Two-Stroke Engine

An internal-combustion engine that has one power stroke per revolution.

Animation of a two-stroke glow plug engine.

The sequence of events is:



Compression Ignition

The two-stroke Compression Ignition engine does not suffer from the disadvantages of the spark ignition engine which are fuel loss and idling difficulty and hence CI engine is more suitable for two-stroke operation.


The two-stroke spark ignition engine runs irregularly at idle and may even stop at low speeds when mean effect pressure is reduced to about 2bar.

Schnuerle Ports

The inlet ports are placed on both sides of the exhaust ports so that the incoming air enters in two streams uniting on the cylinder wall opposite the exhaust ports, flows upwards, turns under the cylinder head, then flows downwards the other side to the exhaust ports. Such a system of air deflection reduces the possibilities of short-circuiting to minimum.

Spark Ignition

The two-stroke SI engine suffers from two big disadvantages-fuel loss and idling difficulty.


"Theory and Design of Automotive Engines", B Dinesh Prabhu, Assistant Professor, P E S College of Engineering, Mandya, KARNATAKA

See also: Engine, Four-Stroke Engine, Petrol Engine.

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Subjects: Automotive Engines