G28 engine speed sensor for AAN conversion

[twoqu]

I agree that the TDC mark on the flywheel could in fact be anywhere as long as as there was a corresponding reference point. Its annoying that its not particularly easy to see or have the facility to drop a bolt on pin into to take the guess work out.
This is furher complicated by the aperture in different gearboxes being in different places (016 for example) and that might be why TDC marks differ although the pin is in the same place.
The extra pins were used for some ancient diagnostic machine which used a similar sensor to the crank/engine speed one. It pushed into the hole in the bellhousing and either read TDC or someother variable.

[S2central.net]

You marked the position up wrong
It's not as far away as you think. The G4 is located virtually in line with the two holed bosses on the bell housing approx 40 degrees from the timing window.

I was out in the garage when you posted that - with palm in my face - here's my excuse. The engine is sitting vertical on a stand about 6ft from where I am working at the 'box so I picked the wrong hole in the bell housing for the G4 position.

As soon as I pinged the last post I went out to measure again and realised I had totally forgotten the tilt of the engine so I was indeed using the wrong window - T.W.A.T

New pics, diagrams and measurements to follow - still tricky to balance the G4 sensor on the flywheel mounted in position but it will be miles better than the last pics. D'oh !

[S2central.net]

OK - some sanity restored in this PDF attached with G4 pin sitting in the correct position. Summary is on last page where we can say the G4 pin travels approx 58 degrees past the sensor window until the TDC marks align. I still stand by the hexadecimal explanation as to why all the Audi docs are incorrect about this measurement - its a cool fluke more like, but now we have actual measurements.. and Dessie's timing light evidence with a VEMS application is pretty much bang on. I think we can put this one to bed now !

[UrS4boy]

The fly wheel bolts that you can see are the threaded ends which screw into the crankshaft. Look at the photo as if you are the crankshaft - turning clockwise, with the reference marks at approx 1 o'clock and the G4 sensor window at approx 4 o'clock..

Then how do you know that you have the clutch/flywheel combo properly "timed"? You could be one spline out. 1/26 = 13.5 degrees

From the photo you have posted, I don't think that "0" (TDC) is in the middle of the viewing window as per spec.

If you measure from the TDC mark to the CENTRE of the G4 timing pin, how many degrees is it? More than 98. Maybe 102?

[S2central.net]

No need to bring clutch alignment into this Dave - thats an irrelevance. I lined up the TDC marks 100% with the flywheel in the bell housing - the spec is less about using the centre of the window but lining up the flywheel mark with the edge of the casting in that window. The 98 versus 102 degrees is easily explained...

If you count teeth from centre of G4 lug round to TDC mark you get 38.25 teeth which is 102 degrees

If you count teeth from the first +ve edge after an imaginary counter resets after the passing of G4 that yields 36.75 teeth which is 98 degrees (or 62 in hex !)

[UrS4boy]

I lined up the TDC marks 100% with the flywheel in the bell housing - the spec is less about using the centre of the window but lining up the flywheel mark with the edge of the casting in that window.

If you count teeth from the first +ve edge after an imaginary counter resets after the passing of G4 that yields 36.75 teeth which is 98 degrees (or 62 in hex !)

The photo doesn't show that. It appears to be "off". Have to take your word on it. (I have spare engine but not a loose spare trans).

You are obsessed about the 98 = 62 in hexidecimal thing. I am guessing that it is a red herring and just a coincidence. Nothing more.

[A1QSHIP]

Um, Could the measurement not be made from the leading edge of the timing pin rather than the trailing edge? I believe that the trigger could be set from either leading(rising) or trailing(falling) edge of the sensor. How does that change your measurements?

[S2central.net]

The photo doesn't show that. It appears to be "off". Have to take your word on it. (I have spare engine but not a loose spare trans).

You are obsessed about the 98 = 62 in hexidecimal thing. I am guessing that it is a red herring and just a coincidence. Nothing more.

Did you look at the last PDF I posted in the thread Dave ?
Page 3 shows the alignment pretty well - obviously i cannot push the flywheel far enough back that every sits as it would on a running engine, but that doesn't change the geometry.

I fully appreciate the 62 degrees in HEX started as pure comedy, but it works if you start counting teeth after G4 has passed !

What we can be absolutely certain of is the the factory docs are wrong about 62 degrees between the G4 pin and the TDC mark... Its clearly 102 degrees if you go by centre of G4.

[UrS4boy]

Did you look at the last PDF I posted in the thread Dave ?
Page 3 shows the alignment pretty well - obviously i cannot push the flywheel far enough back that every sits as it would on a running engine, but that doesn't change the geometry...What we can be absolutely certain of is the the factory docs are wrong about 62 degrees between the G4 pin and the TDC mark... Its clearly 102 degrees if you go by centre of G4.

I did see that but it might not have sunk in. Now it has. I have even posted a photo in my clutch slave post that would have shown that same "tab" BUT I didn't see it and I therefore didn't label it. In fact one of the label arrows goes OVER it.

102 degs is what I said in the beginning based on me counting teeth on a NIB AAN DMFW.

REFERENCE: Reason why fluid(s) might their way into the 01E transmission bell housing:

http://forums.quattroworld.com/s4s6/msgs/291460.phtml