[AD18]

Hi All,

I posted this question in the UK forum but things seem pretty quiet there now, so thought I'd try here.

Has anyone with a 335i experienced their turbo 'hissing / psss' sounds have stopped?
Where previously I could get sounds from building some boost and letting off, I can no longer get any no matter what. I'd like to investigate why this has happened as I feel there are some knock on effects, but not sure how or what to look into.

Symptoms:
- Turbo sounds have gone
- Car feels slower in the lower rpm ranges, as if I need more throttle to do simple overtakes on the motorway.
- At higher rpms car pulls strong, but this gives the feeling of a heavily turbocharged car where its slow at low rpm and then fast at higher. (Thought the car felt faster than this but maybe I'm just used to it now?)
- Lumpy engine running at idle

I thought either:
- Diverter valve (/BOV?) is passing / not sealing properly
- Small leaks from some hoses
- Perhaps starting to experience issues with the turbo itself.

Car is all stock and now on 100k miles, no error codes.

I don't have the equipment but I thought if there was a way of measuring turbo boost pressure then that might reveal something?

Any advice or avenues to explore will be helpful

Thanks

[TheGoodTheBadTheUgly]

Hello, might be something super simple as a boost leak because of loose components and on the extreme end, whicj is more unlikely, could be issues with the turbo itself.

You are right that measuring the built boost would be the best way to diagnose what is going on.

The N55 is equiped with a TMAP sensor (temperature-manifold absolute pressure) on the chargepipe before the intake manifold and by reading its output values compared to what is requested by the car's ECU, we can learn more about potential boost leaks. We can also look at wastegate duty cycles if we must go further.

I recommend getting a proper scanning and logging tool for this car. You can learn a lot from it, diagnose multiple things and prevent larger issues from happening.

Getting the MHD N55e monitor pack with a MHD OBDII device would be good.

You could also see if Torque App and a regular bluetooth adapter could work.

Meanwhile, have you checked to make sure that you have no obvious hardware issue? Is the chargepipe showing cracking (this is a well documented issue that has arised multiple times even on non tuned/stock cars)? Are all the pressure pipes still well connectes to each other as wrll as the intercooler?