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Discussion Starter · #1 ·
Does anyone know at what pressure the wastegate should start to move on a 2.5TDi AJT engine please?
 

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Discussion Starter · #3 ·
Mine doesn't start to move until 0.5bar/7psi.

Do you reckon the turbo recon company have set it up wrong?
 

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How would anyone know when their wastegate starts to move?

My AJT generally sits at between 0.6 and 0.8 bar depending on revs etc.

I don't actually know when the turbo is being held back by the wastegate or whether it just doesn't have enough exhaust pressure to drive harder, or the inlet flow is too high for it to maintain the pressure (at higher revs)?

I suppose I could watch the control signal with VAGCOM so at least then I'd be able to see when the ECU was demanding a reduced boost.
 

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Discussion Starter · #7 ·
How would anyone know when their wastegate starts to move?
You can connect a Mityvac (or similar) to the tube coming off the wastegate actuator and apply a pressure. You then just keep pumping up the pressure until you see the actuator starts to move, then check the gauge for a reading.

I've got the dreaded overboost fault code coming up and am just trying to work through possible causes.
 

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I think that is for direct acting (simple) wastegate turbos - the one on the AJT is ECU controlled so the pressure required to physically move the actuator is not when it will be acting.
 

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Discussion Starter · #9 ·
I was under the impression that the actuator rod is held closed by a spring, so a fair amount of pressure is required to act against it to open it :*

Can anyone who has used vagcom to pulse their n75 please tell me if you can hear the solenoid move (like the n18 egr does), or does it just move the actuator on the turbo up and down?

Thanks T:
 

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Discussion Starter · #13 ·
I'm basically trying to find the cause of my overboost.

It's odd that it's only started to happen since I fitted a reconditioned turbo, so I'm presuming it's because the actuator rod has been set incorrectly. Having said that, my old turbo couldn't pull the skin off a rice pudding, so it couldn't overboost even if it tried. Therefore it is possible the problem was there before but disguised by a knackered turbo.

I've got a brand new N75 valve, so it shouldn't be that, and all the all hoses are all plumbed up correctly as far as I can tell.

I'm afraid it's just another of those "I've got an overboost problem" threads :)
 

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If your 100% that your turbo is working correctly, and the n75 is fine then what next...

Thinking logically about this it can only be 2 things - faulty reading or uncontrollable boost.

Faulty reading could be bad wiring, faulty MAP sensor and duff ECU.
Have you fitted a boost gauge so you can see if the over boost is real?

If so, and it is, then maybe you are over fueling?
I've read that with cheapy tuning boxes turned full up it's possible to generate so much exhaust pressure that even with the wastegate open the boost is more than requested.

Just throwing a couple of ideas out thereT:
 

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Discussion Starter · #15 · (Edited)
Thanks for your ideas.

The turbo spools up lovely. You can really here it spinning away.

Unfortunately I don't have a boost gauge fitted, so can't compare a guage reading to a vcds log.

Other than the overboost fault code, there are no others so I think the MAP sensor is ok. However, I will check it out to double check.

I don't have a tuning box fitted, so it can't be that.

There's no sudden loss of power or glow plug light flashing when it happens, just a noticeable loss of pulling power when you come to an incline! Turn the ignition off and back on, and everything is fine again until the engine is next under heavy load.

I know my timing is slightly retarded, which I'm planning to sort out in the next couple of weeks.

I'm also running PP2 injectors so the fuelling isn't perfect yet as I need to get a remap done. I'm hesitant to travel all the way up to see Chipwizards with this fault though just in case it's not the fuelling that is the cause. If a remap will cure it then brilliant, but it's a long round trip to find out!
 

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I'm also running PP2 injectors so the fuelling isn't perfect yet as I need to get a remap done.
Ah, new information surfaces :D

So it could well be over fuelling then.
Have you asked Rake if others have suffered from this prior to the remap?

Also I can only just hear my turbo spool up from in cab (no windows open etc).
Do you still have a standard air box?
 

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Hi

I've had issues with severe lack of power especially on the hills. The actuator rod was stuck and the n75 valve was not correctly connected. Handed the van to sjm autos near by and now its flying A: the timing was also corrected, may be worth giving them a call. hope this helps.
 

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Discussion Starter · #18 ·
So it could well be over fuelling then.
I guess that is a possibility
Have you asked Rake if others have suffered from this prior to the remap?
I haven't, but that is definitely worth finding out.
Do you still have a standard air box?
Yes

I've had issues with severe lack of power especially on the hills. The actuator rod was stuck and the n75 valve was not correctly connected.
My actuator is free and N75 is connected properly (to the best of my knowledge). But thanks for the garage recommendation. I'll definitely bear them in mind for getting the timing tweaked.

Thanks both for your comments and suggestions T:
 

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Hi Snake,

Regarding the PP2's and over boost.
I would love to be able to say that I have come accross this before but in all honesty I have not seen it in combination with the injectors.

PP1's flow more fuel and I havent seen it with them either so in my opinion - the cause is not the injectors but rather something else that maybe exacerbated by an increase in performance.

Now just looking at some practicalities.

You say this only really began since fitting a recon turbo. It is highly possible that the actuator needs setting correctly.

Where did you get it from ? can you ask for them to check the actuator setting ?

What fault codes does she throw ?

The duff turbo you had before may have been masking a pre existing issue.

It may well be worth checking some of the vac com data for the sensors too - actual Vs Expected values should not be very different from eachother and sometimes dont throw a code such as temp sensors MAF MAP etc. May be worth a try.
 

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Discussion Starter · #20 ·
I got the turbo from AET turbos in Wakefield. I can't say I've much confidence in them to be honest as the first time they sent me the turbo, the feed and return lines were 180 degrees out. Thankfully I noticed that whilst it was "on the bench" and not already bolted in the engine bay! They rectified that, but then when I came to fit it, the return line clashed with the exhaust manifold so the turbo had to be removed and reindexed for the second time. So much for quality control! :)

It would not suprise me to find that the actuator has been set to the wrong pressure.

I've tested it with a mityvac and it take 0.5bar of pressure to begin opening. Maybe I'll adjust it to 0.4 and see if that makes any difference.

Not really an option (at the moment anyway) for me to take the turbo off yet again and send it back to them, or for me to drive all the way up to Yorkshire to see them in person.
 
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