E92 automatic xdrive drivetrain 'pulsing'

Narcosis

Corporal
Dec 14, 2016
119
64
0
Hudson, WI
Ride
E92
The car is a 2010 E92 xdrive automatic with a 6hp19z per my local BMW dealer. Turbos are RB Next Gen Plus with hardware in place to support them. Fueling is a new(ish) HPFH, fuel-it stage 3 LPFP, MMP port injection & full e85. XHP stage 2 flash for the tranny.

I've been slowly turning up the power with my tuner (Wedge), and last week noticed the car "pulsing" during a 3rd gear logging pull. Initially I thought it might be tune related, however the logs look smooth as silk. What I feel while accelerating can probably be best describe as the throttle plate closing and opening a bit, every second or two. The logs tell me that's not occurring.

This is probably a bit vague, but I'm not a drivetrain guy by any stretch of the imagination - and this is my first automatic. If an automatic tranny starts slipping, will it act similar to a manual clutch slippping? I believe the tranny locks up somewhere along the line to take some of the load off the torque converter.

Any AWD guys care to chime in with anything even remotely related? I'm pretty pleased with the power being made, but am a bit gunshy about using it. Haven't dyno'ed or taken it to the track yet, virtual dyno says mid 500's hp and just over 600 tq - probably pissing the tranny off a bit. No transmission cooler yet, either.
 

Cheezy

Lieutenant
Nov 7, 2016
610
223
0
Toledo Ohio
I have a similar issue I described to my tuner as "...seems to only happen when im cruising with just enough pedal to maintain speed but not accelerate, and it doesnt do it all the time, just when theres no load on the engine, like going down hill or a flat road. It doesnt happen when im completely off the gas or accelerating. It feels like i get like an extra 50rpms like every other second. I thought maybe the throttle was weird but i reset those adaptations with no change. Its just a weird drivability comfort issue." I did get a log of the issue, at the end of this cruising log you can see it.
 

Narcosis

Corporal
Dec 14, 2016
119
64
0
Hudson, WI
Ride
E92
To close the loop on this, the issue appears to have been suspension related. The right front KW strut was shot, after replacing both front struts the issue is gone. My tuner suggested more than once that what I was experiencing may have been loss of traction, I'm now on board with that. After the new struts were installed I did a few logging runs for a new map, no issues. Well, except that it appears the car needs upgraded coils.