Slight vibration at 4000rpm...

[JT-KGY]

I had this for a long time now....
Everytime when all windows and sunroof are closed.. and
the tech swings by 4000rpm... the engine tone would change
near 4000... and there's a little resonance-like vibration that you
can hear in the cabin (mainly cause a little rattling from my hand
brake)...
I do not know if this is normal or not.. since I do have the following mods...
ECIS intake, AA Gen3 and ERT UD Pulley on my 97 3.2L coupe.
Been having this for a while.. I can only hear it with all windows
closed (highways).. it is kinda annoy...
Does anyone that have the similar mods having the similar
problem?

Thanks,

[BAADDOG]

Originally posted by JT-KGY
I had this for a long time now....
Everytime when all windows and sunroof are closed.. and
the tech swings by 4000rpm... the engine tone would change
near 4000... and there's a little resonance-like vibration that you
can hear in the cabin (mainly cause a little rattling from my hand
brake)...
I do not know if this is normal or not.. since I do have the following mods...
ECIS intake, AA Gen3 and ERT UD Pulley on my 97 3.2L coupe.
Been having this for a while.. I can only hear it with all windows
closed (highways).. it is kinda annoy...
Does anyone that have the similar mods having the similar
problem?

Thanks,

Is the vibration in all gears and speeds at 4,000 rpm?

Is the sound about driver's right side of the tranny in the cabin?

[Guillermo]

I have a similar vibration a little higher than 4000...dealer tried to blame it on my shift knob... :

[JT-KGY]

Ya.. around 4000... and when it happens.. you can really hear
the engine's tone change..
I called a BMW shop.. they told me it's VANOS switching...
but i really think it might be the UD pulley?... Or maybe it's my
intake??
Just wondering those out there with similar mod have this...

[BMLRacer]

The vanos is a valid response. It's not the pulley, don't be so skitish blaiming it on the few mods you have. But, you should have done a flywheel, not a pulley. That way you'd still have a harmonic dampener on the front of the engine.

[FaRTaLOTTT]

Switch it all back and bring it to the dealer!!!! Just a suggestion...

[Rel44 M3]

On my 99, when the tach swings by 4000rpm, I can definitely hear an additional resonance in my exhaust note, which I base on the VANOS. Don't get any vibration in the cabin though.

[Bernanke]

This is the Notorious "Vanos Dip" for some reason at this rpm range the Vanos system has a mechanical dip for some reason, If you read about it in European car magazine you will understand more about it. Basically the more power you have the bigger the dip will be unless you use Redline oils (this helped alot). Use redline engine oil, Transmission oil, and differential fluid and you will gain HP and you will gain 12 lbs torque and 9HP at these "notorious vanos dip" so you will no longer have a dip (read october issue of European car under 95 M3 project). Dont worry this is fairly normal. There are ways to correct it so no biggie. hope that helps!

[monterey]

This is strange. When my tach hits 4K everything reaches equilibrium and the car is silky smooth and dead quiet traveling 90mph.

[BAADDOG]

Originally posted by BAADDOG


Is the vibration in all gears and speeds at 4,000 rpm?

Is the sound about driver's right side of the tranny in the cabin?

JT,

You did not answer the two questions so I will venture what may be the problem.

Your crank shaft may be out of balance and the harmonic balancer may be marginally effective.

The key finding is to determin if the harmonic sound occurs only under load?

In all gears and in at all speeds?

Good luck