[Bmw doubles]

Originally Posted by Stà¼ck

Bmw doubles I hope your dyno session has gone well, and you put down the numbers you were looking for.

Alex and I have been racking our brains for a bit wondering what was going on with my excessive wastegate duty cycle to hit boost requests. We've been inching it up, but again the WGDC was too high for requested boost.

I'm at 52% WGDC to see 10-12psi. Where as the norm (per collected peer data) on a Pure Stage 2 at that WGDC should be 20-24psi.

I've exhaustively tested for boost leaks, pressurized the entire system with smoke and shop air, done testing hot and cold... pretty much ran out of places to point a finger.

A few days ago I noted my waste gate felt a bit hard to articulate by hand, well... with a long hook tool as you can't reach it from the top on F10.

It occurred to me with my recent acquisition of a F25 X3 35i for my wife I had an identical set of stock hardware to test and switch parts on.

[IMG]http://i1279.photobucket.com/albums/...pstqu5obrx.jpg[/IMG]

Long story short after lots of testing and part swapping I got out a hand vacuum pump and connected it to the X3's wastegate vacuum actuator. It started moving upon application of vacuum, and reached fully closed with 7Hg applied. On my F10 the wastegate doesn't even start to move until 7Hg, and takes 12-15Hg to reach fully closed.

I knew at this point this afternoon one of two things were going on. Either the wastegate actuator was sticky, or the wastegate arm coming out of the turbo housing was.

Jacked the F10 up and pulled the underpaneling for access. Spun the outer nut off the wastegate rod and reapplied vacuum. Rod now pulls in smoothly like the X3, reaching fully closed at 7Hg.

Reached up with my hand and tried to articulate the wastegate arm on the turbo. It's binds in place with any axial load.

Well shit...

After much debate I decided to lube the arm where it goes into the housing with the highest temp/sticky oil I have, Lucas gun oil. It made it a teeny bit better after a few drops and working it back and forth by hand dozens of times. It still binds under axial load though. The rod is pulling at with a axial load, as is the exhaust gas pushing against the wastegate seat.


Not sure what to do at the moment, but this finally explains the excessively high WGDC, as the DME is sending much more PWM signal to the vacuum solenoid to get the damn thing to close than it should have to.

Wow great discovery with the actuator. I saw many videos about adjusting the arm and thought I too could have either a loose position between the two nuts that adjust the arm(infamous wastegate rattle fix) or the solenoid was going bad. Then the dyno happened yesterday! And those 2 possibilities are not robbing me of power. I might be able to get slightly better response with a fine adjustments to the actuator arm. I'll try the lube technique like you mentioned.

I am about to put up some video and pics and dyno numbers. Lots of game changing discoveries for us PWG folk. Not to spoil it yet, but a quick review is we made more power with less torque and held more PSI to redline. Alex totally reversed engineered BMW's code and found the limiters stopping F10 N55's from making the same power as our little brothers the F30 (watch out boys). @stuck you should be making well over 400whp with PS2 and MP stage 2 on your N55