N55 stutters on boost

Sharas_v6

New Member
Oct 7, 2020
2
0
0
Hi,

I have this issues where the engine struggles and stutters on boost at midrange, anywhere from 3500-4000rpm, mid to high throttle, running MHD and their OTS "Stage 2+" map and I am running out of ideas - maybe someone has some insights before i throw in the towel.
I have already replaced the ignition coils to new Delphi units, 2nd set of plugs - had NKG 97506, switched back to OE Bosch gapped down to ~.025, fuel pressures seem ok, no codes from the ecu.

The car: 2011 135 with DCT trans, stock pwg turbo, running on 91 octane
The mods:
Injen intake, intercooler with charge pipes, catless downpipe
GFB metal diverter valve (no 2ndary spring)
*catch* - i have done some light headwork, only blended in the valve seats and cleaned up the ports, nothing crazy.

Logs - 2 short pulls, one 2nd gear, one 2nd to 3rd, you can see how choppy the rpm curve is:

I am not a fan of all these OTS tunes, but want to make sure I am not missing something simple before i go spending money on a real tune.
 

matt cangie

New Member
Aug 8, 2018
6
2
0
Ride
335iX
Have you checked your plug gaps? In you logs, your TPS never hits WOT. Are you sure you're flooring it?
 

machinehead

New Member
Dec 11, 2020
6
1
0
can you do a log where you hold the pedal at wide open throttle?
The throttle might be closing to limit the boost.
 

machinehead

New Member
Dec 11, 2020
6
1
0
You are overboosting and the throttle is closing to control the boost, same problem on my car. I don't have a fix yet.
 
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Jobe0074

Lurker
Dec 9, 2021
14
3
0
Melbourne
Ride
M135
Had similar issues with misfires at WOT -
Sure you have BUT, I’d triple check that the coil boots are totally engaged on the plugs
Check for any arcing etc
Potentially could also be a vacuum leak somewhere - maybe try a smoke test
Major PITA chasing these stutters / misfires etc
Wish you luck buddy