[s-cars] No Start ABY/AAN engine - Problem Found?

[Ben Swann]

Scott,
 
I take having the pin a little farther out would also give better signal resolution -
how much room for error before it interferes with the sensor in a bad way?
 
I am contemplating a few things:
 
1. Drill existing hole as dead on as possible.  Install a slightly larger diameter pin
than - 3mm is IMO kind of small.  I rounded up some nice metal stock from my
grandfathers collecion of machinists parts and supplies he left us.  I have pins ranging
from below 3mm to 13mm.  I was considering around 5mm.   This is about as hard of steel
as can be had, yet still be magnetic.
 
2. Your comments suggest I can drill toward the outside of the flyheel - just outside
the pin where I will find drilling easier.  It would make sense to do this and use a pin
that leaves just a small amount of clearance - and/or I could even shim the sensor out a
little farther too.  I could even machine the larger pin located farther out and take
off a sector to compensate - so that the flat side is facing the sensor.
 
3.  Make a tab that is essentially the same as the one for the AAN flywheel and drill a
hole father in toward the center to position the tab.  Tack weld the tab in to
positively secure it.
 
4.  offset any additional mass of the new pin or tab by either adding a second pin 180
deg. out or drill enough material near the new pin to offset the added mass.  By added
mass I mean the amount of mass difference between the original pin and the newer pin.
Or am I worrying too much about a gram or less of additional mass?
 
Of course I'll rotate and fit check everything before committing with red-locktite.
 
Thanks for all the help and suggestions.  I'm still refining what I'll do and plan to
consider any and all suggestions before starting to drill in the AM - starter coming out
this eve.  
 
Ben


  _____  

From: qshipq at aol.com [mailto:qshipq at aol.com] 
Sent: Monday, October 04, 2010 2:40 PM
To: benswann at verizon.net; cody at 5000tq.com
Cc: jc at j2c3.com; s-car-list at audifans.com; chris.miller at bqconsultants.com
Subject: Re: [s-cars] No Start ABY/AAN engine - Problem Found?


Thank you!  And you then don't need these pics of the 3B flywheel I did up for you,
maybe it will help others understand the concept...  
PP side:
http://forums.audiworld.com/picture.php?albumid=162452&pictureid=226928
Block side:
http://forums.audiworld.com/picture.php?albumid=162452&pictureid=226929

FYI, the wider pin block from the AAN is not available as a separate part AFAIK.  I
purposely did not put 3mm pin dimension as Cody notes the 3B comes from the factory, as
it's not a critical dimension.  It's critical in tooth-from-TDC placement, and in
clearance to the sensor only.  I labeled it as "min" dimensions and in fact, you can go
as wide as the AAN pin block on either an AAN or earlier (3B/MC flat or dished) FW.
IME, a wide pin top-shaved a bit longer than 11mm (= as long as it clears the block in a
revolution) will give the strongest wave signal off the timing reference pin.  In a
couple cases where I've had to 'redo' someone elses work, I have redrilled above the
stock pin location, and just shimmed out the reference sensor for proper clearance.

HTH

Scott J


-----Original Message-----
From: Ben Swann <benswann at verizon.net>
To: qshipq at aol.com; cody at 5000tq.com
Cc: jc at j2c3.com; s-car-list at audifans.com; chris.miller at bqconsultants.com
Sent: Mon, Oct 4, 2010 9:50 am
Subject: RE: [s-cars] No Start ABY/AAN engine - Problem Found?


Well - son of a gun!
 
I just checked the two 3B flywheels that I had spare.  Neither of them have a pin
protruding backside, but there is a nub where one should be.  I don't recall there being
one on the one I installed, so this must be the problem.  Also, the flywheel I pulled
off the AAN has no such pin.  but does have a large tab mounted where the pin would be
on the 3B one.  There are also two tabs located like the pins clutch side on the AAN -
that is where I confused them for the sensor pins.
 
So it appears there was no change in location of the pin with respect to the ECU
programming, just that my pin is missing.
 
Now it all makes sense.  Wish I'd checked this before installing.  I am certain I can
make this repair in situ.  The pin is easy to locate and I'm pretty good at drilling
holes in tight spots even if it is hardened metal.  This is certainly a lot easier the
removing the trans and I'd have to drill the hole anyway.
 
I had been under the impression that the two pins protruding from the front were the
sensor pins - especially since the timing diagrams show two spikes that correspond to
those pins.  However, the timing diagram is for Ur Quattro not the newer engines.
 
I'm wondering if I should install a tab similar to the AAN flywheel instead of a pin -
it appears to be a centimeter square peice of steel that is located by two pins - one
pin is where the pin would be and the other just below that.  I wonder if this is a
dealer item.
 
Thanks Cody and Scott for catching this!
 
Ben