hall sensor info found!

[auditude at get.net]

Hello,

In order to I get information to trigger a standalone engine
management system, I used a digital multimeter and took
measurements off the hall sensor while turning the crank by hand.
The car is an '88 5kcstq.

I was able to record the leading/falling edge location of the hall
sensor output window, as well as the trailing/rising edge.  The
window is 14 teeth apart.

I marked the tooth that was centered above the rpm sensor with
correction fluid at each location.

I then centered the timing reference pin above its sensor to see
where the marks were relative to that position.  Here is a pic.

http://photos.yahoo.com/bc/quattrophile/vwp?.dir=/EFI&.dnm=Image02-2.jpg&.src=ph&.view=t&.hires=t

I guess this tells me that the window is 37.33 degrees wide
( 360degrees/135teeth = 2.667degrees/tooth, 2.667degrees x
14teeth = 37.33 degrees total)

Orin Eman calculated the window at 40 degrees, using a 4 cylinder
dwell meter and mathematically converting into a 5 cylinder
number.  So, I feel that my number is within the ballpark and I'm
not doing or believing something totally wrong here.

The readings I got from the DMM were 4.63 volts when it is "high",
and 16 millivolts when it is "low".

The fact that the rpm sensor is not centered within the two white
marks in the pic is due to the variability of distributor indexing.
Since it is within the window, the car will run.

So, if the reference pin is located at 62 BTDC, and the distributor
can be centered, then I can split the window in half and get the
angle of the hall sensor output window relative to crank position.

If I split the window in half, 37.33/2=18.67, then I can add and
subtract those halves to the timing reference pin location and get
the numbers I need.  When I do that I get about 80.67btdc for the
leading/falling edge, and about 43.33btdc for the trailing/rising edge
of the hall sensor output.

I believe this may be enough information to get my efi ecu
configured to work with this trigger.

Since it's been so long anyways, another day might not make
much of a difference.  If anyone has any feedback for me on this,
please send it along.

Later,

Ken

p.s.  I had another idea, for those who might need a 5 window
trigger.  It looks like it might be possiblet to machine away 4
additional slots into the distributor in the right places, to convert the
single window hall sensor to a 5 window style.  Or, just swap out
the metal piece that seems to control the hall effect.  If I had
studied a 5 window distributor, I'd be able to say more about this.