I don't know if this noise has been going on since I bought the car or what but I have 01' Audi A6 2.7T with 103K on it and it's making a weird noise like it's whining down when I let off the gas. I bought it with 92K and I was doing an oil change today and cleaned my K&N air filter with the charger kit. I also took out my air box and cut the bottom out of it cause I saw on another forum that someone had an S4 with the same engine and they said it added a few more hp and let the car breath a little better. Any chance that cutting out the bottom could be causing the noise when letting off the gas? Any help would really be appreciated.

 

Yes. You are now hearing normal intake noises that are usually muffled by the air box. BTW, the stock air box in stock form is supposed to be good for more HP than you will ever get the car to make AND it is all cold air instead of the hot air you are now sucking in.

Bob

 

Bob are you sure it's from cutting the airbox cause I only notice it when the turbo's are boosting which I belive is at or around 2800 rpms, anything under that I don't hear the sound. I was thinking it might be the blow off valves but I don't hear the sound when it shifts to the next gear, it's only if I'm accelerating over 2800 rpms and I let off the gas. It's sounds like when your shutting off your vacumm cleaner. Weird?

 

Chi:

Any time you open up the normally closed intake tract, you're going to hear new noises that are normally suppressed by the closed system, JUST LIKE BOB SAID. I hear similar ("chuffing", if you're into onomatopoeia) noises from the intake system of my 2005 Excursion with an AIRAID cold air intake, especially when letting off the throttle after moderate to hard acceleration, and more especially when it's cold. What you're hearing is the noise of the air being inhaled at HIGH speed into the compressor sides of the turbos, so you may want to get used to it, if you're going to stick with your modified intake.

Also, JUST LIKE BOB SAID, you are now drafting hot air from the engine bay into your formerly cooler intake tract - what works for some guys S4 will not necessarily work for an A6 just because they're both Audis. Do yourself a favor and get a new airbox or fix the one you cut.

How many miles did you put on your K&N before you cleaned and reoiled it? I usually don't do anything to my K&N-equipped vehicles until the filters have close to 100,000 miles.