Turbo surge

[jannie6]

Hi guys, I am new to this site, I'm hoping that someone could answer my question or maybe just give me some advise.

I have a 2005 Audi A4 b7 2.0tdi 140 with 118k miles on the clocks. I get turbo surge on accelerator lift off. The car has never done this when I bought the car, only started doing it about 5 months after I got the car. (also need to mention that this is my first diesel car)

I have reconditioned the turbo, I have a brand new egr bought from Audi, and a brand new N75 also bought from Audi, but the turbo still surges and that annoying sound irritates me.

Is there anyone out there who can tell me why or how this problem all of a sudden just appeared, and is there anyone who can tell me how to fix this problem?

Any input from anyone would be greatly appreciated.

Thank you

 

[DieselJake]

DPF issue? Any vag-com codes?

 

[jannie6]

As far as I know the 140 doesn't have dpf, only cat, and my car has been scanned by two different places and not one of the two scans showed any fault codes

 

[jannie6]

Could a blocked catalytic converter cause an issue like this?

 

[jannie6]

In this link is an exact same example of what mine sounds like



But I will still try and upload a video of my own car aswell

 

[SDHA4SLine]

I have no idea but jeeeeesus that is a racket

 

[DieselJake]

Sounds like a breathing issue in that video, would kind of add up as you can see his K&N filter. Aftermarket filters are not a friend of diesel VAG engine's.

 

[SinghB7]

I have a sound from the turbo wen I lift off the accelerator altough I have a 2.0tdi 170, it use to make a quiet noise I beleive its just the blow off valve but since havin it mapped and adding a pipercross filter it has gone louder altough no boosting issues. Sounds kinda cool lol

 

[SDHA4SLine]

I have a sound from the turbo wen I lift off the accelerator altough I have a 2.0tdi 170, it use to make a quiet noise I beleive its just the blow off valve but since havin it mapped and adding a pipercross filter it has gone louder altough no boosting issues. Sounds kinda cool lol

Blow off valve, you should have a diverter valve on tdi and you shouldn't hear it unless your cars been modified in some way to have blow off valve which will gain you nothing and possibly make turbo spool time longer...

 

[DieselJake]

Blow off valves on diesels bad news is the issue is the issue could easily be related to your aftermarket filter which may have caused some serious damage.

 

[jannie6]

My car is still stock standard, no mods, no maps, no aftermarket filter, I can hear the noise when driving, but can hear it much clearer when I disconnect the airbox from the intake pipe, this noise was never there before

 

[desertstorm]

The noise is generated by the VNT mechanism in the turbo being closed and opened rapidly in response to rapid changes in boost requirements.
There isn't a dump valve as such on these cars the VNT mechanism controls the flow of exhaust gas through the turbine part of the turbo.
issues with the N75 or vacuum leaks in the system can cause changes to the control and you could end up with similar noises to that above.
You need to do some diagnostics with VCDS and a vacuum gauge to see if you can locate the problem.
May also be due to the VNT mechanism sticking due to being carbonned up.

Karl.

 

[jannie6]

Thanks alot desertstorm, I thought it had something to do with the n75, and that's why I bought a brand new n75, and didn't solve the problem, it shouldn't be vnt sticking either, because the turbo is reconditioned, so I assume that they would've cleaned everything, but my next step will definitely be to check the n75 duty cycle, but what are the chances of that going out by itself? Unless the actuator rod position maybe went out by a ball hair due to wear as the car aged? I will definitely check all of that, thanks alot for your input karl

 

[SDHA4SLine]

which N75 did you replace, N75 Solenoid valve or the N75 pressure convertor?

 

[jannie6]

I replaced the pressure converter, I think the solenoid valve and pressure converter is one thing, because there is nothing else connected between the main vacuum feed and the actuator, and my n75 only has two pipe connections, and not three like the b6 has

 

[SDHA4SLine]

Yes that's the N75 pressure converter, but there is also the N75 Boost Solenoid valve Part No. 1K0 906 283 A <--- this part number is for my 2.0TDI 170 so please check it if you do want to changed that valve also

For my car, the solenoid Part number No.1J0 906 283 C has been superseded with the number I mention above. I still have the old one & if you are local and want to pick it up you can have it for FREE. It works fine, I replaced it trying to resolve some running issues which turned out not to be the solenoid valve!

 

[jannie6]

Unfortunately I'm from south Africa, hahahaha, but thanks for the offer. Where is that boost solenoid situated, and can you please send me a photo just so I can see what it looks like and see if I can find it, please man

 

[SDHA4SLine]

Oh dear that is a little far.

Unfortunately I cant tell you where it is as I paid a garage to fit both of mine!!!

I was going to take a picture to put on this forum for other peoples benefit but the mechanic said good luck mate its underneath the car above the under tray...

However they do appear to be located in different places on different models have you looked at your bulk head? heard of them being bolted to there before, you may be lucky.

This is what you're looking for

 

[jannie6]

Okay nevermind, I had a look now, that is the same part number for the one in my car, but that one goes to the egr actuator in my car, could the egr have anything to do with the boost?

 

[SDHA4SLine]

Got to be honest, I don't know, best wait for the more technically gifted guys to reply.

Sorry

 

[jannie6]

They are mounted to the same plate in my car almost next to each other, it's a huge mission to replace them, I had to take off my whole belly pan to get there, they are mounted to a bracket plate which is mounted to the side of the engine block above the sump

 

[jannie6]

I still think that karl is spot on with my issue that I'm having, car has no boost problems, runs fine and no fault codes, so it could only be the n75 cycle which could be a bit off which I will have looked at as soon as possible

 

[SDHA4SLine]

Yes he's given me some good advice before I would trust his opinions

 

[aqibi2000]

Bump anyone get to the bottom of this?

The only vacuum driven actuators left on the vehicle is the N75 and the small valve which drives the inlet flap (it too is not leaking)

Turbo actuator holds vacuum well, as does the N75. Tightened the IC Clamps too.

It's difficult to diagnose since it only happens when driving under load. Underoad I hear the BOV type squeal noise when letting off the throttle.

Have since also replaced the exhaust manifold gasket and turbo to down pipe gasket, turbo has absolute minimal play.