Otto Four-Stroke Engine

Heat engine · 1876 · Otto cycle

Year: 1876
Kind: Heat engine
Materials: Cast iron or aluminium block, forged steel crankshaft, aluminium pistons, platinum and rhodium in the catalytic converter.
Efficiency: 25–35 % at best load; the ideal Otto cycle at r = 9 promises 58 %.
Used In: Cars, motorcycles, generators, lawnmowers — most of the engines on Earth.
Power Density: About 50–100 kW per litre of displacement in a modern car.
Cycle: Otto

How It Works

Intake draws in air and fuel; compression squeezes it to a ninth of its volume; a spark ignites it and the pressure drives the piston down; exhaust pushes the burnt gas out. Two revolutions per power stroke, and a flywheel to carry the engine through the other three.

Inventors

Nikolaus Otto

Equations

Ideal Gas Law Adiabatic Relation Thermal Efficiency Otto Cycle Efficiency Moment of Inertia Torque

Skills

Sand Casting

Elements

Iron Platinum Rhodium Aluminum

Referenced by

element

Aluminum Iron Platinum Rhodium

equation

Adiabatic Relation Ideal Gas Law Moment of Inertia Otto Cycle Efficiency Thermal Efficiency Torque

researcher

Nikolaus Otto

skill

Sand Casting

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From the Machines database in Notion, last edited 2026-08-18. This page is the row, rendered by the build; nothing on it is written by hand.