I pulled up a search and only found 1 instance in an S4 that had a problem that was referred to as "wheezing" for approximately 20 seconds. What I am noticing is when I start the car, it fires up abruptly and runs normal. As the car is warming up it begins to "whistle". From my knowledge, I would think the turbo is spooling up to get oil running through it, as well as warm it up. I also hear the relief of pressure from the turbo after this period. Im assuming its either A. the Turbo or B. The Rad fan, but I highly doubt that because there always seems to be an increase is rpm of the noise and then it will whistle for a short time and stop. I dont have an intake so I dont see it being the intake whistle. I dont know of any intakes that whistle on this motor. Do they?

I have a strong feeling its just the turbo coming to operating temp, but has anyone else expereience this as well?

 

in a cold weather maybe first 10min, my dv whisles (i think it comes from the dv) when I shift. then backs to normal.

 

Happens to me too. Strangely, it started happening right after I installed my amp for my sub. Sometimes it does it, soemtimes it doesnt. Its ONLY on a cold startup too. I cant figure it out, but everything seems fine turbo/boost-wise.

 

It does from what I remember only happen when its cold out, but the last time it happened a friend brought it up asking what the sound was. I had driven the car to a local walmart to get a Qt. of oil, it sat for roughly 10-20 minutes and upon restart is when he noticed it. the motor should have still been warm. Im concerned if thats a sign of some sort of turbo inlet damage or shaft damage or if its just normal. You would think if the ambient temp was cool or hot it shouldnt matter. If thats how the turbo comes to operating temp, it should logically do it everytime. Wouldnt you think?

 

mine does the same. its the secondary air pump. on a cold day if your engine is cold then the secondary air pump recirculates part of the hot exaust into the engine to help bring it up to temp faster. so the whistling is the pump turning on for how ever many seconds at a time. mine usually cyles twice, three time if its really cold outside. this is what i was told by my friend, he works at the audi dealership as a certified tech.

 

that would definately make sense as a secondary way to get air into the motor. Im just surprise noone else knew/knows about it. Do you know the exact location? It really does resemble a fuel pump hum come to think of it.