boost leak on 2006 a4 2.0t? data log inside

[estomax]

hey guys,

i just bought my buddys 2006 a4 2.0t 6speed because the dealer was going to give him peanuts for it. Anyway, i have known this car since new but now that its mine i am digging in and getting to know it. I noticed that it doesnt seem to really pull hard until over 4k rpm and did a boost log. It looks like i am not hitting peak boost until 5k rpm.. this is a 3rd gear pull so should have plenty of load.

I datalogged commanded boost, actual boost and RPMs in the graph below:


There are no engine codes besides an intermittent misfire and intermittent idle lean condition which may be unrelated but are not affecting drivability or setting off any CELs. The car has a Giac stage 1+? tune with catalytic converter coded out, since the car has had a test pipe for the last 15 years to hopefully make the turbo last longer.

My first thought is to go poke at the wastegate, since this symptom seems like the WG is stuck open..

Marko

[Jayz691]

I would def check the WG flap first. They commonly get worn and loose with age. Will cause it to underboost, or increase lag. Pop the TP off, and check it. Super easy with a TP, compared to stock cat.

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[a4audi4fun]

What mileage? - check for intake valves as they might need a carbon clean.

[Jayz691]

What mileage? - check for intake valves as they might need a carbon clean.

But that won't cause boost issues like this...

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[estomax]

its at 175k miles, (original clutch! lots of highway miles), my suspicion is wastegate flap too, i don't think a leaky diverter valve would allow boost up top right?

[Jayz691]

its at 175k miles, (original clutch! lots of highway miles), my suspicion is wastegate flap too, i don't think a leaky diverter valve would allow boost up top right?

Most likely not, but wouldn't hurt to pull it and check it out. Don't take long. And would depend on which one ya have. I had a sticky rev D, that would leak bad, then snap closed. But you would prob see more of a quick increase in boost. A pinhole in a rev G may act this way. Since its slow, like very laggy, id suspect WG leak, or weak actuator. Or maybe even a bad n75..

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[Alfonso@GIAC]

If you would like to PM the VIN of your A4, I can certainly check to see which file it was last flashed with.

Keep in mind if it is indeed running a "track only" file, we have not offered those files for almost a decade now so having a reflash done would throw a CEL if it has a catless downpipe.

[Theiceman]

shouldnt he be getting a P0299 code if he was underboosting ??