[zack9r]

Me, and with other n54 owners, have or had the dreaded wastegate rattle

While searching on the internet how to get rid of this, i came across a video that said to take out the vacuum canister(s) and rev the engine to see if the rattle is still there. And to my surprise, it was gone.

But i dont just want to run around with a car that has something undone. Can someone tell me what the vacuum canisters do and if its a bad thing to have then undone or deleted? Many thanks, criticism is not needed

Edit: or just completely skip the canister in general and run a straight line, bypassing the canister in general.

[fozzydj]

I did the same, I was getting a 30FF, waste gate related and removed the vacuum canisters and it improved.

As far as Im aware there more for higher altitude locations, they hold like a reserve of vacuum.

[Paliator]

I am located at 800 feet and I deleted my vacuum canisters and have no problem

[zack9r]

Originally Posted by fozzydj

I did the same, I was getting a 30FF, waste gate related and removed the vacuum canisters and it improved.

As far as Im aware there more for higher altitude locations, they hold like a reserve of vacuum.

I dont have the code, but for me its more about the rattle. I hate driving a semi prestigious car and it sounding like my exhaust is falling off

[turbohugh]

Did you confirm the canisters aren't leaking ?

[zack9r]

Originally Posted by turbohugh

Did you confirm the canisters aren't leaking ?

They are in fact, not leaking.

They are pressurized (able to tell by the pressure thats released when i disconnect the hose)

Im not getting s hose, i just simply want the rattle to go away, which 1/2 of the wastegate actuators isnt rattling (im pretty sure)

[nissubaru]

Some people argue that BMW installed them for a reason, which I want to believe, but I have had 0 issues due to removing the vacuum canisters. My understanding is they were added to assist with boost/low vacuum on startup or something like that. I think they just over-engineered it.

[zack9r]

Originally Posted by nissubaru

Some people argue that BMW installed them for a reason, which I want to believe, but I have had 0 issues due to removing the vacuum canisters. My understanding is they were added to assist with boost/low vacuum on startup or something like that. I think they just over-engineered it.

What exactly does the pressure do? Activate the wastegate and disengage it? Stuff like that?

[Sgop335]

O yea stuff like that

[turbohugh]

Might wanna retest them. Just because they holding 'some' vacuum doesn't mean they're holding to spec.

https://www.n54tech.com/forums/showthread.php?t=37438

[dpaul]

Originally Posted by zack9r

What exactly does the pressure do? Activate the wastegate and disengage it? Stuff like that?

FWIW, in this case vacuum is produced by a mechanical pump driven by the engine.

In normally aspirated engines, manifold pressure is always below atmospheric pressure, providing a reliable source of vacuum. But manifold pressure is sometimes positive (i.e. above atmospheric) in turbocharged engines so is not reliable.

There are two main functions of the vacuum in the N54. The first is to power the brake booster and the second is to operate the turbo wastegates. The wastegate is connected to a diaphram that is moved by the differential pressure between the atmosphere (nominally 14.7 psi) at one surface and whatever pressure is applied to the other surface. If the DME decides the wastegate needs to be closed to generate boost, it electrically operates the boost solenoids which are just valves between the vacuum source and the wastegate diaphram.

A reasonable guess is that vacuum cannisters are present to provide a buffer so that vacuum levels don't vary too much when loads are suddenly applied. Similar perhaps to including storage tanks on air compressors.

As for the observation that removing the cannisters improved the rattle, it seems likely that there was a leak, if not from the cannisters themselves, then from some of the vacuum lines to and/or from them, which were probably replaced or at least shortened when the cannisters were removed. I suppose some more subtle explanation is possible tho.

[zack9r]

Originally Posted by dpaul

FWIW, in this case vacuum is produced by a mechanical pump driven by the engine.

In normally aspirated engines, manifold pressure is always below atmospheric pressure, providing a reliable source of vacuum. But manifold pressure is sometimes positive (i.e. above atmospheric) in turbocharged engines so is not reliable.

There are two main functions of the vacuum in the N54. The first is to power the brake booster and the second is to operate the turbo wastegates. The wastegate is connected to a diaphram that is moved by the differential pressure between the atmosphere (nominally 14.7 psi) at one surface and whatever pressure is applied to the other surface. If the DME decides the wastegate needs to be closed to generate boost, it electrically operates the boost solenoids which are just valves between the vacuum source and the wastegate diaphram.

A reasonable guess is that vacuum cannisters are present to provide a buffer so that vacuum levels don't vary too much when loads are suddenly applied. Similar perhaps to including storage tanks on air compressors.

As for the observation that removing the cannisters improved the rattle, it seems likely that there was a leak, if not from the cannisters themselves, then from some of the vacuum lines to and/or from them, which were probably replaced or at least shortened when the cannisters were removed. I suppose some more subtle explanation is possible tho.

It went away after i disconnected the hose to the canister.

Abyways. Do you still think that if i got new hoses/disconnected and took out the canisters it could fix the rattle fix? I live in michigan and there is absolutely no elevation change for the canisters to be of any use

[turbohugh]

Originally Posted by zack9r

It went away after i disconnected the hose to the canister.

Abyways. Do you still think that if i got new hoses/disconnected and took out the canisters it could fix the rattle fix? I live in michigan and there is absolutely no elevation change for the canisters to be of any use

Maybe you should start by replacing all of your vacuum lines.
This car uses vacuum to keep the wastegates closed. The cans are vacuum accumulators and are used when you're in boots and haven't reached target boost level. Vacuum leaks are cumulative so one small leak here and another there ( like degraded or split lines ) could present intermittent symptoms. But the link i share explains that .

[dpaul]

Originally Posted by zack9r

It went away after i disconnected the hose to the canister.

Abyways. Do you still think that if i got new hoses/disconnected and took out the canisters it could fix the rattle fix? I live in michigan and there is absolutely no elevation change for the canisters to be of any use

Maybe I'm missing something. When you say the rattle went away after you "disconnected the hose to the cannister", do you mean you simply disconnected the hose then listened for rattle? Not completed the circuit by bypassing the cannister so that the boost solenoids were connected to the vacuum source?

[zack9r]

Originally Posted by dpaul

Maybe I'm missing something. When you say the rattle went away after you "disconnected the hose to the cannister", do you mean you simply disconnected the hose then listened for rattle? Not completed the circuit by bypassing the cannister so that the boost solenoids were connected to the vacuum source?

Im saying, that there was no vacuum source at all since there was no vacuum going to the wastegate.

[studio54]

I may have not understood correctly the question ?

You unplugged canisters hoses to check if rattle keep going or disapear, just to diagnose. I can help also help to know which is rattling, front or rear, but most likely unplugging after the boost solenoids with some caps to plug.

If rattle gone when unplugged, it's because wastegates are 100% open when no vacuum, but the problem it also mean no boost at all if you drive it, you can try.

Deleting canisters and bypassing them will not delete rattle.