1.9 tdi 90 boost pressure sensor

[chris_90]

Hi guys noticed to day my boost pressure sensor is making a ticking noise on tick over and stops once it starts getting boost.

Any one no why it's ticking?

Can it be fixed or do I need a new one?

The car doesn't feel any different to drive so don't think it's causeing any issue as of yet.

[Crasher]

The boost pressure sensor on a 1Z is inside the ECU is is a virtually solid state passive part. Do you mean item 1 or 2?

http://i222.photobucket.com/albums/dd20/Crasher1964/G31Zenginebay_zpsfb592f47.jpg (http://s222.photobucket.com/user/Crasher1964/media/G31Zenginebay_zpsfb592f47.jpg.html)

[chris_90]

Sorry I'm new to these cars/engine

Its number 1 on that pic

[Crasher]

That is the N75 valve which controls the boost. This is a frequency modulator and opens and closes to control the position of the wastegate. I cannot remember how much they operate at idle, too long since I worked on one.

[chris_90]

Ok so probably best I get a new one then?

[Crasher]

No! If it is operating the ECU is doing it.... It needs to be understood if it is being operated excessively or if it is completely normal.

[chris_90]

Sorry that don't makes sense to me, so do I keep it? Or bin it and run a manual boost controller?

[Crasher]

No, just leave it alone! Is there a problem with the car?

[chris_90]

No issue at the moment, but the n75 valve is making a ticking noise at the moment

[Crasher]

If it is ticking the cars engine computer is telling it to. The ticking is allowing a small amount of modulated vacuum to reach the turbo's wastegate actuator and will be keeping the flap of the wastegate slightly open at idle to keep the boost where the engineers wanted it to be. The way the N75 valve works means that it will tick and the frequency will vary according to where the wastegate flap needs to be for a particular running condition. I was working on a 2009 T5 2.5 TDI the other week and the N75 on that ticked all the time and there was no issue. Which year and engine code (1Z, AHU or ALE) is your car?

[chris_90]

Right I see, mine is ahu, how do I go about upping the boost with this valve? No point at min but when I get more fuel in I will need more air to

[Crasher]

OK, the AHU does not use a vacuum as I said, it uses a pressure feed through the N75 to open the wastegate as boost rises. To be correct, in order to increase the boost you should have the ECU re-mapped to change the operation of the N75, or you can do what most people do and make a leak in the N75 to actuator pipe, some very sophisticated types even put on an adjustable leak!

[chris_90]

I've been talking to some one tonight and he said exact same thing about making it leak so that's something I'm going to try. Just looking in to.bigger injectors and a decent tuning box