Vehicle ignition systems have developed considerably over the years to deliver improved, more reliable, and more powerful performance. Today, there are three primary ignition systems, and despite their differences in technology and components, they all work on the same basic principles.
The distributor automotive ignition system
A distributor-based automotive ignition system connects to the camshaft with gears. In the mechanical distributor, the gears spin the main distributor shaft. Inside, a set of “ignition points” rubs against a multi-sided cam on the distributor shaft. The cam opens and closes the points; they act like a mechanical switch that interrupts the current flow. That is what starts and stops the flow of power to the ignition coil. Once the coil generates firing voltage, it travels to the top of the coil and into the top of the distributor cap. A rotating disc attached to the distributor shaft “distributes” the power to each of the spark plug wires.
The distributor-less automotive ignition system (DIS)
This system determines spark timing based on two shaft position sensors and a computer. The Crankshaft Position Sensor (CKP) is mounted at the front of the crankshaft or near the flywheel on some vehicles, and the Camshaft Position Sensor (CMP) is mounted near the end of the camshaft. These sensors continually monitor both shafts’ positions and feed that information into a computer.
Coil-on-Plug Ignition System
The coil-on-plug (COP) vehicle ignition system incorporates all the electronic controls found in a DIS car ignition system. Instead of two cylinders sharing a single-coil, each COP coil services just one cylinder and has twice as much time to develop the maximum magnetic field. As a result, some COP car ignition systems generate 40,000 to 50,000 volts and much hotter, more vital sparks.
COP ignition systems have another significant advantage over DIS ignition systems. Since the coil mounts directly on top of the spark plug, spark plug cables are eliminated because the firing voltage is delivered directly to the pin. Plug cables mean more significant resistance loss of amperage and voltage, as well as the possibility of contamination and cross-firing between cables if they become greasy or worn.
Ignition systems will continue to improve with features that today are unimaginable as technology advancements lead to continued improvements. Even as they do, all three of these ignition system types are still well-suited to the vehicle era they were originally intended for and easy to maintain and repair.