Drives: 2006 BMW E90 330d M-Sport. Join Date: May 2014. Location: Midlands, UK. iTrader: ( 0) I had a similar noise on mine, was proportional to engine RPM. In my case it was the alternator, more specifically the alternator bearing. Replaced the alternator and the noise is gone now.
Same setup as me, should be 32psi all round (2.2 bar I believe) as per the sticker inside the driver's door. So my f30 has flashed up with low tyre pressure warning but highlighted all tyres on the screen. So I have a 320i xdrive saloon with the m sport pack 19s wheels run flat.I average slightly better mpg in my 330d (38-40mpg) compared to my pre LCI 164bhp E90 320d auto (36-38mpg) My E46 164bhp 320d SE auto was better than both though at around 40-42mpg but it did have narrow Michelin Efficientgrip tyres.
smn3.