semidiesel

engineering

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Last updated

July 13, 2026

Quick Summary

A semidiesel engine is a type of internal-combustion engine, typically under 50 horsepower and often of the two-stroke cycle type. It shares similarities with a diesel engine but uses lower compression pressures, ranging from 100 to 350 pounds per square inch. Ignition is achieved by spraying fuel under pressure against a hot part of the combustion chamber or into a separate chamber that remains above the fuel's ignition temperature due to compression heat.1

Unlike a true diesel engine, which uses compressed air for fuel injection, a semidiesel engine might use other methods. These engines are generally less expensive to build and maintain than standard diesel engines.2

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diesel engine
Early work
…the development of the so-called semidiesel that operated on a two-stroke cycle at a lower compression pressure and made use of a hot bulb or tube to ignite the fuel charge. These changes resulted in an engine less expensive to build and maintain.
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…the development of the so-called semidiesel that operated on a two-stroke cycle at a lower compression pressure and made use of a hot bulb or tube to ignite the fuel charge. These changes resulted in an engine less expensive to build and maintain.
Read More