[junlikesf30s]

Sup all,

My car is a 2016 435i Gran Coupe with 67k miles.

This is my first turbo BMW and I'm trying to figure out if it's normal to hear a low-pitched spool in low RPMs, 1500-2500rpm in 1st-2nd gear. This is also my first car with a twin scroll turbo.

I've tried searching here and on google. I've tried looking for "stock 335/435i pov drive" videos. Can't seem to find any info on this. I bumped into one video by random a few months ago and that 335i had the same low gear/rpm spooling sound, but I can't find it anymore, it's lost somewhere in my Youtube history lol.

Only hear it when starting from a stop; stop light, stop sign, parking spot, etc. It's not there if in park or neutral, and it goes away when building higher boost past 2500rpm. It's not there when in 3rd-8th gear. It's RPM based, not speed, so it's not the transmission. When i hear it and i let off the throttle or the car shifts, the sound follows the RPM. It's not obnoxiously loud, it's a low-pitched "weeeooooouu, shift, weeeoooouu". It almost sounds like radio/speaker interference, but coming from the engine bay. ASD is deactivated. No fault codes, no loss in power, no issues in drivability.

I'll try to record a video, but last time i tried with my old Note 10 Plus, it couldn't pick up the sound. I'll try again with my new phone.

I'm thinking:
1. it's normal and it's the low boost side of the twin scroll turbo?
2. it's not normal and turbo is starting to die?
3. it's not normal and I have a small boost/vacuum leak that isn't popping a code?

Any insight is greatly appreciated!

[thejeremyman9]

What intake are you running? you are probable just hearing the DV

[Timevampire]

I have the same car and it makes a bunch of sounds. I started hearing a lot more from the turbo when I made changes to the intake. If the sounds are new, might be worth checking the intake piping for tears or disconnects. I was surprised how long I was able to drive around with my intake partly disconnected from the inlet pipe before throwing a code.

This car also has electric wastegate and diverter valve and I assume some of the weird sounds are related to those.

[junlikesf30s]

Originally Posted by thejeremyman9

What intake are you running? you are probable just hearing the DV

Jeremy! You're all over this forum!! Lol. I was the guy throwing CELs when I did the K&N drop in+MPPK-style air box mod.

I'm running the CTS Turbo intake at the moment, but the whir/howl noise was present before i put on the intake. I thought it was possibly the acc belt tensioner/idler, so when i did my spark plugs, i did the belt, tensioner, and idler as well, but the sound is still there. Kind of hard to explain the sound, other than it sounds like a turbo spooling up, but its a lower muffled frequency "wooo" sound VS the high frequency vacuum "schhh" sound, kind of sounds like a belt that has too much tension; aka a serpentine belt or a supercharger.

i forgot to take a vid today and it's gona have to wait. Car is parked for the week while I wait for my Potenza RE71RSs to be delivered to my tire shop. One of my damned RFTs started separating from the sidewall from dry rot while i was omw back from the mall, but managed to limp home and will limp to the tire shop up the street when its time. Such is life.

edit: what's weird to me is that the tire is still holding air even with a fat ass hole in the side wall. I can literally see the thick ribbing of the RFT rubber. lol

[junlikesf30s]

Originally Posted by Timevampire

I have the same car and it makes a bunch of sounds. I started hearing a lot more from the turbo when I made changes to the intake. If the sounds are new, might be worth checking the intake piping for tears or disconnects. I was surprised how long I was able to drive around with my intake partly disconnected from the inlet pipe before throwing a code.

This car also has electric wastegate and diverter valve and I assume some of the weird sounds are related to those.

Any chance you could shoot a vid and post it on youtube for me?

I just need:
- Comfort mode, transmission in D, no S or M mode
- Normal driving, from a stop, light to medium throttle and acceleration to speed limit
- Windows closed, radio muted, HVAC fan on low or off; basically mute as many things as possible so i can hear the engine bay

I want to see if my car sounds like yours.

I would greatly appreciate it!!!

[Timevampire]

Originally Posted by junlikesf30s

Any chance you could shoot a vid and post it on youtube for me?

I just need:
- Comfort mode, transmission in D, no S or M mode
- Normal driving, from a stop, light to medium throttle and acceleration to speed limit
- Windows closed, radio muted, HVAC fan on low or off; basically mute as many things as possible so i can hear the engine bay

I want to see if my car sounds like yours.

I would greatly appreciate it!!!

I can but nothing on my intake side is stock anymore.

[Smooth_Operator]

I'm running the CTS Turbo intake too, it's super loud. From what I remember before installing it, I could hear some turbo noise before installing, mostly in parking garages and tunnels. Personally I think you're probably fine. Just pop the hood and make sure everything is connected properly and make sure it isn't throwing any codes.

[thejeremyman9]

I agree its probably just air sounds from the intake. The DV noises that sometimes sound like squeals or 'pshoooo' sounds when on light throttle accel/shifts is exactly what annoyed me when i temporarily ran the CTS intake. This is in addition/separate from the air 'intake' sounds from the turbo sucking air.

The only other thing that comes to mind is the valve cover squeal noise that can happen. You might want to google that one

[junlikesf30s]

Originally Posted by Timevampire

I can but nothing on my intake side is stock anymore.

ah all good lol. would still appreciate a short clip if you're up for it.

[junlikesf30s]

Originally Posted by Smooth_Operator

I'm running the CTS Turbo intake too, it's super loud. From what I remember before installing it, I could hear some turbo noise before installing, mostly in parking garages and tunnels. Personally I think you're probably fine. Just pop the hood and make sure everything is connected properly and make sure it isn't throwing any codes.

i've checked the boost pipe, charge pipe, intake pipe, everything seems solid. still planning to replace the plastic charge pipe though; i'm not tuned, but i want to do it as a preventative measure. no codes too.

i'm just being OCD/anal i guess lol. thanks for the ease of mind!

[junlikesf30s]

Originally Posted by thejeremyman9

I agree its probably just air sounds from the intake. The DV noises that sometimes sound like squeals or 'pshoooo' sounds when on light throttle accel/shifts is exactly what annoyed me when i temporarily ran the CTS intake. This is in addition/separate from the air 'intake' sounds from the turbo sucking air.

The only other thing that comes to mind is the valve cover squeal noise that can happen. You might want to google that one

yea i think i'm just being too critical/anal lol.

i've done the PCV test and cap test and they check out. no leak at the front main seal either. the engine looks relatively spotless aside from dust build up, def surprised me for a car with 65k miles once i started poking around the engine bay. It's as clean as my 05 S2000 i bought back in 09 with 23k miles.

[junlikesf30s]

can barely hear this "issue" now that i installed my axle-back. problem solved? lol

[junlikesf30s]

confirmed!!!!

it's the Diverter Valve or Electronic Waste Gate. stuck a mic down both sides of the lower engine bay and recorded, it's coming from the hot turbo side. in 1st and 2nd gear, the DV/EWG is stuck open from 1k-2.5k RPM. I'm assuming BMW did this so you aren't building boost/too much power in low gear low RPM city/traffic driving; would help with MPG, drivability, heat soak.

[thejeremyman9]

Originally Posted by junlikesf30s

confirmed!!!!

it's the Diverter Valve or Electronic Waste Gate. stuck a mic down both sides of the lower engine bay and recorded, it's coming from the hot turbo side. in 1st and 2nd gear, the DV/EWG is stuck open from 1k-2.5k RPM. I'm assuming BMW did this so you aren't building boost/too much power in low gear low RPM city/traffic driving; would help with MPG, drivability, heat soak.

You can datalog WGDC which basically tells you the position of the WG for an EWG and you can see how open it is