A magneto ignition system is essentially the same as a battery system except that a permanent magnet generator supplies current directly. Where compactness is an advantage or where there are no other accessories that require a battery, a magneto system may be preferred. Aircraft, motorcycles, and farm equipment often have magnetos.
In a diesel engine the fuel ignites as soon as it is injected into the hot, highly compressed air in the cylinder. Diesel engines frequently utilize an electric heating element, called a glow plug, inside the cylinder to preheat the air to facilitate starting and running until the engine has reached its operating temperature.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.