Otto engine

technology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 21, 2026

Quick Summary

The Otto engine, often referred to as the Otto cycle, is a fundamental principle behind most modern automobile engines. It operates on a four-stroke cycle: intake, compression, power, and exhaust.123

During the intake stroke, a mixture of fuel vapor and air is drawn into the cylinder. This mixture is then compressed as the piston moves upward. Ignition by a spark plug initiates the power stroke, where expanding gases push the piston down. Finally, the exhaust stroke expels the spent combustion products.14

German engineer Nikolaus August Otto developed an engine based on this four-stroke principle in 1876, though the cycle itself was patented earlier by Alphonse Beau de Rochas. This engine provided a practical alternative to the steam engine.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

5 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

gasoline engine
Development of gasoline engines
) The four-stroke Otto engine was an immediate success. In spite of its great weight and poor economy, nearly 50,000 engines with a combined capacity of about 200,000 horsepower were sold in 17 years, followed by the rapid development of a wide variety of engines of the same…
Read More
) The four-stroke Otto engine was an immediate success. In spite of its great weight and poor economy, nearly 50,000 engines with a combined capacity of about 200,000 horsepower were sold in 17 years, followed by the rapid development of a wide variety of engines of the same…
Read More

Nikolaus Otto
…German engineer who developed the four-stroke internal-combustion engine, which offered the first practical alternative to the steam engine as a power source.
Read More
…German engineer who developed the four-stroke internal-combustion engine, which offered the first practical alternative to the steam engine as a power source.
Read More

combustion
In internal-combustion engines
The Otto engine operates with a mixture compressed in a cylinder by a piston. Shortly before the piston reaches the top the mixture is ignited with a spark, and the flame propagates at a normal velocity into the unburned mixture, increasing the pressure and moving the…
Read More
The Otto engine operates with a mixture compressed in a cylinder by a piston. Shortly before the piston reaches the top the mixture is ignited with a spark, and the flame propagates at a normal velocity into the unburned mixture, increasing the pressure and moving the…
Read More