[Tyc0]

Hey guys, I'm working with my tuner to get things dialed in with my new turbos, and I notice that when I go near redline the boost looks weird after I let off. It feels as if my BOV lets out half and then closes again and then the rest. But this only happens near redline, any other time the BOV lets it all out at once. Tuner said he's never seen anything like this. Any ideas ?
Here is log: https://datazap.me/u/tyc0/revision-5?log=0&data=3-6-22

[Bimmer_Bro]

Originally Posted by Tyc0

Hey guys, I'm working with my tuner to get things dialed in with my new turbos, and I notice that when I go near redline the boost looks weird after I let off. It feels as if my BOV lets out half and then closes again and then the rest. But this only happens near redline, any other time the BOV lets it all out at once. Tuner said he's never seen anything like this. Any ideas ?
Here is log: https://datazap.me/u/tyc0/revision-5?log=0&data=3-6-22

Which bov or dv setup are you using?

[335igasm]

^ What BOV/diverter valves?

[Tyc0]

Originally Posted by Bimmer_Bro

Which bov or dv setup are you using?

Turbo smart Race port gen 4, never given me issues

[Tyc0]

Originally Posted by 335igasm

^ What BOV/diverter valves?

Turbo smart race port gen 4

[studio54]

Weird that the boost target get down when you let off and get up again without touching the pedal.

[335igasm]

Originally Posted by Tyc0

Turbo smart race port gen 4

Have you tried adjusting the spring pressure?

[Tyc0]

Originally Posted by 335igasm

Have you tried adjusting the spring pressure?

Spring pressure has nothing to do with the fact that the boost target in the computer goes back up, so no I haven't.

[studio54]

Originally Posted by Tyc0

Spring pressure has nothing to do with the fact that the boost target in the computer goes back up, so no I haven't.

That's what i thought about boost target but...

Completely hypothetic stuff here if it's not software related :

maybe the accel pedal position controls the throttle position, and then the throttle position controls the boost target

if your BOV/DV fail or something, maybe the boost remaining in the chargepipe forces the throttle body plate to open resulting in this weird boost target thing ?

i say that, because, your boost isn't released quickly as you can see on your log, it's slowly dropping to normal negative psi reading... during the fall down, it's still at 10-12 PSI when you released the pedal....

[Tyc0]

Originally Posted by studio54

That's what i thought about boost target but...

Completely hypothetic stuff here if it's not software related :

maybe the accel pedal position controls the throttle position, and then the throttle position controls the boost target

if your BOV/DV fail or something, maybe the boost remaining in the chargepipe forces the throttle body plate to open resulting in this weird boost target thing ?

i say that, because, your boost isn't released quickly as you can see on your log, it's slowly dropping to normal negative psi reading... during the fall down, it's still at 10-12 PSI when you released the pedal....

You are correct, but I can only make this happen past 6k rpm, even with the same amount of boost at 4-5k it lets it all out at once. Which is why I don't think this has anything to do with BOV

[Tyc0]

Tuner said he adjusted some sort of throttle tables in new map (way beyond me so don't ask for explanation) but this didn't seem to do anything. It seems I have a fairly rare issue here...gotta love it

[Saif2018]

Originally Posted by Tyc0

Tuner said he adjusted some sort of throttle tables in new map (way beyond me so don't ask for explanation) but this didn't seem to do anything. It seems I have a fairly rare issue here...gotta love it

Strange that boost takes so long to drop off throttle, May be boost solenoids playing up,

Throttle and accelerator positions look fine.

Just had a look at a previous logs, you don't seem to have this issue upto 6.5k at least on revision 3.

[Tyc0]

Originally Posted by Saif2018

Strange that boost takes so long to drop off throttle, May be boost solenoids playing up,

Throttle and accelerator positions look fine.

Just had a look at a previous logs, you don't seem to have this issue upto 6.5k at least on revision 3.

Thanks for input, my boost solenoids are probably only 2k miles old. I'll mention what you said to my tuner.

[Saif2018]

Originally Posted by Tyc0

Thanks for input, my boost solenoids are probably only 2k miles old. I'll mention what you said to my tuner.

That pretty much rules out the solenoids then,

No worries. Might be worth emailing MHD and mentioning the issue to them, asking for Datalog analysis and possible cause.

Mhd.tuning@gmail.com

[studio54]

Originally Posted by Tyc0

Tuner said he adjusted some sort of throttle tables in new map (way beyond me so don't ask for explanation) but this didn't seem to do anything. It seems I have a fairly rare issue here...gotta love it

Ok that's weird so, can't you try/flash an OTS map (any MHD stage or something) to rule out if it's hardware or software related ?

[CarAbuser]

Log the torque limiter channel, some torque interventions from the trans can request throttle to open.

[Tyc0]

Originally Posted by CarAbuser

Log the torque limiter channel, some torque interventions from the trans can request throttle to open.

That's the weird BMW answer I was looking for, I will try that.

[Tyc0]

So I emailed MHD and they told me this, anyone know about this?

Hi,

we can not help with custom tuning but the 1M for example has a "anti lag shift" already included, this means if you go full throttle, release the throttle and press the clutch in for shifting then the DME tries to hold the boost up so the lag will be reduced. If you just release the throttle without pressing the clutch then the boost will be released.

[Saif2018]

Originally Posted by Tyc0

So I emailed MHD and they told me this, anyone know about this?

Hi,

we can not help with custom tuning but the 1M for example has a "anti lag shift" already included, this means if you go full throttle, release the throttle and press the clutch in for shifting then the DME tries to hold the boost up so the lag will be reduced. If you just release the throttle without pressing the clutch then the boost will be released.

You have a 1M?

1M has overboost function, I recall hearing about it even in reviews, so if it has anti lag, then that would make sense.

[Tyc0]

Originally Posted by Saif2018

You have a 1M?

1M has overboost function, I recall hearing about it even in reviews, so if it has anti lag, then that would make sense.

No I wish! Just a e92

[Saif2018]

Originally Posted by Tyc0

No I wish! Just a e92

Ok, I think MHD suggesting it might be deliberately mapped in,

Looks like it's map related, since revision 3 boost falls off pretty much straight away, when your off throttle,

Revision 4 onwards the boost drops gradually, when you go off throttle.

[Tyc0]

Originally Posted by Saif2018

Ok, I think MHD suggesting it might be deliberately mapped in,

Looks like it's map related, since revision 3 boost falls off pretty much straight away, when your off throttle,

Revision 4 onwards the boost drops gradually, when you go off throttle.

Does MHD launch control add this feature? That's the only thing I can think of that I changed.