N75 Valve on 20vT

The N75 valve controls the levels of boost created by the turbo. It does this by controlling the actuator that opens the wastegate, allowing pressure from the exhaust gases to be either used to run the turbo or flow through the exhaust or into the atmosphere, depending on the set-up.

There are several versions of this valve, fitted to different cars allow for a different adjustment of boost. Reports state that some handle higher levels of boost whilst others maintain boost for longer but with a lower spike.

The common ones are

N75j 034 906 283 J
N75h 034 906 283 H
N75F 058 906 283 F VW and others
N75C 058 906 283 C

034906283H is used by Audi 100/Avant quattro, S6 : 1991-1997 2.20 l, 230HP engine AAN
034906283J is used by Audi quattro : 1989-1991, 2.20 l, 230HP engine RR; Audi S2, coupe, 80 : 1992-1995 2.20 l, 230HP engine ABY; Audi 200, coupe quattro : 1989-1992, 2.20 l, 220HP engine 3B; shape is like 034906283H
034906283K is used by Audi Avant quattro, coupe quattro : 1992-1996 2.20 l, 230HP engine ABY; Audi RS2 : 1994-1996 2.20 l, 316HP engine ADU; shape is like 034906283H

Mine had on it the F valve and was spiking on boost, I could have replaced it with another new one or tried something else so I have gone with a J.
Fitzy ordered it for me, it was awkward as it is not a VW part.
It arrived today and I fitted it quickly. Slightly different in the fact that the wire connection points backwards not forwards. The longest arm goes into the TIP and the other two short pipes go to the actuator and one to the hot side of the turbo. It does not matter which way round these two go as they are essentially joined.

I will get pictures when it is lighter.

A test showed it to be smoother with no unexpected surges, will test more tomorrow to see if it actually has a higher boost.

I have used this for 150 miles today.
Smooth but strong boost from very low rev, no noticeable surge anywhere but a lovely amount of power.

Friend's got a Skoda Octavia RS and wants to start doing little things, where's the best place to look up the facts behind N75 replacement?

There is not a lot more to it, I will post a few pictures so people can see what the part is but it is about undoing the old one from the Turbo Intake Pipe, then the two small pipes to the hot side and actuator. There is a electrical clip and then you are done.

What other facts does he need? The replacement should not be a problem for a car that is healthy but can throw a limp home mode if there are boost or vacuum issues.

I can show you on Thursday night.

Cool, just wondering how you decided to go for a "J" rather than any other one in particular

Ah
OK, the F is said to be a smooth polite boost profile. The C is similar.
The J can have higher spikes but is still meant to be smooth.
The H has higher spikes again but is more aggressive and may not hold it for as long.

I wanted to add something that move the car to a more sporty map and will tie in with the other changes I have done/doing. The J seemed like a good half way house between smooth and aggressive.

I have worked on my pipes so know it can handle a bit more boost.

I have bought another N75F valve.

It does not boost as early and pull as hard but goes on pulling to a point of extreme excitement.

Anyone wants to play with the N75J then let me know.

me?

geoff i feel bad for having your old f off of you

jimbo fix your boost leak!

OK Mr Wild, you can collect or get it off me at the next meeting. Fitting is free if you have the right clips .

No worries Mr Sparkie, I was alway going to order a new one to see if it cured a problem.

If there is a boost leak, lets get it fixed.

Agh this thread is making me want to look at my valve! Could my surging issues be caused by a faulty N75? What's the best of checking??

The only way to truely test an n75 is by replacing it, if you have a fault code for over boost or lack of boost then this would b a good indicator

Sorry posted on wrong thread, but will be checking my n75.

The K version of this valve. Anyone know what it's like compared to your J version?

Fitzy wrote:

The only way to truely test an n75 is by replacing it, if you have a fault code for over boost or lack of boost then this would b a good indicator

Even if the lack of boost fault comes up on idle ?

What error are you getting?
What Fitzy is trying to say is that the N75 is a pretty dumb valve, if it is failing you get a warning sign. Symptoms of failure are jittering as the wastegate isn't smoothly actuated.

As for the J valve, I never tried one.
The more I understand what these valves to, the more I think we should keep the correct one for our car and just get a good remap. The more aggressive they make and break boost via the wastegate, the more aggressive the car will feel to drive. You won't actually get more power, just the sense of it. As my car can wheel spin into second, I think the two wheel drive and gearbox are the next weak point rather than this valve.

Well turns out I had a sh*t map on the car but all good now and 241.8bhp I'm happy.

With 241.8 you should be very happy. Who did the map and what PSI are you now seeing on boost?

20psi on boost and I went to see niki at R-tech in Leicester he also give me launch control rapid lift pop bang and I get flames. 273ft/lb. full custom map and niki is a sound dude.

I am more impressed by 273ft/lb than 241.8 bhp, that must be quite a launch.
How does the launch control work? I am expecting you need it.
Your car is certainly coming together as a beast.

I am only getting 18 psi before my turbo actuator opens, when I am not so damn busy I have got to swap it out.
The next problem was the insurance company wanting to increase my premiums by a horrific amount.

Oh. Yeah it moves love spitting flames too.