Possible DV Leak? Not meeting Load/Boost/MAF Targets

byebyeVTEC

New Member
Jun 14, 2023
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Hello All!

Fairly new to the BMW / MHD world but have quite a lot of experience tuning other platforms using the COBB AP.

I recently got an MHD for my 2012 135i (DCT) and have been experimenting with the OTS tunes while I figure out self-tuning (amazing to find public XDF's for TunerPro, love this community!). The car has 125,500 kms on it and is essentially FBO (VRSF catted DP, M-sport muffler, charge pipe, ETS 7" intercooler).

Since the car is new to me I wanted to start with milder tunes and see how she does. So far I am loving the MHD but while looking @ logs it's clear I am not reaching boost or load targets. I'm running the MHD V1.84 maps for N55e, started with Stage1 93 and now on Stage2 91. My WGDC isn't too high (unless the WG is fully open past 60% and anymore has not effect), AFR are good (seems a bit lean but I guess that's good), just a touch of knock I'm not too worried about..... Seems like it's running well aside from the difference between targets and actual. Would love the opinion of someone who has seen more N55 logs than I do.

I remember back in the day tuning MazdaSpeeds it was common to have diverter valve leakage causing boost recirculation and lowering loads.... Is that common on these N55s as well? Or is it normal for there to be an offset between Load Req and Load Actual on these logs? The car is also making sub 300whp according to V-Dyno w/ smoothing @ 3 and Dynojet corrections (seems low).

Here's a 3rd gear pull from earlier today where you can see the issue. It is not the warmest today but I don't see signs of wheelspin and I had DCT fully off.

 

wheela

Lieutenant
Jun 4, 2021
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Twin Cities, MN
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2015 e84 X1 35i Msport
Welcome, glad to see another n55e!

Your observation about the delta between boost request and actual, and load request and actual seems to be the tuning approach of these OTS maps; that's what I've seen in my own logs, and others who've posted. I'm not a fan of that chasm personally...

Your wgdc% doesn't look very high, your boost is falling off pretty hard up top. Also your stft drops pretty negative up top, so you may have a small boost leak somewhere. The leaky DV's are a thing on this platform, but it's hard to tell if there is a problem given such a wide gap between target and actual. A leaky DV may not impact your trims though if it's just leaking back to upstream of the compressor.

I tried the 1.84 maps, but seemed to run lean on them, so went back to 1.60. Have you tried 2+? I never ran 2, but did 1+ and 2+. 2+ has higher load and boost request than 1+, but I get about the same load actual, boost actual, and wgdc% on both maps (catless DP on both tunes). Actually got my fasted 0-60 on 1+... Not sure if your lower boost is due to stage 2 vs. 2+, a leak somewhere, or combination of the two.
 
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byebyeVTEC

New Member
Jun 14, 2023
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Hi,

Thanks for the response! I am quite surprised to see so little N55e love on this forum..... what gives?

I tried out the V1.60 maps and it's a bit better but does seem to mimic the load gap strategy. With V1.60 boost is stronger but peakier so I guess that is why they were saying V1.84 was an improvement. My logs from last night are not the cleanest but I can still see a trend of boost rushing up to target then quickly drop down then trying to rush back up. I have limited data points to base this on but seems that V1.84 maintains a lower but smoother boost curve. With V.184 I never saw boost hit targes but with V1.60 it was definitely hitting the target before coming back down.

DV leaking would not affect trims. But that is an interesting catch on the file. Looking @ my V1.60 log I am running richer than V1.84 with much lower STFT.... There is also some residual timing correction happening in the V1.84 log though and that could potentially affect lamda?

I will give the 2+ maps a shot when I'm back from vacation. Could be that my car just flows well enough that the turbo can't push enough air to keep boost high with the conservative WGDC limits..... May be time to start building some of my own tunes.

 
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