[NRudy]

Running a N54 335i.

On thing i notice that full throttle on gear changes (7k ish in DS mode auto box) the turbos seem to spool down on change.

I would have thought the turbos would stay spinning and pushing hard on change to keep the boost up? Does anyone else notice this?

Now i know if your revving hard and you let off they would spin down but if you keep your foot down should they stay pushing?

[Dann]

They will stay spooled up but your wastegates will open and drop the boost pressure.

The turbos shouldn't stop spinning though.

[borinous]

they shouldnt spool down as the exhaust gases flowing into them will not stop.

but +1 the wastegate will open to let out the excess boost sounds normal to me

[abeardo83]

You'll be hearing the wastegates opening. It's surprisingly loud, IMO. Would rather have that though, than some chavvy dump valve.

[NRudy]

Originally Posted by abeardo83

You'll be hearing the wastegates opening. It's surprisingly loud, IMO. Would rather have that though, than some chavvy dump valve.

So the whine noise is the wastegates opening on gear changes? And the hiss at around 3-2k as revs come down is them closing?

Might seem like something simple but given its an N54 every noise could mean death. My turbos are only 8 months old.

[abeardo83]

Not from what I understand. The wastegates open as the revs increase. This is because the turbos only need a certain amount of boost pressure.

On deceleration, all I can think of is the blowoff valves kicking in. Thankfully they dump in to the air intake, rather than directly outside.

Take a look at this - excellent read.

http://www.e90post.com/forums/showthread.php?t=38856

[AWSAWS]

Assuming you're steptronic (Automatic) OP and not manual. Makes a big difference on the boost during shifts.

[windymissile]

Turbo's are at their best at about 3k. Is it dropping below this?

WM