[The Ghost]

Originally Posted by mfish123

I had a 6MT 335i and just picked up a 2009 335i AT xdrive with IJE0S. I'm on Cobb stage 1+. I've logged with and without the Alpina flash and Alpina might help a little with the 3rd to 4th shift timing but unfortunately whether on the stock TCU flash or Alpina flash I have really bad negative timing in 5th gear. In fact whether I up or down shift into 5th manually or by using the gas pedal, and / or am cruising in 5th timing always goes negative in this gear. With standard throttle mapping its pretty easy to get high boost in 5th gear. I don't know why for the life of me 5th gear is plagued when other gears aren't. This is extremely annoying when on the highway and I give a quick stab of the throttle and the car downshift from 6th to 5th and has reduced power. Is this indicative of the typical flatlining?

Also, I had success on my MT with upping the load target and reducing boost limit multiplier so the actual load never even got close to the requested load. Its working well on the AT too! The side effect to this method is that it tends to exaggerate some of the existing overboosts. It may also be more a hair more prone to oscillations when making relatively small changes to WGDC base. I'm working on squashing those overboost.
A shame I have to go through such great lengths to get the timing back and now have a boost curve that needs massaging.

I'm going to tweak the scaling and values in the boost limit multiplier to get a flat boost request from 3,500 to 5,000 RPMs. I have the load requested around 210 in the midrange and the boost limit multiplier around 2.2 in the mid range MAF Req airflows and have rescaled it to correlate with the airflows at the RPMs I'm focusing on. A lot of trial and error needed here.


Alpina and OTS stage 1+ 4.02

Atrocious negative 5th gear timing with no timing corrections: http://www.datazap.me/u/mfish123/atr...ng-corrections

3rd and 4th gear just fine: http://www.datazap.me/u/mfish123/3rd...gear-just-fine

Alpina and lowered boost limit multiplier - (timing is intentionally set 1 - 1.5 degrees lower at high loads, on the below, as a safety net, in the midrange, while testing)

5th gear just fine: http://www.datazap.me/u/mfish123/boo...gear-just-fine

3rd to 4th gear: http://www.datazap.me/u/mfish123/boo...3rd-4th-gear-1

I'm not following your change, result, and conclusion of your boost limit multiplier test. Please summarize.

I raised mine in hopes of allowing more boost before throttle closures (raising the limit).

[mfish123]

Originally Posted by The Ghost

I'm not following your change, result, and conclusion of your boost limit multiplier test. Please summarize.

I raised mine in hopes of allowing more boost before throttle closures (raising the limit).

Short as possible answer (I tend to be wordy):

I believe the root cause of timing "flatlines" (low or negative timing without timing corrections showing up) is the direct result of actual load getting too close to requested load. For whatever reason 5th gear for me and apparently 4th gear for others seem to be more sensitive than other gears.

To fix this I've raised load to super high values and lowered the boost limit multiplier. Essentially I'm getting the load target (or maybe a better label would be load limit) out of the way but I'm still able to control boost, with the boost limit multiplier, and not have boost go to insane levels that it otherwise would with these high load targets.

More observations:

The boost limit multiplier seems to be a multiplier of load so if you increase load then you have to decrease boost limit multiplier to compensate and still hit the intended boost target. It has some dynamics going on where you get to a point where you set load so high that if you're limiting boost so much with the boost limit multiplier, that the load target on the logs will not be as high as in ATR. But then if you increase the boost limit multiplier while leaving load at the same high levles and re log then the load target logged will get closer to what you have in ATR and maintain that needed spread between load target and actual load to mitigate the timing flatlines. I also think there is some inherent taper built into the DME so you can't just set the boost limit multiplier to the same value in the midrange using this method (like it is 2.6 across the board in the OTS maps). You have to incrementally increase it to get a linear requested boost. See the attached pics and you'll see what I mean.

I think whether people see in gear timing flatlines or flatlines shifting into those gears that this would work. I'm not talking about knock retard on shifts.

Here is a log of the beginning of 5th gear where I used to always flatline (about negative 5 degrees) and now I don't. Timing is right where I currently have it set for this load / RPMs http://www.datazap.me/u/mfish123/no-...-or-5th?1-9-19

Below are the load targets and boost limit multiplier values and main timing I have currently. I'm slowly increasing to find my car's limits.

Hope this helps. The real person to thank is Carl Morris. He's helped me immensely in ATR and made me aware of this method.