Purpose of a Distributor in a 4-Stroke Petrol Engine

Distributors are ignition components.

A distributor is a component in the ignition system of a gasoline (petrol) engine and is used to route power from the engine's ignition coil to the spark plugs in the proper firing order.

Basic Desription

A distributor consists of a camshaft-driven rotor (rotating arm) housed inside of a distributor cap. When the metal tip of the rotor contacts the individual plug-wire contacts, the electrical circuit is closed and power shoots from the coil to the spark plug.

Timing Advance

Most distributors use a set of weights connected to the central shaft to vary timing advance relative to piston position. These weights are connected to the shaft with a spring and are forced outward under centrifugal force to turn the rotor.

Electrical Ignition

In the early 1970s, manufacturers began utilizing hall-effect magnetic sensors in place of old-fashioned mechanical "point" units to trigger the coil and control the length of its discharge time.

Disadvantages

The primary disadvantage of a distributor system is voltage drop through the rotor and limited RPM capability.

Direct Ignition

Modern engine designers have abandoned the mechanical distributor in favor of fully electronic direct ignition systems. These systems use magnetic sensors and spark plug-mounted coils to eliminate the inherent weaknesses of a distributor system.

References

• CarCraft: Installing a Distributor - How To Stab A Distributor
• Mopar Muscle Magazine: Installing A Hemi D.U.I Distributor

Resources

• Replacing a Distributor Cap