What the N75 valve does...

Pabs

Active Member
May 3, 2004
5,936
4
Basingstoke
I think it's rubbish - don't think adjustment is supposed to be done and could render it useless.
That said, if I have to get a replacement, it may be worth a shot just to see if it does work or not.
 

s1l3nc3r

ASBO car.
Jun 30, 2008
1,558
0
essex
I think the best way to have it "adjustable" would be to bypass it with a MBC but just leave it pluged in electronicly...
 

Pabs

Active Member
May 3, 2004
5,936
4
Basingstoke
This article has helped me a lot - it tells you exactly how the N75 works, and what it does.

http://forums.audiworld.com/showthread.php?t=1476692

pay particular attention to the last 4 lines of the article, which I feel apply if you are running a standard car.

On the other side of the argument - perhaps with increased boost (from a remap) the ECU's "messages" to the N75 are slightly askew from the factory configuration, and hence require tweaking? I'm not sure how accurate the factory calibration is, so wonder if you can get the N75's recalibrated???

EDIT: Re-reading this, if I've got my spare N75 at home, I'm going to fit it. If it doesn't cure the problem, I'm going to adjust it via the screw and see what happens. I think the key fact from research is that the adjustment is NOT a huge amount - it's a tiny turn of the screw in either direction. And from my mechanical experience, to bleed MORE air off by lifting the plunger (thus increasing boost by keeping the wastegate actuator closed) the screw would need to be turned CLOCKWISE. To decrease boost (and push the plunger down further, opening the wastegate) it'd need to be turned ANTI-CLOCKWISE.

I can't see how an N75 itself becomes "faulty". If it had a component that could wear, and thus leak (such as the OEM DV rubber diaphragm) then it'd make sense - as this seems to involve solid plunger & screw adjustment may well cure the issue.

Note: It seems that the screw is GLUED in place. In order to adjust it, without breaking it, the N75 needs to be warm/hot.
 
Last edited:

rsmith

Robbie
Apr 28, 2004
2,797
1
Tipperary, Ireland
This article has helped me a lot - it tells you exactly how the N75 works, and what it does.

http://forums.audiworld.com/showthread.php?t=1476692

pay particular attention to the last 4 lines of the article, which I feel apply if you are running a standard car.

On the other side of the argument - perhaps with increased boost (from a remap) the ECU's "messages" to the N75 are slightly askew from the factory configuration, and hence require tweaking? I'm not sure how accurate the factory calibration is, so wonder if you can get the N75's recalibrated???

EDIT: Re-reading this, if I've got my spare N75 at home, I'm going to fit it. If it doesn't cure the problem, I'm going to adjust it via the screw and see what happens. I think the key fact from research is that the adjustment is NOT a huge amount - it's a tiny turn of the screw in either direction. And from my mechanical experience, to bleed MORE air off by lifting the plunger (thus increasing boost by keeping the wastegate actuator closed) the screw would need to be turned CLOCKWISE. To decrease boost (and push the plunger down further, opening the wastegate) it'd need to be turned ANTI-CLOCKWISE.

I can't see how an N75 itself becomes "faulty". If it had a component that could wear, and thus leak (such as the OEM DV rubber diaphragm) then it'd make sense - as this seems to involve solid plunger & screw adjustment may well cure the issue.

Note: It seems that the screw is GLUED in place. In order to adjust it, without breaking it, the N75 needs to be warm/hot.

Pabs did you ever get around to adjusting the N75 via the screw in the top? just our of interest.
 

Pabs

Active Member
May 3, 2004
5,936
4
Basingstoke
I had a bit of a play with a spare N75 I had, checking in vag-com with really minor adjustments.

TBH, results were inconclusive - I *thought* it had done some good, and then the problem resurfaced - I don't know whether the car has the ability to adjust it's PWM signal to counteract anything I changed or not... but it didn't resolve any issues.

I'm going to go for an MBC soon I think.
 

rsmith

Robbie
Apr 28, 2004
2,797
1
Tipperary, Ireland
I had a bit of a play with a spare N75 I had, checking in vag-com with really minor adjustments.

TBH, results were inconclusive - I *thought* it had done some good, and then the problem resurfaced - I don't know whether the car has the ability to adjust it's PWM signal to counteract anything I changed or not... but it didn't resolve any issues.

I'm going to go for an MBC soon I think.

THanks, that saves me a pill of feic'in around with the valve, i must look into an MBC myself just to have more control over boost, although i thought i read somewhere they don't work that well on the 1.8t.
 
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