Fifth Screw

I logged some data a couple of days ago. I don't see anything out of the ordinary but then I'm not an expert with this stuff. As far as I can tell, the timing, per cylinder retard, and mass air flow numbers look good.

This is a 99.5 1.8t A4 Avant Tip with APR v3.1, TT 710N valve (Bailey made no difference), and Borla exhaust.

Ambient temp. was 75 degrees. Humidity was somewhere between 55-70% or so. Power loss and surging was very noticeable under the heaviest load (going up a steep hill).

What I noticed is that the boost builds up quickly, the car feels fine through first gear and through 2nd gear up to about 3.5k rpm's. After that and well into 3rd gear, the car seems to lose power/boost. It feels like the boost drops off to about 8-10psi. Hard to tell exactly without a boost gauge though.

My dealer says they pressure tested the turbo plumbing on the intake side, but the tech didn't tell me that, the service writer did and that was not the first thing he told me, if you get my drift.

I still think I have a boost leak. Maybe one of the hoses to the intercooler has a problem. It's not obvious upon external visual insepection. When ambient temps come down, my car seems fine. It just seems to have a problem holding the highest levels of boost in warmer weather under load.

I've already replaced and tested the BPV and the vacuum lines from the BPV to manifold and the FPR line. Could a bad N75 cause this much power loss? I don't think it's the fuel filter, it would be more noticeable under all conditions, not just during warmer weather.


Here are the data files:

http://www.astraconsulting.org/LOG-01-002-003-020.CSV

http//www.astraconsulting.org/LOG-01-030-054-101.CSV

If you download them and load them into Excel, they are easier to read.

Thanks for reading!

-Adam

ModifiedA4

like this:

<img src="http://pictureposter.audiworld.com/143/vagplot-2.jpg">

(my graph of crappy g/s numbers)

Fifth Screw

I'm also trying to get APR to help me out, but I have not yet heard from them either.

ModifiedA4

x-y scatter chart, with lines. put the RPM on the x axis.