RS4 engine bay noise

[MCPCJC]

Hi All
Hope to pick your brains on my B7 RS4, the car went to MRC late last year for the full carbon clean,servic,Hi flow filter and stage two map, just to get her running like she should.
All work done and car now performs well, except she now has an annoying plastcy noise coming from the engine bay. The car has been back to MRC and they gave it a good look over but couldn’t find anything. The noise only happens when driving and is most noticeable at approx 1800rpm in 6th gear, but also in other gears at approx 4000rpm, it seems to get quicker as the revs increase and sounds plastcy rather than metallic. It seems to be coming from the engine bay, I have checked all the areas that where worked on and all looks good. The secondary air injection was disconnected and mapped out and air intake flaps removed as per MRC recommendation.
Any help would great as its driving me nuts.
Many thanks.

[stevieturbo]

Wind noise or some undertrays or something not refitted correctly ?

You dont mention whether the alleged noise follows engine speed, road speed, other, etc etc

[MCPCJC]

Hi
The noise isn’t affected by wind or undertray, it seems to be linked with RPM, i imagine it sounds like a fan blade catching on its casing and gets faster as RPM increase. Also wondered if it could be the power air flap in the air box?
It only happens when under acceleration, if you are at a steady speed there is no noise.

[GreenV8S]

Does it sound as if something in the engine bay may be resonating under particular conditions?

I imagine that would be extremely tricky to pin down and might involve a lot of trial and error - just pulling on things until you find something that has some flex which produces a similar frequency when you tap it, try wedging something into any gap you can see to find out whether it makes any difference - that type of thing. You could easily get resonance from loose baffles inside the exhaust which need divine inspiration to track down.

[MCPCJC]

Thanks will be giving it another look at over the weekend. Any ideas if the power flap could cause this type of noise as from inside that’s where it sound like it’s coming from.

[Composite Guru]

If it sounds like a plastic sound and you have had work done on the air filter system maybe its worth checking around that area?

Does it have a filter box? Check inside it for anything loose?

[MCPCJC]

Hi
Had a look in and around air box today, found the power flap was a bit sticky so sorted that out went for a drive and the noise was a tiny bit better but still there🤨
The search continues.