N75 H

Started by URS4 Avant, November 30, 2018, 12:26:18 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

URS4 Avant

Anyone have a known to be good N75 valve for a URS4? Mine has got very lazy and boost spikes when i put my foot down to dangerous boost figures. Had to take it off and use a manual valve but would prefer the N75 H. 034 906 283 H.
Thanks Kevin


You say "dangerous boost figures", what is dangerous boost figures?

1.8 bar is normal for an auto, 2.1 for a manual (from memory), in both cases maybe higher if chipped, 2.3 - 2.4...

Unplug the N75 power source. You should get 1.4 bar boost max on a stock vehicle with a stock spring if the waste gate is functioning properly. The car will run like normal but with 1.4 max boost. You can safely drive the vehicle with the N75 unplugged.

Post back results.

See link below.


Consult that forum for expert advice.

89 Coupe

URS6 manual runs 1.8 bar factory (indicated boost is +1 bar atmospheric pressure, when the engine is off with the ignition turned on)
1991 BMW E34 535i | 1989 Nissan Skyline R32 | 1993 Nissan Skyline R33 Coupe | 1989 Audi Coupe Quattro | 1996 Audi UrS6 | 1994 BMW E34 540i Touring | 1995 Audi 80 Quattro Avant | 1993 Audi UrS4 Avant | 1999 Audi S4 | 2009 Audi S8 | 1995 Toyota Cresta JZX90

le mans

I doubt the boost spikes would be a major problem - ecu should cut fuel/ignition if boost goes too high.

URS4 Avant

With the N75 unplugged yes it goes fine, re: boring! If it is plugged in and say if im in 2nd gear and stand on the throttle the boost shoots past 20psi and the car breaks up and sounds terrible (not done to many times..) If im in 2nd gear and slowly depress the throttle till i get to full throttle the n75 copes. Its like its working but not fast enough to regulate boost when i jump on the throttle. With the manual controller i have it got to boost 16psi max which is fine (i have a new innovate air/fuel gauge which shows 10.6 afr on full throttle) but the boost quickly tapers off. The n75 when it was working properly holds on to higher boost through the rev range and makes for a quicker car. 
No spares then! oh thanks for the replies.


Unfortunately the N75 H valve is NLA. But before you blame the N75 there are a whole bunch of things that you can also check. Cleaning electrical contacts of the various sensors under the hood (with a can of contact cleaner) is a good start, I had a weird idle issue that I finally solved by doing this last year.

You might want to start by cleaning the MAF electrical connector.

A boost leak can cause the bucking issue at WOT if that is what you are describing.


URS4 Avant

Hey, thanks user2154 for your reply.. Just to make myself a little clearer i guess, i have installed a good quality boost gauge and a innovate air fuel gauge. The car has been performing perfectly with the manual boost valve. When i plug the n75 in it is the only thing that introduces the initial boost spikes. I do not get any codes from any sensors, and the MAF terminals are as they should be. I have also tested the MAF resistances with a multimeter. Has been boost leak tested also. I believe this leaves the N75, i can still buy a new one from 'audi tradition' but was feeling a bit cheap! When i buy a new one i will let you know how i got on  :)


Where did you tap in the new boost gauge? I would disconnect the new boost gauge and put it back to stock. Your ecu map sensor may not be receiving the correct pressure for some reason.

You can test the resistance of the N75, check the link, cannot vouch for the figures being correct.


You can also run output tests which will cycle through various modules and you will hear the N75 click on and off, but it sounds like it is working (but maybe incorrectly) from what you describe.

So you installed a wide band O2 sensor or just the gauge? Did you calibrate the wide band sensor in fresh air, and did you install it 24 inches downstream from the turbo as recommended?

How much is the N75 at Audi Tradition? You might find one cheaper by asking at forums.quattroworld.com/s4s6


Found one for you mate, PM'd you

edit: sorry that is for 1991 Audi 200, might be different, don't know