dist. hall signal, 62 degrees BTDC too (like crank)? [was: Re: 034 EFI]

[Orin Eman]

> Below it says that the "distributor" hall sensor signal for Cyl 1
> (compression) TDC is 62 degrees BTDC.
>
> We determined that the "crank" timing reference pin is located 62
> degrees BTDC.  But until re-reading this post below, I was under
> the impression that the "distributor" signal occurs at 0 degrees
> TDC for cylinder 1 at the compression stroke.
>
> So, either the distributor hall sensor sends its signal 62 BTDC or at
> TDC, relative to no.1 compression stroke.  Which is it?

The hall sensor window is _centered_ on 62 deg BTDC.  The engine won't
start if the timing pin signal doesn't occur during the hall sensor window.

> I also read that the duration or window size for the distributor hall
> signal is 40 degrees for the 20v 3B motors.  Is this spec the same
> for the MAC11/MC-1's?

The measurement I made was 5 deg on a 4 cyl dwell meter (ie 5 out of 90 deg.).
That translates to 20 cam or 40 crank degrees.

> It would make sense, since it's probably the number of cylinders
> that determines this spec, it's either facing the right
> "neighborhood", or not, when the no.1 cylinder is at TDC (either
> compression or exhaust strokes).

Things become clearer when you realise that TDC on any cylinder _isn't_
particularly interesting or useful.  Everything of interest concerned with
firing a particular cylinder occurs _before_ TDC.  In fact the MAC11 ECU
has no concept of TDC.  Everything is based off the 62 deg BTDC reference.
Knock windows (when the ECU listens for knock) are after TDC, though I
don't recall the exact numbers.

BTW the timing pin is at 60 BTDC on the UrQ as was mentioned in another message.

Orin.