hall sensor on a '85 4kq? (5 window type?)

[Ken Keith]

Quoting JShadzi at aol.com:
>
> > Hi Javad!
> >
> > Meaning they both have some form of vacuum advance, but they are
> > different from each other?  Or, one of them has vacuum advance and the
> > other one doesn't.  If I were to guess (here I go), I would say the
> > 4kq has the vacuum advance, since I recall my past Coupe GT's as
> > having that little shift light that is affected by a functional vacuum
> > advance.
>
> Yes, the NG does not have vacuum advance, this is compensated for in the
> ingition control unit's maps.

So, if I don't want my hall signal to advance under vacuum, I should
disconnect the advance (see question below, regarding the effect of vacuum
advance on hall signal)?

> > Where do I tap into the hall signal?
>
> The middle wire in the hall connector.

Thanks, that's the question I was trying to ask.  Which wire, not so much
where along the correct wire.  Orin's answer was kinda funny to me, but is
still appreciated (tap into it wherever is best for the new ECU location).
:-D

> > Does the hall signal itself change with the vacuum advance, or is the
> > hall signal constant?
>
> The hall signal is only an electrical pulse when one of the windows
> pass.

I meant, is the timing of the hall signal affected by the vacuum
advance, or is it just the spark that's affected?  Here I am probably
really showing my ignorance.  I will physicaly look at my distributors
when I get home to see what I'm asking about.

> > I think I would still have to incorporate the timing reference pin in
> > the flywheel for my system to function correctly.
>
> Only for TDC if your system is valve-timed sequential.  If it is not,
> then you can easily pull your RPM signal from the 5 window hall, that is
> what I do on the 034 systems.  If it is, then all you need is another
> signal that pulses for TDC which can be done off the flywheel, cam gear,
> crank pulley.  You could use one of the existing hall sensors for the
> TDC signal.

Yes, the system and my intent is to run valve-timed sequential.  So
then, if I use the flywheel to give me TDC, I still need to also have
something off the cam to distinguish between which of the two TDC strokes
the piston is at?

I should be able to use the one window hall sensor on the MAC11.
That signal is TDC for cylinder 1, and only on the compression
stroke (or whatever is the best term for that).  But since that is cam-
driven, which I least prefer for my application, I also need to use the
timing reference pin in the flywheel to provide the accurate crank- timed
ignition signal (62 BTDC).

Here's an excerpt from a post that I think Orin made to the DIY-EFI
list:

<<Audi does this with their 5-cylinder motors.  They have a second
sensor and an index pin on the flywheel to identify TDC.  They also
use a hall- effect sensor on the distributor to give the 720 degree
info.>>

I'm really leaning towards trying to use all three points of reference for
my installation, if it's possible.  I since my system will be controlling
ignition too, and I intend to push things as far as possible (boost,
ignition timing, power, etc.), I don't want to have a system any "less"
safe than the stock Audi setup.

I will have to consult my tech support guy to ask him if that's an
option.

> > Someday in the future, I have the option of going with direct
> > ignition with 5 coils.  At that point, I don't need to use the
> > distributor for distributing spark.  But I guess I still have to
> > have one physically in the head to provide for the hall signal, if
> > that's where that stuff is.
>
> Unless you move your hall sender to the cam gear...

Right.

> > I think I may have to provide them the length of the flywheel teeth
> > and gaps.
>
> No you don't, see above...

That answer is only "no" if I'm not running sequential injection?

I can't tell if you mean I don't need the specs on the teeth
regardless of whether or not I am using them for rpm (I can use the
teeth for rpm but don't need the specs),

or if I only don't need the specs becasue I can use something
besides the teeth for rpm, like a cam mounted hall sensor (custom
on the gear, or a stock 5 window).

I hope that question was clear enough.

I would also like to know how many teeth are on the flywheel,
specifically for a 200tq flywheel.  Is it 135 teeth/pulses per
revolution, as Robert posted here?
http://www.audifans.com/archives/1995/08/msg00395.html
I'm thinking this may be different, since it was for an ur-q (the
location of the timing reference pin on that car is quoted as 60
degrees BTDC, not 62 like on the MAC11).

I want to use that excellent post to give to my tech support guy,
but since it has potentially confusing ur-q info in it, I won't (verbatim
at least).

Here's another post, from Dave, that says that there are 135 teeth.  I
suppose to be totally sure, I'll count the teeth on mine too.
http://www.audifans.com/archives/1996/05/msg01069.html

Is the single window hall sensor setup on the MC-1 the same as a
3B, in that it has a 40 degree window of magnetic field exposure,
as described on SJM's page here?:
http://www.sjmautotechnik.com/20vhall.html

I couldn't find a similar page for 10vt's.  Also, I can't get Chris
Miller's page to load today, there was some info there too.

Thanks for all the information!

Ken
'85 4kstq project, eventually using MC-1, LinkPlus efi/ems, 200tq
flywheel, KH manifold/TB, and? (plus non-engine mods)
other cars too