Why does a TEC TD80u have 3 pickups? (CIVIC)

kind of off topic...
I have a TEC TD80u here on my desk. It has 3 pickup coils in it, I was hoping someone could break down the function of each for me

the top pickup coil faces a rotor with a single lobe on it. I assume this is some kind of top dead center reference

the middle one faces a 24 tooth wheel.

the bottom one faces a four lobe one like the one in the 3gee TD42K, however it does not hook up to the ignitor

the wires all leave the dizzy, I guess to the ecu. Why does it need 3 sensors when 1 can do the job of all 3? If they cut one of the 24 teeth off that could be used as a TDC and a reference sensor eliminating the need for the others

it'll be no differant to any other tec dist.
1 for tdc number 1
4 for the cylinder position
24 for crank angle in 15 degree increments

The single tooth sensor tells the computer which half of the engine cycle the crank is on. It takes two revolutions of the crank to complete a full cycle (fire all four cylinders) so the computer needs to know whether it's on the 1-3 half or the 4-2 half.

The 4 tooth (as I recall) is the TDC marker for each cylinder.

Technically the computer could use just the 1 tooth and 4 tooth signals to control the injector and ignition timing, but the 4 tooth signals are so far apart that the information wouldn't be very accurate. So they add a 24 tooth signal to provide higher timing resolution.


C|

Cool thanks