80 SC Distributer question

What is the purpose of electrical plug that goes to the distributer? I know my distributer has two vacume lines, one for advance and one for retard, so it can't be a timing part. Anyone know?

I'm gonna take a wild guess with the hope you are not insulted. Hopefully I will just embarrass myself.

Power (12v) typically goes to the coil, then to the distributor, then back to the coil again. That's the low voltage side (non-huge, non-ignition wires).

So you see, the 'points' need to pass electricity, which I believe builds up in the condenser and is amplified by the coil. (Boy am I talking about something I do not understand) And of course, you car has no points so things may be different.

Warre, please enlighten us.

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'83 SC

The two-pin connector coming out of the distributor is from a stationary pick-up coil that triggers the CDI-unit in place of the points. The CDI-unit is not 'smart' and has no controller or processor. Hence, the timing control work and 'advance curve' still has to be done by the distributor. In place of a cam is a notched magnetic wheel, the control of which is done by a combination of a centrifugal advance mechanism, and a vacuum advance/retard diaphram. The magnetic wheel turns at the same rate as the engine camshaft, once for every two rotations of the crankshaft, and the advance or retard is done in relationship to the timing cycle of the cams, though usually shown in terms of a 720 degree diagram for the crankshaft!

The CDI-unit has an amplifier to boost the signal from the pick-up coil (in the distributor) and pulse-shaping circuitry to determine when to trigger a 350-400 V. pulse to the coil, called an ignition transformer in the description of the CDI-system. The CDI-unit also has a special oscillator called a DC-to-DC converter, which charges up a large capacitor to 400 Volts, from which the Voltage for the trigger pulses to the coil is obtained.

The signal from the pick-up mcoil is very small, typically 0.5 V. in amplitude, and is sent to the CDI-unit over a shielded cable, usually called coax in the electronics industry, to prevent interference, such as from the sparkplug leads.

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 08-11-2000).]

You sure know a lot of stuff, Warren. Thanx for checking in on us from time to time.

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'83 SC