engine stumbling/hesitating at WOT

[Jamo]

Sounds like boost spikes to me, if you put the stock WG spring in does it not occur?

if this is the case the chipset can't handle the speed the boost is coming on, I bet it's the 034 chipset?

Ross used to see this on his car on the dyno yet on the road the boost spikes never occurred

[archiboy24]

If its a 3B with a dizzy check the static timing very carefully as if the hall sensor window in the dizzy is not exactly lined up at TDC the ecu can mistake this for pinging (detonation).

Puff of smoke is unburnt fuel, either ignition related (high boost is killing the spark, poor spark plugs, leads, pos or coil packs) or pinging and the ecu is chucking in extra fuel to put the fire out..

Timing is dead on. It's more a cloud of dust than smoke. Very light in color, as you'd expect road dust to look like when hit with 15-18 psi of air. Only noticed it once or twice. The spark plugs (stock F5DPOR) are about 3-4 years old and have about 20k kms on them. Perhaps they should be changed. Plug wires look to be original. Perhaps they should be changed as well!

[UrS4boy]

Sounds like boost spikes to me, if you put the stock WG spring in does it not occur? if this is the case the chipset can't handle the speed the boost is coming on, I bet it's the 034 chipset? Ross used to see this on his car on the dyno yet on the road the boost spikes never occurred

I agree about the boost spikes. On another forum, I suggested to Ben that his 1.9 Bar WG spring might be wound in too far. I had that happen with my RS2(+)'d AAN. At WOT, the rate of boost rise was too fast and not even the MRC s/w could cope. The ECU dumped the extra boost, then reset, asked for more, then dumped, then reset, then...etc. (all in fractions of a second) so the result was a nasty jerking miss feeling. The cure in my case was to turn the 1.9 Bar WG spring all the way up.

On a related note, I dynoed the car with the 1.9 Bar spring (turned in too far before I figured it out as per the above). The dyno results were bad because of the jerking boost cycle thing. Solution for the dyno runs was I reinstalled the stock spring. Made more HP on the dyno. However, I liked the snap of the 1.9 bar spring and a few days later, reinstalled it. This time with the spring perch turned all the way up. Works a treat.

Here is a link to the post I made about the two dyno run sets:

http://forums.audiworld.com/showthread.php?t=2162171

(Note: The label on the non-stock WG spring graph should have said 1.9 bar not 1.8 bar)

[archiboy24]

As you guessed, the problem seems to be with the wastegate spring. I installed the stock spring with no turns on the adjustment screw and it ran fine. I then adjusted the tension one turn at a time and it seems that 3 turns is the limit. Anything beyond that triggers the boost spikes. For some reason it doesn't like the 1.9 BAR spring.