actually fight against the other turbo's output.

BUT - in practice it seems that the rear turbo linkage wears more (hotter maybe?), in both cases on my car an extra 1/2 turn on the shaft was required on the rear turbo only to get full closure at the specified 200mbar vacuum. The front one was fine. So as long as you are just winding out slack to get back to the correct operation you are ok.

This tightening also fixes the rattle for me, until it wears again. The wear on mine (and all probably) is the wastegate pivot in the turbine housing NOT the actuator arm end pivot. This is as confirmed by Turbo Dynamics who I had a chat with. So ultimately, the shaft will be so loose in the housing it will bind / jam causing under/over boost codes.

Also of concern is the method of adjustment in Mr5s post, the actuator rod is FIXED to the vaccum diaphragm, it does not rotate, so turning it will presumably break / loosen something? We tried to turn mine and they wouldn't budge easily.

The correct way to adjust it is to loosen the lock nut at the pivot end, take the shaft eye off the wastgate arm pin, turn the eye half a turn and put it back on the wastegate arm, then tighten it up.

BTW you can't put any grease anywhere as the temps are so high it will just burn off, the wastegates and linkages have to run completely dry. The turbine housing runs at about 1000degC, so watch anything else too. The suggested copper washers would melt at 905degC!
E90 330i 6MT gone. E91 335i 6MT gone. AMG E63 Estate gone. M6GC current...

Last edited by doughboy; 08-25-2012 at 10:01 AM.