Phil White

This is the first time I've logged my XR chip, and it's putting out some crazy boost!

I find it odd, however, that the actual boost is always well above the requested. It almost looks like the ECU is lowering the requested boost to try to compensate, which may be why I'm getting a "boost pressure control - negative deviation" DTC. Any ideas?

<img src="http://pictureposter.audiworld.com/10463/excess_boost.jpg">

s4what?

If so you are putting out 1.5 bar (relative). That does look like a problem with the wastegate.

Phil White

I agree that something is definitely wrong. I need to do the same log with the stock chip and see what happens.

System_S4k

Positive devation is to much. Something isn't right.

Phil White

I'm going to go check for DTCs again. That log was taken after I cleared it out, and I didn't check again after making the log (my laptop ran out of juice during logging). I'm thinking that DTC may have been in there previously...

OK, sure enough: no DTCs, even after taking it out for another run.

triada

why is that making more than it's asking for? i read somewhere that the factory computer sensors only can see up to 2500mbar too. try the stock one and see if it still goes ape-dung like that.

s4what?

In absolute terms a stock ecu would be 1.7 bar, aftermarket would be 2.0 bar. I guess the tuners and boost gauge manufacturers are using this measurement incorrectly.

DAP@EPL

I had a friend with a Jetta 1.8T that was overboosting just like that graph shows (execpt it was the stock ECU). He was also getting a negative deviation DTC. The dealership indicated that it just mean there is a difference between the requested and actual boost and isn't always a lack of boost that sets that DTC.

Signs pointed to a funky N75 valve, but he traded the car in before we could diagnose it further.

-Dave Pramanik