DME CASIS question
 

I was just entertaining myself looking at Wilke's 84-88 DME schematic again.

It looks like the CASIS light drive comes off the injector driver (unknown custom part). The only input to the driver is a discrete from the micro controller, I assume being an injector on - off signal. So how does it work?

Is the injector pulse width modulation synchronized with engine rpm?

It seems like my light works as follows:
Annoyingly low RPM part throttle it comes on.
Wide open throttle some RPM it comes on.
Take your foot off the gas in overrun it goes off.

Does just the injector duty cycle have all this info in it? I'd ask this on diy-efi but it's been down for months.

Here's another data point, maybe it's helpful:
The CASIS light also doubles as the Rev Limit light.
Interestingly, even after you disable the CASIS light by disconnecting the black (?) wire on the back of the tach, the light will still come on when you hit the rev limit.
I was looking at this circuit a while back. When I discovered it wasn't useful for my (evil) purposes I ceased my investigations.
-Chris

The light you mention is the up-shift indicator and comes "on"
when injection duty cycle reaches a preset value. This value
is computed by the uP in the tach based on the DME output
on pin 11.

Have Fun
Loren
'88 3.2

It seems to be dependent on more than just one thing because it does depend on throttle and rpms. Yes, if you are light in the throttle it will come on ridiculously early (for gov't emissions reasons, especially when it directly contradicts the minimum shift points in the owner's manual), if you are heavier on the throttle it will come on later, if you let off of the throttle it will go off (the computer shuts fuel off from the engine if the throttle is closed and you are over 1800 rpm), and it also comes on at redline.

All those things affect the injection duty cycle! Put a scope on pin 11
and see what happens for yourself. It's basically same as what you
see on each injector w/o the inductive ringing.

Have fun
Loren
'88 3.2