ABY ECU Intermittent issue

[twoqu]

Thats the trouble with gauges. If you don't have one you are blissfully ignorant of whats going on and if you do have one you constantly wonder if everying is all right!
Having said that it is a useful addition even just from a diagnostic point of view. You need to know whats going on in the boost department.
Hopefully you should be in the stock drivability mode so the vehicle should be reasonably civilized!

[edge_devil]

Here is what Uncle Dave has to say on the matter:
http://forums.quattroworld.com/s4s6/msgs/22584.phtml

He does write some good stuff doesn't he

[edge_devil]

Disconnected MFTS still only 0.5.... THEN...I realised I need to put my foot down to get full boost so it may not be the MFTS, just me taking it easy.

I now get a good solid build up to about 1bar that stays there until I let off, as opposed to a massive thump in the back, boost to 1.5 and at 4000 rpm it's all gone, which on it's own was a lot quicker but a lot less reliable or easy to drive.

I have had a few momentary 'coughs' from the ECU that I need to check out, I'm not sure if everything dies as in power failure, or if its a G68 failure for example, but one step at a time, the turbo and wastegate seems to be working well at last, not least thanks to your collective assistance

Now debating if I take the risk to drive to a customer meeting in Milton Keynes tomorrow morning to give it a good shake down.....

[twoqu]

Here is what Uncle Dave has to say on the matter:

http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[twoqu]

Part of the problem is that we don't really know what you have done in terms of wiring and plumbing!
I was only trying to give some information that might be useful IF you have the MFTS connected up and the overheat signal goes back to the ecu. If you don't then its not the cause.
However we know that on S2 models, the MFTS can give either a faulty or genuine overheat signal which will cause the ecu to stop activating the wgfv to give the basic i.e safer mechanical boost limit of 0.4bar. This function does not appear on S4/S6 models. Not sure whether its in the SW or not.
The MFTS provides the temp gauge signal and 2 overheat signals in the S2. This is not the sensor in the rear of the head as that is just for the Motronic. Normally its easier to just disconnect the MFTS to prove/disprove a problem as its easier to access for us. The same of course might not be true for you. Can't see thats it its necessarily a good idea to keep opening the ecu up.

[edge_devil]

Your logic is sound

...so the temp sender on the back of the head is the only one used...but is the MFTS only used for the dash?

I'm using my separate dash and temp sender so if that's all no issue!

[twoqu]

But that circumvents the idea of trouble shooting in a stock config! Of course its up to you. Its safer to use stock until you are certain everything is as it should be. I guess you are only using the MFTS for the ecu anyway so if its faulty you can just leave it disconnected if the theory holds up.

[edge_devil]

ABY ECU Intermittent issue

Just thinks btw, I can try the mfts, but also I can drop the Nero chips back in and see if they develop more boost as they are adu code and not reliant on the mfts...

Glad I made the ecu more accessible!


Sent from my iPad using Tapatalk

[edge_devil]

We've now got stock ABY code in thanks to you Robin, but I can try the MFTS as you say.

Still no fault codes from the box, just checked... the hunt continues!

[twoqu]

Should be nearer 1bar!
Best to check for codes though first just in case. If no codes are shown and you are only getting that level of boost its possible if you are on ABY SW that the MFTS has an overheat signal which limits boost but does not throw a code. The SW is important as on the AAN this function is not used. I think we ID the modified SW as AAN based due to the 4A0 ID.
If you have the MFTS connected up (the large brass thing in the water rail on the cylinder head) you can try and disconnect it and see if full boost is restored.

[edge_devil]

Yay, idiot removed from the equation......

With N75 disconnected I am now getting a reliable .04-0.45 of boost, so that is a big Plus. I drove out with the N75 disconnected, stopped, reconnected it, switched off the battery for a minute and then drove back. This still only went to 0.4-0.5 boost, what would I expect from a normal engine?

I'll do the tests later that let the ECU switch the N75 on/off so I can confirm that is working, but I had done that a week or two back so I'm expecting that is all fine.

[edge_devil]

Hi my name is Tim and I'm a village idiot....its been two days since I did something really stoopid!!!



...yep that's the nipple with nuffing on it! Now fixed and I removed the N75 and connected it back up according to the diagrams. Hopefully a quick run at lunch time with the N75 disconnected from the ecu I should see a difference!

Sent from my Nexus 5 using Tapatalk

[edge_devil]

Sorry don't have my laptop to hand to label the picture....but all clear which goes where....now to test!!! ...and I'll provide a labelled diagram later, but photos of the new setup may be harder as the bodyshell is now on


Sent from my iPad using Tapatalk

[twoqu]

Nope!
The long one on the side goes into what we would call the MAF to turbo hose which essentially is vacuum. On the OE hose it is pushed into a small bore opening which of course you don't have.
The one opposite it goes to the lower port of the wastegate.
The one on the bottom goes usually to the nipple fitting on the turbo compressor which is essentially pressure.
Dave has provided a link with enough information to allow ID and orientation.

[UrS4boy]

...We are basically trying to find anything that isn't as it should be in a factory install.

Agree. An unlabeled photo of a Medusa-head of purple hoses doesn't help us to help Mr. Devil.