I have a 1999 Audi A4, 1.8t with 160,000 miles on it.

For the past couple months, I have had a pretty nasty exhaust leak. Insane loss of power and even worse fuel economy. I recently got it taken in and fixed, seeing as the flex pipe under the shifter was rotted.

I get it back, noticing the insanely quiet purr of the exhaust, no irregular sounds, fluids in good condition and topped off.

Half way home, I realize I don't hear the turbo spooling at all. I had forgotten how quiet my car was and dismissed the notion.

Now I am on day two.. with my radio down and my head hanging out the window hoping for some sign of audible life.

The only things I have read to due with problems on the K03 not spooling have related in MAF and fuel injector issues. Mine are fine, and these people usually complain of a slight whine. Also, leaking lines to the turbo, which mine has been tested with no leaks.
Let me reiterate when I say it isn't spooling or cycling ''blow off'' when shifting: No sounds period. No whine, no bone shatteringly terrible course whirl of a breaking turbo. Nothing.

Could this possibly be an issue with the bypass valve or an issue within the manifold?

Also, my car doesn't feel like it has any loss of power without the spooling of the turbo, and it actually seems to be performing better than before the flex pipe even wore out.

(I must point out that the front of the bumper, mainly the driver side, was coated in frozen snow. I noticed it was clogging the air intake, which I assumed would be my issue (Sometimes it can be the most common thing you overlook that is the problem). No dice, problem remains.)

Is there any reason my mechanic could have manipulated or somehow disengaged the turbo while doing the exhaust work? That doesn't feel like common practice to me, but who knows.

Thanks in advance. I have seen a lot of 'turbo not spooling' threads, but I haven't come across one that distinguished no audible noise that wasn't fixed by the listed methods above. This forum has helped me through a lot in the past, don't let me down now, guys!

 

Was your turbo spooling to your liking before the issues you had with your car?
K03's are small turbos and their spool is barely audible especially if its stock non tuned.
Once a K03 is tuned which usually takes them to 15psi, the spool becomes noticeable.

 

Well since the turbo is directly connected to the exhaust I'd doubt the mech disconnected it... How sure are you that it's not spooling? Do you have a boost gauge(you should)? The K03 is tiny and with stock exhaust and intake it will not be very audible. With a large exhaust leak you likely got used to hearing it, with that closed up it's back to quiet again.

 

McGovs and George,

No I don't have a turbo gauge. On my list of things to do.

The spooling was audible before the exhaust fault. Not very, but enough at the point at 4500rpms to audibly hear the bypass valve working when shifting.

I called my mechanic and they also replaced flex piping at the catalytic converter if that adds any valuable details.

 

Your turbo is fine. The stock system hides the turbo sound as much as possible. When you had the leak, that's why it was audible, now its just back to stock so to speak so you wont be able to hear it.

 

yeah dude the turbo is fine. not being able to hear it is because of you getting the exhuast fixed. my k03 was always quite until it started to go bad. it whistled dixie after that

 

Thanks. I just assumed the since I could hear it previous to exhaust leaks that I would hear it now that it is back to how it was. 30,000 miles of audible turbo, and 3000 with exhaust damage just doesn't add up to me.

I also now do not have boost, or maybe very, very little boost, and was thinking maybe it is the N75 diverter valve, throwing my turbo into limp mode?

I will keep you guys posted. More input is also appreciated.

 

you didnt mention a lack of boost before. with this new information, id definately check shaft play on the turbo. it sounds like it may go soon and you dont want it blowing apart. the least amount of boost you can get is 4psi fyi.

 

Limp mode would likely cause a CEL. Do have VAGcom? I'm hesitant to believe "no boost" without seeing a reading on VAG or a gauge. Scan for codes if you feel you are in limp mode.

 

Contrary to everyone's doubts, the internal waste gate was stuck open, which attributed to me only hearing it spool in 1st gear with no power after 2nd.

The turbo has since been replaced, at my mechanic's expense, along with the catalytic converter. The car has never sounded or driven better.