Stock turbo question

**RVT** · 01-27-2009 08:16 PM

Question for those of you in the know....

The A4 is my 4th turbo vehicle, and the first one I have ever heard the turbo "spool down" after shutting off the engine. Pretty sure it is the turbo from the sounds pitch and location (doesnt do it all the time). This cant be normal for this car can it?
My three priors were all Mitsubishi turbos, and they were dead silent on spooling down.

I'm wondering if the bearing are going away...

Thoughts?

thanks
Vince

**Zebman** · 01-27-2009 08:24 PM

It's not the turbo. It's the AC compressor. If you turn on the AC and turn it off, you can hear the sound at different times.

**RVT** · 01-27-2009 08:49 PM

Originally Posted by Zebman

It's not the turbo. It's the AC compressor. If you turn on the AC and turn it off, you can hear the sound at different times.

That would be awesome, I'll go play with the system a bit to see if I can replicate it regularly. I know AC can run on occasion just a part of the environmental controls, but its been in the low 30s here for the last two weeks! Still... makes more sense (and less worry)that the turbo.

thanks
(Wish it would warm up so I can go get under this hood for a day....brrrrrr)

**Heratik** · 01-27-2009 10:20 PM

This is my first turbo vehicle and I've also heard the sound that you describe. I just thought it was normal.

**agorich** · 01-29-2009 08:45 PM

yeah, my first turbo as well. and it seems normal. i always thought its just the fan/belt slowing down. no matter if its the ac/heat/fan or what have you. it always comes on unless i turn it off completely

**Phantom08** · 01-30-2009 09:17 AM

That is the sound of the turbo. Compared to the old 1.8T the newer 2.0T run for a few seconds after the car is turned off.

**b6onboost** · 01-30-2009 09:30 AM

^ no it's not. it is the AC compressor. 1.8Ts do it as well. Sounds like a space ship powering down. Turn you HVAC to 'off' and you won't hear it.

**Latin Audi** · 01-30-2009 09:33 AM

Originally Posted by b6onboost

Sounds like a space ship powering down.

Lol that's exactly how it sounds. I've always wondered what it was too, but I never thought it was the turbo.

**cmdsm** · 01-30-2009 11:27 AM

I always figured it was the fans slowing down, but if the sound isn't present when the ac is off then there you go.

**Phantom08** · 01-30-2009 12:01 PM

I always assumed it was the turbo. My 1.8T caused a buildup of sludge in the engine and ended up costing me a fortune to fix. The dealership said they fixed that problem by allowing the turbo to run longer and that was what the sound was. But if it's the AC.....I guess I'll have to keep fooling myself and my friends!

**Insane_Audi** · 01-30-2009 12:05 PM

Originally Posted by Phantom08

I always assumed it was the turbo. My 1.8T caused a buildup of sludge in the engine and ended up costing me a fortune to fix. The dealership said they fixed that problem by allowing the turbo to run longer and that was what the sound was. But if it's the AC.....I guess I'll have to keep fooling myself and my friends!

That is why there are turbo timers, to let your turbo run a little so if your in a hurry the turbo can cool down after the engine being shut off. It saves a lot of miles on your turbo.

**RVT** · 01-30-2009 12:13 PM

Originally Posted by Latin Audi

Lol that's exactly how it sounds. I've always wondered what it was too, but I never thought it was the turbo.

Yeah, my only fear was that it was a BAD turbo, not that one would normally sound like that. The car is too new to me, so I haven't got a boost gauge installed yet either.... Don't have a clue if I am even getting full boost cause the powerband is so flat.

My stockl '91 Galant VR4 (also an AWD car) would slam you back in the seat when the unit spooled up. My A4 isn't nearly as quick, which for a car 14 years newer is kinda disappointing. Still, I think the A4 has an extra 400lbs or so to push around over the Galant too.

Originally Posted by Insane_Audi

That is why there are turbo timers, to let your turbo run a little so if your in a hurry the turbo can cool down after the engine being shut off. It saves a lot of miles on your turbo.

These are a "must have" if you choose to run standard oils instead of Synth (IMO).

V

**wayneB7** · 01-30-2009 04:18 PM

Hmmmm .... this is indeed interesting because I park in a garage nest to a wall and I have excellent hearing -- my car makes zero sounds when I switch it off. Other than seeing the turbo I hardly know it is there at all. I am not running my AC at this time either (car is on Econ), so my car's behaviour supports the theory that it is the AC compressor. Either way it is not the turbo.