What else cause 0.4-0.5 bar max boost

[Rusty]

What does VAG com say the atmospheric pressure is?

[shone190]

I am not that familiar with Vagcom, where I can see that, if it's not too complicated to tell?

[UrS4boy]

F96 Altitude/Barometric Pressure Sensor Information

You might want to check the connection to the F96 Atmospheric Pressure Sensor in the Urq. The AAN ECU wants a signal from it. With no signal, the controlled boost is reduced to zero, i.e. mechanical boost (which is all you are getting).

Here is some F96 info:

http://forums.quattroworld.com/s4s6/msgs/21892.phtml

[shone190]

Thanks UrS4boy, I'll check it today later, after work and inform You

[shone190]

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

OK guys, that's the situation I'll put manual boost gauge in car, disconnect the hose from N75 to WG and try the car again. There is no chance that I get boost greater than 1.3 bar, so definitely something mechanical is wrong

Do You have some ideas what to check now?

[UrS4boy]

OK guys, that's the situation I'll put manual boost gauge in car, disconnect the hose from N75 to WG and try the car again. There is no chance that I get boost greater than 1.3 bar, so definitely something mechanical is wrong

DO NOT DISCONNECT the hose between the N75 and the WG. DO that and there is NO control over the WG period. Just disconnect the electrical connection to the N75 and do your testing.

[shone190]

Without electrical connection I got only 0.4 bar as I should, mechanical boost.

This is definitely not normal at all that I can't get boost more than 1.3bar without N75-WG hose.

[shone190]

Does anybody know what can cause only 1.3bar of pressure without WG hose???

It means that there is no way at all that I can imagine boost pressure more than 1.3bar ever, with any kind of chip, MAP...

[prj]

Dump valve, blown check valve under manifold, incorrect cam timing.

[shone190]

I changed dump valve, so this is not problem, cam timing also can't be a problem, because everything work OK until some day

What do You mean by "check valve under manifold"??

[prj]

Check valve for breather system for manifold source. EVAP joins there as well. Plug that pipe on both ends and try.
Also timing can be a problem if belt slipped a tooth etc...

[shone190]

Thanks for directives, I'll try it and check timing cam too

[macspring]

Just read this thread because I have an intermittent boost problem.

http://www.s2forum.com/forum/showthread.php?t=66473

@ Shone190, what ever happened ?

Did you ever find a cure, or just burn it in disgust ?

Thanks.

[shone190]

Hi, no I never find what was wrong and now there is AHC 4.2l V8 engine in UR, I no longer have nerves to fight with problematic I5 turbo engines

[macspring]

Thanks for update. Is the V8 ok, or does that bring it's own set of issues ?