| The burning of the air/fuel mixture. | |
| A signal that varies the ratio of on-time to off-time, resulting in a square wave that can range between zero and 100; in a process, the ratio of on-time to total cycle time; in fuel injectors, the percentage on-time to total cycle time; in solenoids, the percentage of on-time to total cycle time. | |
| Anti-lock brake system | |
| A distributionless ignition system in which spark distribution is controlled by the computer. |