Too high boost pressure?

[driftin jo]

Jo, if I disconnect the n75 should I see 5 psi? Also if it keeps on at 2 bar what would that eliminate?

it would point to hose split or come off, waste gate diaphragm split or N75 jammed shut.

[nip]

You will also kill the turbo, comp wheel will explode as running very high boost and no recirc, when you shut the throttle the stress on the blades will be work hardening them, soon they will let go!
your intercooler and engine will be full of aluminium bits !

it would point to hose split or come off, waste gate diaphragm split or N75 jammed shut.

Cheers Jo il have a gander tomorrow

[WidowmakerS2]

Your car is chipped and ecu has a different map sensor.

Well, yes..

Disconnect the N75 (electrical connector) and tell us what your gauge reads

Will try to unplug the N75. I also have a few other ECUs that I can try.

I'm running with no resirc because I don't have the hoses for it. Will sort this asap.
Also hoping this will sort the issue with car stopping at intersections/red lights.

It could be one or more of the reasons that has been described earlier. I have no idea what pressure it was running before, but I know it hasnt done too many miles with this pressure (engine has only run 500km since overhaul, wg/turbo is from a different car)

[UrS4boy]

Disconnect the N75 (electrical connector) and tell us what your gauge reads

Agree. Nip should disconnect the *electrical* connector on the N75 Waste Gate Frequency Valve (WGFV). He should then see only the mechanical boost pressure provided by the WG spring. Stock, this would be about 6 psi (0.4 Bar). With an 034 1.9 Bar (absolute) spring, it would be higher, at about 12.8 psig (0.88 Bar). IF the boost pressure is higher, then the hose between the N75 and the lower chamber of the WG is torn or missing *OR* the WG diaphragm is torn/leaking with the end result being there is no pressure available to lift the waste gate piston off its seat and, thereby, dump boost. This engine is going to the max followed by "KA-BOOM".

N75 info here: http://forums.quattroworld.com/s4s6/msgs/20987.phtml

[nip]

Agree. Nip should disconnect the *electrical* connector on the N75 Waste Gate Frequency Valve (WGFV). He should then see only the mechanical boost pressure provided by the WG spring. Stock, this would be about 6 psi (0.4 Bar). With an 034 1.9 Bar (absolute) spring, it would be higher, at about 12.8 psig (0.88 Bar). IF the boost pressure is higher, then the hose between the N75 and the lower chamber of the WG is torn or missing *OR* the WG diaphragm is torn/leaking with the end result being there is no pressure available to lift the waste gate piston off its seat and, thereby, dump boost. This engine is going to the max followed by "KA-BOOM".

N75 info here: http://forums.quattroworld.com/s4s6/msgs/20987.phtml

Disconected the n75 today am now seeing 1 bar sometimes creeps to 1.2 bar

[UrS4boy]

Disconected the n75 today am now seeing 1 bar sometimes creeps to 1.2 bar

Wow. That is some "stiffer" WG spring you are running. I would suggest TOO stiff as it gives the WGFV very little room to work properly.

[nip]

Wow. That is some "stiffer" WG spring you are running. I would suggest TOO stiff as it gives the WGFV very little room to work properly.

im going to find a standard spring to use cheers

[WidowmakerS2]

My problem seems to be exactly the same as NIP's. I'm seeing 1 bar mechanical boost.
Changed the diaphragm yesterday, and I could swear it looked like the original spring.
Also changed the hose from the lower chamber to N75, as it had a nasty bend in it.

[nip]

My problem seems to be exactly the same as NIP's. I'm seeing 1 bar mechanical boost.
Changed the diaphragm yesterday, and I could swear it looked like the original spring.
Also changed the hose from the lower chamber to N75, as it had a nasty bend in it.

Mine dont do it now, it was the n75 that was plummed in the wrong way.
I do get boost creep tho in 6th it creeps to about 25psi on full throtle, id say check the n75

[bigcooler]

slightly off topic but how bad would it be to find out that you have been running 2.5/2.6 bar with standard internals

[Donatas]

hey my N75 always is open 1 port from turbo to wastegate. i give + from battery to my n75 it is ticking but 2 port from turbo to turbo intake hose does not open when i try with my mouth blow. so it is big problem that not open second port and i need change my n75 or leave it ? when i push pedal to the flor my trip computer shows me
2.1 - 2.2 bar real bar is 1.1 - 1.2 so its good. what consequences kann be that not open port from n75 to turbo intake hose ? i think u will understand,my bad engl skills.thx

[newsh]

It never opens from turbo to turbo inlet hose, this is normal.
The 2 states are..
1/ open from turbo to WG
2/ open from WG to inlet hose