Right, this little problem has reared its head a few days into S/C ownership.

On harder (brisk lets say) acceleration in lower gears my MY07 4.2 S/C makes a very strange noise. It almost sounds like its in the cabin, certainly behind the driver. Its like a metallic rattle, it could even be audio speaker crackle related its such a strange noise. Almost like a "white noise" noise. Ive tried with the stereo of and it made no difference, I have also tried turning the rear fans of just incase its something stuck in a duct touching a fan whilst under acceleration.

Its only apparent in lower gears where acceleration is greatest.

I havn't actually done much experimenting with it just wondering if anyone could give me some pointers.

I'm thinking it could be an exhaust baffle or some sort of heat shield? What do people think? 2005 E60 M5
2006 (MY07) L322 4.2 S/C
2024 i7 xDrive60
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2004 L322 4.4 Vogue, 2002 L322 4.4 HSE, 2006 (MY07) L322 S/C , 2001 P38 Vogue, 1999 P38 4.6 HSE.

Maybe the engine pinking?

Could be one of the cats is breaking down internally? Current Fleet:-
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47p2 wrote:

Maybe the engine pinking?

nicksaab wrote:

Could be one of the cats is breaking down internally?

Exhaust heat shield? Bish.

2005 110 TD5 CSW
2011 TDV8 Vogue SE (gone)

From your description , it sounds like the noise is only apparent when the supercharger is really doing its stuff .

But why you would here it behind you I don't know !!!

( btw , if you hear a noise like marbles rattling around in the nose of your supercharger it probobly needs a new coupler .
And they ALL definately need new oil .... these things are supposed to have an oil change , just like our "sealed for life" transmissions !!!
A snout rebuild kit with new bearings and oil is only around $100 ... )

I'd look at turning all hvac off so the flaps close , and sitting in the back whilst someone else drives to identify where it's coming from .

Cats can normally be heard with front windows down driving close to a wall .
Or tap them by hand or with a rubber mallet to listen for rattles .

My local dealer will replace cats for free up to 10 years old or 85,000 miles .

Mine went at 86

I dont think its supercharger related to be honest, mainly as it doesn't occur in higher gears. If it were S/C related it would be there in every gear at a certain RPM etc. I had to "make use" of the power plant this weekend a couple of times - dawdling tourists between Glencoe and Loch Lomand required some committed multi vehicle overtakes!

Its still there, intermittent to be honest, I might have just got used to it.

I'm sure its still an exhaust baffle or something like that.

This week's job is to price up a service now we are back from Scotland, I've a few places I'm going to get a quote from and go from there. 2005 E60 M5
2006 (MY07) L322 4.2 S/C
2024 i7 xDrive60
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2004 L322 4.4 Vogue, 2002 L322 4.4 HSE, 2006 (MY07) L322 S/C , 2001 P38 Vogue, 1999 P38 4.6 HSE.

theres a few heat shields under there, in and around the transfer box as well. get under there and tap them all to see if any are loose or catching on something. Its likely to be a heat shield i would think. I had one making a bit of a buzz on mine, couple of mins under it had found it and bent it back into shape.  There is nothing that can't be fixed with a hammer😜😜
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