What else cause 0.4-0.5 bar max boost

[AndyP]

Boost test kit came and there is no boost leak in system. So I really don't know what else to do

I tried to change from other car (URS4) which boost 1b as it should be:

1. N75
2. Dump valve
3. ECU
4. MAF
5. Changed all vacuum hoses with brand new
6. Moisture trap
7. New turbo hose from Maf to turbo
8. TPS
9. No boost leak
10. disconnect MFTS

This is really nightmare

Does anybody know what else should be the reason for this?


@UrS4boy
ECU pinouts for AAN and ABY are the same:

http://forums.quattroworld.com/s4s6/msgs/21009.phtml

http://s2central.net/main_frame.html

Try pressure testing the vacuum hoses, take all 3 off the back of the inlet manifold and test like this:-

http://www.s2forum.com/forum/showpost.php?p=465355&postcount=4

[shone190]

I've changed all vacuum lines, so I doubt that it's a problem

[newsh]

Have you done output tests to see if the N75 is actually working?

[driftin jo]

Waste gate jammed open.

[Christophski]

Mine was a faulty waste gate mate.

[shone190]

How to "test" wastegate?

[Christophski]

Umm, I just got a second hand one and fitted it and it fixed my issue. I had done lots of other things and it was about one of the last things it could have been. Sorry I cant help with how to test it mind you when doing a boost leak test I could hear it hissing from in that area.

[driftin jo]

Dissconnect the hose from the N75 to the waste gate, if the waste gate
Is ok you will get boost very quick. If it does make more boost Don,t hold
It At wide open throttle, Back off as you don't want uncontrolled boost.
If it is the sane as before Your waste gate is jammed open and needs fixing.

[shone190]

I tried that before and get boost very quick to 0.8 - 0.9b, so it's not the problem

[prj]

Boost very quick to 0.8 - 0.9, and after that?
It should make 2 bar really quick, not only 0.8-0.9.

[shone190]

I didn't try anything more than that, but I'll try today

[prj]

I mean, if you get 1.5, ok let off.
But if all you get is 0.8 bar then something else is wrong.

[shone190]

OK, I'll try later when I came home

[shone190]

I just tried the car without N75 - wastegate hose and boost goes more than 1b very easy. My stock boost digital gauge have max 1b on scale, but I feel that boost goes more than that The car is going like motorcycle

So guys, what do You suggest next?

[driftin jo]

Ok, it's not your waste gate, have you checked the N75 wiring, have you done the output tests ?
Do you have vag com ? You can do the output test without vag com if you don't have it.