There's a long story behind it, but suffice to say old turbo was producing the "dentist drill" whine very loud, very low boost, then one day no boost, no whine.

Broker I bought the car from originally put in a "new" turbo (I have no idea of the origin). Now car has boost, although people with experience in these cars says it's less boost than one would expect. Also, still makes a whine, although diminished in volume. But it's a whine you can clearly hear in the cabin, and actually also from outside the vehicle (which I'm also told is highly unusual).

The car is a 2003 A4 1.8T Avant.

Any thoughts/diagnoses? Advice?

 

Theres no way to actually diagnosis this without hearing the car and feeling how hard the turbo pulls.

 

I would recommend putting in a boost guage to see what you are actually getting out of the turbo.

 

Can I get away with a temporary gauge in-line at the intake manifold and just rev the engine in my garage? Or do I need to measure boost under actual driving conditions?

Any good links for ways to install boost gauge? Car does not have boost instrumentation.

 

You need to be driving the car to see how much boost you're really getting. Here is a DIY on how to install one. It is a very simple install as long as you are at all mechanically inclined.

 

I ordered the AWE Tuning Center Vent Boost Gauge Kit the other day. I'm not a hardcore DIY, but I'm mechanically capable, so I'm going to give the install a shot myself . Thanks for the feedback. I'll update thread if anything interesting results that could be of use to others (i.e., boost is indeed low, or the whine is indicative of larger issues).

 

AWE Vent Boost Gauge kit arrived yesterday, installed today. Was not as easy as many have made out... They sent the "T" for a 2005+ A4, but I didn't realize it was the wrong one until everything was in pieces on my garage floor. Thanksgiving day. Thank goodness a car parts store about 10 miles away was open, took the other car and got a "T" that seems to be working. Plus, the hose was too short and the ground recommendation was impossible to reach. Blah blah blah. Finally got it hooked up.

Put everything back together, started the car up, boost gauge did it's full cycle dealy, then settled in around -10 psi at idle initially, then when it warmed up it seemed to be steady at around -17 psi at idle.

Drove around the block a couple times to warm the engine up, then pushed it to boost and it consistently topped out at 10 psi under load, never exceeded that number. Still makes a whining noise. Not too loud, but definitely there.

The boost gauge is tapped at the vacuum host on the front of the intake manifold.

So, that boost number seems low, from what I've read. Time to take it back to the mechanic who installed the new turbo?

 

I have heard of a lot of problems with these models, someon I knew had their cambelt go, despite it being changed at 60k at 90k. that's pretty bad.

 

That's so helpful. Thanks for the feedback. A positive wealth of information. You're obviously very knowledgeable and an expert on Audis. You even have a single anecdotal story about someone you know who once had a problem with an Audi A4.

Now please go away.

 

The more I read, the more it seems ~10 psi is actually full OE boost for this year. In a different thread, "cincyTT" posted:

Model Years: 2001-2005
Compression Ratio: 9.3:1
Horsepower (SAE Net): 170 @ 5900 RPM
Torque: 166 ft. lbs. @ 1950-5000 RPM
DP Size: 50mm
Turbo: K03s
OE Boost: .6 Bar = ~9psi

That's a relief. Seems like I'm rolling now. Car is in great shape, everything (important) works. Just a few pieces of trim to replace, tailgate solenoid is unpredictable. But the snow is falling in the mountains, and I can't wait to go test out the quattro in real conditions. In the Spring, I'll think about Stage 1 chip upgrade. New wheels/tires. Tint.