MFTS Do ABY/ADU use it ??

[r1alex]

3 pin 0r 4 pin on an aby

ok if the motronic ecu pin 46 must have a 2 volt+ signal to enable full boost , how does it get this from the 3 pin sender, which has no 12v input.
The reason i ask is because my aby avant is fitted with a 3 pin sensor, should it have a 4 pin sensor, I toyed around with the idea of sending a 2volt signal down this wire with a battery, then read a warning in the manual not to do this , this mfts thing is really confusing me .
IF all that is stopping full boost is this sensor i would indeed be a happy man, and I would have been right for once, a rare occurnce indeed.

[UrS4boy]

The ABY and ADU are very easy - they make use of the R pin from MFTS which enters the ECU at pin 46. There is a specific test procedure defined for it in the ABY Motronic book.

The fact that its NOT supported on the AAN is the anomoly here. MB, MC, 1B, RR, 3B, ABY and ADU all seem to support it. Zut alors !

It is very interesting that the AAN does not use the MFTS via pin 46. In the evolution of the engines, the AAN fits between the 3B and the ABY, i.e. the AAN came out in the 92 MY S4, before the switch from the 3B in the S2 to the ABY. It could be that the factory decided that having a MFTS switch input to the ECU was a good thing after all. However, if that was true, you would think that the later e.g. 94 to 97 My S4s and S6s, would have a MFTS input, but they don't.

[r1alex]

does no one Know how a 3pin mfts sends a signal to the ecu?

[UrS4boy]

Cell phone. Couldn't get a hard line so they set up a cell network and phone the signal in.:mischeif:

The good news its still analogue.

[r1alex]

well thats just dandy usrboy.

[S2central.net]

Guys - I'm going to try and buzz this out on my car.

[r1alex]

s2 thankyou, please see if your car is fitted with a 3 or 4 pin, as if athree pin is fitted,how does it send a signal to pin 46 of 2v or more.

[S2central.net]

Think I have the four pin actually...

The voltage derived for the 'R' pin might come from the ECU remember - not necessarily thru the 12V source on the 4-pin MFTS. A thermistor on the R pin could be part of a potential divider network which changes the voltage at the R pin when temperature is high.

I'm at home this week and will try to get to the bottom of this !

Would be a real PITA if the 3-pin MFTS didn't work properly on the engines which require it... And I'm totally flummoxed as to why Audi chose not to use it for this on the AAN motor.

Paul

[merlin's S4]

Oops **Deleted!!**

[S2central.net]

OK - I have some results from a lil early morning test session.

All of the MFTS wiring goes thru one of the cylindrical loom connectors on the bulkhead - T8f for the ABY. Thats the one with 8 pins fitted... Not to be confused with T8e which has 6 pins fitted. Top portion of T8f connects to the MFTS - bottom portion (pins) goes to the car.

I disconnected the plug at T8f and verified the following -

MFTS Pin 1 = T via T8f pin 6 is brown/blue. I measured 1387ohms to 0V at ambient

MFTS Pin 2 = R via T8f pin 5 is blue/white. This is the alarm signal sent to ECU when temps are too high so that boost can be reduced. I measured 0V coming from the sensor side (as expected). I measured infinite resistance to 0V on the sensor side (as expected) and verified that +5V was present on the ECU side of this pin. Verified this ONLY exists when the ECU was plugged in. It would appear that the behaviour of the R pin is to short to 0V (bit like the C pin) when temp is too high.

MFTS Pin 3 = 12V. Verified this available with key ON. Its a black/blue wire on T8f / 8

MFTS Pin 4 = C. This is open circuit (as expected) on the sensor side and connects to T8f/3 with a blue/yellow wire.

So in summary - it doesn't matter if you have 3-pin or 4-pin MFTS and what ECU you use. The ECU will pull this pin up to 5V internally and only when its grounded will the ECU activate the boost reduction (unless its AAN software which *might* be programmed to ignore this pin).

Faw what an episode...

[ifa]

ABY goes to 0.4-0.6 bar. "mechanical boost" if the ecu sees overheat signal from MFTS.

[S2central.net]

Yes - thats what I've been saying... It effectively turns off the WGFV when this overheat signal is active. I might just try to force this condition to see it for myself.

Paul

[r1alex]

thanks paul,
after pm with you the other week, i replaced the wgfv, this did'nt seem to make any difference to my wastegate controlled boost, so after messing about I unplugged the mtfs and took it up the road and noticed a difference, but it was the coldest night of the week and I was indeed driving like someone who had lost the plot.
I also did'nt really want to post a thread stating that I thought the general consensus about aby mtfs usage was incorrect for fear of the type of unhelpful comment posted by us4r.
Anyway the thing that was confused me was that the pin out i read listed pin 46 as an input, which in my small mind ment voltage in to the ecu.
So as you say man with aby should look at his mfts if suffering from low boost as one of the many man reasons whe things don,t go as audi intended.
Paul thank you for spending the time.

[S2central.net]

I have updated some info at S2central in light of this little thread - while its fresh in my head -

http://s2central.net/cooling02.html

Note the 'Top Tip' section that I thought up tonight - it would be a nice tweak for failsafe operation.

Also - looked at 3B schematics tonight in English and they don't actually show the R pin connected to the ECU - despite the 3B self study book clearly stating that it connects to pin 36. I hate inconsistency like this...

Can some 3B owners PLEASE check the voltage on pin 5 of the T8f connector when the ECU is connected and the ignition is ON. Engine not required to be running.

I'll post a photo of T8f later today - its the one with 8 pins - they are all numbered.


Paul

[S2central.net]

Photo provided here from my ABY - 3B should be same in this regard. Just need someone to verify it with a voltmeter - its a 2 minute job really !