N54 surging - slight overboost followed by throttle closure

[SmoothOperator]

Hi guys,

i have quite stock E90 335i, new 12 injectors, coils, spark plugs, lpfp, high flow cats, bigger IC. I run MHD OTS stage 2+ on 98ron. The cars runs ok, pushing around 18psi. But it´s kinda jerky going moderate to full throttle, especially in lower gears. What i can tell, from the logs, there´s slight overboost followed by throttle closure which translates to that surging feeling. I tried to open a little the wasgates by turning in the contoling rods by 2 turns and i am not sure if that helped or not. More likely didn´t, feels little different but it is still there. Can please someone chime in? Why isn ´t that solved by wastgates and dme is closing the throttle? Thanks in advance

 

[SmoothOperator]

log N54 surging

 

[SmoothOperator]

What i have also noticed, that before the slight overboost the WGDC goes from almost 95% dipping significantly low to 30-40ish, then the overboost happens which is corrected right away with throttle closing. Should I open the wastegates further or it isn´t that important? Does dme evaluate some initial starting point by opening and closing the wastgates on every startup and than commands the WG solenoids accordingly by the actual setup of the flaps?

 

[SmoothOperator]

And why it isn´t happening in higher gears ie 4,5,6? Also, it seems more prominent on partial throttles and/or in the beggining of pulls

 

[SmoothOperator]

I´ll do few proper 3rd gear pulls tomorrow, these logs i have are rather thrash i guess

 

[ShocknAwe]

Is it traction control? Appear to be venting pressure and dropping timing simultaneously.

Your base vs actual looks ok but load is quite close to request before the drop, if not wheel slip intervention I'd look at your wgdc and see if reducing a bit via one of the tables makes sense to you.

I'd be wary of manually adjusting the wastegate actuators if still fine tuning the flash. All you'll likely accomplish is making them slow to respond.

 

[SmoothOperator]

Is it traction control? Appear to be venting pressure and dropping timing simultaneously.

Your base vs actual looks ok but load is quite close to request before the drop, if not wheel slip intervention I'd look at your wgdc and see if reducing a bit via one of the tables makes sense to you.

I'd be wary of manually adjusting the wastegate actuators if still fine tuning the flash. All you'll likely accomplish is making them slow to respond.

Hello ShocknAwe. First of all, really appreciate your input, thank you!! And no i always turn off TC before logging..

That's perhaps correct. I think it is tune related. I made proper pull, which went ok (see attached), no throttle intervention. But seems to me, that the initial build in boost could be maybe quicker and also WGDC towards the end, rises alot and still the boost doesn't following the Target, tapering off instead.. that to me perhaps indicates, that wastegate flaps are opened too much mechanically. I' d tighten them back, it was initialy set about right i think, according to BMW TIS - closed at - 0,20bar, but still able to be rotated. And then somehow adjust the mapping of wastegates so WGDC don't drop this sharp, to mellow down the spike and not get overboost.?
But I am no tuner, I am using OTS. Could you advise me, where can I adjust WG tables or mapping? I have also JB4, currentlyuninstalled, I prefer logging better in mhd and on jb4 it would always put me in map 4, perhaps due to overboosts. That's why I first thought, it is rather hardware related.

3rd gear pull no throttle closure

 

[SmoothOperator]

Here is the other 3rd gear pull which had throttle intervention. This one was prior to the one posted above.

3rd gear pull from higher revs with throttle intervention

 

[ShocknAwe]

Ah it's OTS. Yes throttle closures are common on OTS maps.

 

[SmoothOperator]

Why is that? So they are more on the safe side? Any thoughts why I had similar problems with JB4? Can you suggest solution? Perhaps i can modify the OTS map slightly and flash it as a custom tune.?

 

[ShocknAwe]

Try a different version of the OTS flash. I can't remember but there are some that run farther from the ragged edge.