N55 pulsing, oscillation, or fluctuation of boost

[sjk9671]

Hey guys,
I need a little help diagnosing an interesting issue I have with the car. First details: 2012 135i N55 DCT with JB4 and BMS intake. The issue I am having is, I seem to be getting a pulsing, oscillation, or fluctuation of the boost. Here is how I notice the issue:

1.) put the DCT in a higher gear like 5 or above
2.) go around 30mph and give it about 60% throttle on a hill

This will result in a decent load on the engine and forcing the turbo to build pressure up and hold it, I can hear the boost (via the BMS intake) fluctuating up and down and this results in the engine sound doing the same thing. It would resemble the patter on a sine wave. Almost as if I was on and off the gas with my foot. I can do this with JB4 on Map 1 (my usual map) as well as off (Map 0).

Should I be looking at a boost leak or maybe an issue with the diverter valve? Wastegates? Or maybe the boost controller? If I go WOT I don’t seem to notice it as much if at all. Car is CPO and mi is at 48K.

Thanks for looking!
Steve

[c_ozanich]

You're default wastegate position needs adjusted. Typically its default is set to 80, try changing that to 20 or 30. this will cause a slight bit more turbo lag but you can slowly work back up to 80 to find out what optimal set point is for your car. Mine is at 50 and running great

[sjk9671]

Originally Posted by c_ozanich

You're default wastegate position needs adjusted. Typically its default is set to 80, try changing that to 20 or 30. this will cause a slight bit more turbo lag but you can slowly work back up to 80 to find out what optimal set point is for your car. Mine is at 50 and running great

I would think that have effect only when the JB4 is on right? I can reproduce the issue with JB4 off.

Steve

[The Wind Breezes]

If you didn't touch anything on the hardware side I have difficulty imagining your issue is not caused by the JB.

[sjk9671]

Only thing was the BMS intake. I don't really know what the symptoms of a boost leak look like. I was thinking the extra boost could have sprouted a leak somewhere? I can reproduce the issue even with the JB4 in map 0 (off).

[dh58]

Did you start having this issue once you upgraded to 31.5?

If so it might be an issue that I and others have had. Try lowering menu 12 to 2k and see if it stops.

[sjk9671]

Originally Posted by dh58

Did you start having this issue once you upgraded to 31.5?

If so it might be an issue that I and others have had. Try lowering menu 12 to 2k and see if it stops.

Not sure I follow? Are you referring to the firmware version? I am not running ISO.

[e36addict]

My car does this. Always has. I've learned to ignore it...

[Mernardi]

Run logs and post them at N54tech. BMS should be able to help you track down the issue.

[c_ozanich]

Originally Posted by sjk9671

I would think that have effect only when the JB4 is on right? I can reproduce the issue with JB4 off.

Steve

mine did same thing, its caused by "wastegate rattle" issues; you can use JB4 to correct it by adjusting the default position.

[Mike@N54Tuning.com]

It might be as simple as a JB4 setting. Post a log of the problem occurring in the n54tech support area and a BMS professional can help you double check things.

Mike

[sjk9671]

Originally Posted by Mike@N54Tuning.com

It might be as simple as a JB4 setting. Post a log of the problem occurring in the n54tech support area and a BMS professional can help you double check things.

Mike

Will do as soon as it stops raining here. All I would get now is wheelspin.

[Tony135]

Mine has done this forever. It's Jb4

[sjk9671]

Originally Posted by Tony135

Mine has done this forever. It's Jb4

Mine will do it even with JB4 off.

[Tony135]

Originally Posted by sjk9671

Mine will do it even with JB4 off.

Even if you leave JB4 off for a while? Mine usually stops as soon as I switch to map 0, but my friend had this issue too and it took about a day of being on map 0 before it stopped.

[sjk9671]

Originally Posted by Tony135

Even if you leave JB4 off for a while? Mine usually stops as soon as I switch to map 0, but my friend had this issue too and it took about a day of being on map 0 before it stopped.

Hmm, I haven't left it off for that long. Thanks for the info!

[sjk9671]

Originally Posted by Mike@N54Tuning.com

It might be as simple as a JB4 setting. Post a log of the problem occurring in the n54tech support area and a BMS professional can help you double check things.

Mike

Here we go!

http://www.n54tech.com/forums/showth...978#post411978

[greensto]

Mine starting doing this when I updated to version 31 on my jb4. I can also replicate it on Map 0. It is most noticeable in the lower rpm range on light/medium throttle from a standstill to 40 mph. (I'm n54 by the way). Haven't fixed it yet or adjusted my wastegate setting. Just on default settings at the moment.