Where happened to distributors?
For most of the existence of the automobile, the primary method of providing spark in an engine were distributors, a device that distributed (duh) electrical current to the spark plugs via a rotating central hub with wires. Sparks, as one should know, are shot into the piston chamber to ignite the air and fuel mixture, which drives the engine. Today, ignition coils – or put more accurately, coil-on-plug ignition coils – are now the standard.
Older systems required a magneto (a type of electromagnet) to provide ignition. One engaged it by winding a crank, which created an electrical current that went to an ignition coil and started the car once sufficient current was attained.
Anyhow, there’s a good reason for it.
The term “ignition coil” can be misleading; ignition systems which employ distributors actually have an ignition coil. Back on point, the plug’s acutal spark is “timed” via mechanical movement rather than by computer. The way it works is like so:
The distributor itself is rotated via the engine’s crankshaft. Inside the distributor cap – where the points protrude from – is a rotating shaft with an electrical terminal, called the “rotor.” Current is supplied by an ignition coil, an induction coil that receives current from the battery, amplifies it, and sends it to the distributor and the rotor.
Under the cap are a number of terminals, which connect to the points on the top of the cap. As the rotor spins, it makes contact with the point terminals. This completes a circuit, which sends current from the point, through the wire, to the spark plug and combusts the air/fuel mix.
Coil the rod
In terms of machines, distributors are actually pretty simple. A rotating terminal spins, making a number of contacts and completing very small circuits. However, even the simplest things can be improved upon.
The drawback of any mechanical system is that it is mechanical. More moving parts means that they eventually stop working as well. Electronic ignition systems were developed over several decades. As computer-controlled systems became the norm, increasingly precise and efficient systems came into being. Why, then, trust a mechanical component when the spark can be computer controlled? They’re less apt to go wrong. Just like carburetors vs. injectors, the latter option was easier to control, more efficient and just did the job better overall.
Today’s coil ignition is controlled either by coils mounted in the engine bay which send spark to the plugs via wire – not too different from a distributor system – or by coil-over-plug coil packs. Either method’s timing is computer-controlled.
The latter are a small induction coil that fits directly over the plug via a sleeve. Imagine an upside-down beer coozy with a wire and you aren’t far off. They’re relatively cheap (compared to, say, buying your own island, in some cases…he bitterly grumbled) and easy to replace.