[smokinu454]

Hey guys I have a 2016 535i. I just installed new plugs, new coils, VRSF charge pipe, VRSF catless downpipe, VRSF intercooler, XHP stage 3, and MHD stage 2+. The car seems to be running great but im having trouble understanding what the actual boost is doing vs desired in the logs. I know the stock n55 turbo struggles to keep up in the higher rpms but I have had 2 other F10 N55s with the same tune and mods that seemed to keep up a little closer. MHD is saying to look for a boost leak or an obstruction in the turbo inlet. The local indy shop that did the work says it looks fine, like a typical N55 so im not sure if im chasing my tail or not. I wanted to see what you guys thought. Here are 2 3rd gear pulls and a 4th gear pull.

https://datazap.me/u/smokinu454/n55-...og=0&data=4-19

https://datazap.me/u/smokinu454/n55-...og=0&data=4-19

https://datazap.me/u/smokinu454/mhd-...og=0&data=4-19

[DementedF10]

Im not going to say i know a whole lot on what these show but to me, and based off my own logs, It looks fairly normal. There a few over boost spikes Im not sure about when coming off the throttle but maybe that is just before the bov opens. For the measured boost vs target boost, looks as it should imo. I had a small boost leak from my factory BOV which was torn internally. I would see around 10-12lbs of boost and occasionally hit 13.4 a couple times and was very inconsistent on the graph. Since I replaced it, it looks more like yours does.

[smokinu454]

Originally Posted by DementedF10

Im not going to say i know a whole lot on what these show but to me, and based off my own logs, It looks fairly normal. There a few over boost spikes Im not sure about when coming off the throttle but maybe that is just before the bov opens. For the measured boost vs target boost, looks as it should imo. I had a small boost leak from my factory BOV which was torn internally. I would see around 10-12lbs of boost and occasionally hit 13.4 a couple times and was very inconsistent on the graph. Since I replaced it, it looks more like yours does.

Thank you for the reply! Im glad to hear that it looks fairly normal. What tune are you running?

[DementedF10]

I have MHD stage 2 93oct. No burbles etc. Might do an intercooler when I come across one reasonable enough and see what 2+ feels like if any difference.

[smokinu454]

Just want to bump this and see if anyone else has any thoughts on why desired boost is so much higher than actual? I have heard the turbo inlet pipe on the f10 is very restrictive, curious if not having enough intake airflow could cause this also?

[Unspec]

Yes, the turbo inlet can definitely cause underboosting by 1-2psi. The tune assumes minimal restrictions.

Your diverter valve could also be going bad or is just unable to hold the higher levels of boost.

[smokinu454]

Well installed a new higher flow turbo inlet pipe today and the smoke tested under pressure, no boost leaks. Still seeing boost about 2psi less than target.

[Unspec]

Sounds like a bad diverter then.