90tq Turbo Conversion Timing Pin Placement

[Orin Eman]

> Well, my friend who was doing the timing pin for me ran into trouble and
> broke off a hardened steel pin in the correct location.  We were unable to
> remove it so I had him install another pin next to it, about 1.8° advanced
> of the correct position.

> see http://www.teenaflanner.com/chris/90tq_turbo_conversion_gallery/ for
> pictures of the goof-up
>
> My question is this:  what will this do to the engine operation?  I can't
> adjust for it by changing the distributor orientation, can I?
>
> There is something basic that I don't understand.  What does the computer
> use this signal from the flywheel pin for?  The distributor takes care of
> ignition and the injection is continuous, right?

The correct position of the pin is 62 degrees before TDC on cylinder 1.
Ignition timing relies on this and the flywheel teeth almost exclusively.
The hall sender signal from the distributor only serves to indicate
whether cylinder 1 is on the compression or exhaust stroke.
This pin must pass its sensor during the hall sensor window in
the distributor or the engine won't start.  Moving the distributor
can therefore result in a non-start condition.  The ECU also
relies on the hall sensor to reset its cylinder counter so if the timing
pin signal is out of the window at higher RPM, the ECU can lose track
of which cylinder is being fired... resulting in some incorrect tables
being used in detecting knock.  My guess is that this just causes
knock to be detected when it shouldn't, hurting performance.

If the pin is advanced, all your timing will be advanced.  The knock
sensor will save you in general, but you may get forced to the
regular fuel timing map which will cost in performance.

Orin.