Hi,

I've got a 2002 Audi A3 1.8T (KO3 sport turbo, DWB, VCT) and recently installed a chip. The car is stock standard except for the chip and it has a new green top coolant sensor, new OE Bosch 710N DV, N75J.

The car surges dslightly during part throttle (2800rpm-3800rpm) and I would like to know what can be done to fix this. I've tried the F and J versions of the N75 and it doesn't make a difference.

I recently fitted a boost gauge and it showed that I boosted around 1.1bar peak at 3000rpm and tappers down to 0.6 bar at the red line.....so boost is not really that high.

During the boost gauge install I noticed that the gauge buzzed and I got the advice to fix it by adding some sponge in the line right after the T piece. This solution works great and I'm now starting to think that this might also be a solution for the surging!

As far as my knowledge goes the N75 controls the waste gate by means of pressure and people change them because some of the respond slower/faster and thus solving surging problems.

My theory now is that if I put a piece of sponge in the exiting line of the N75 that goes to the waste gate it should soak up any fast pulsating pressure signals to the waste gate and maybe smooth out things a bit. Do you guys think that this is a dumb idea?

Only problem that I can forsee is that the ECU might try to compensate to much if response is too slow to the waste gate...this can however be modulated by adding more/less sponge in the line. The reason why I'm not too worried about this is because different N75 have different signal speeds and this see

PS: The sponge I use is the plain old 3M yellow sponge that one uses to wash dishes


What are your thoughts regarding this "plan" of mine?