Spark-ignition (petrol) engine basics In a conventional petrol (spark-ignition) engine, the combustible air–fuel charge inside the cylinder is initiated by an electric discharge produced by the spark plug. Is this statement correct?

Introduction / Context:Petrol engines are also called spark-ignition (SI) engines because combustion is started by an electrical spark. Recognizing how ignition is initiated is fundamental for understanding timing, knock control, and the differences between SI and compression-ignition (diesel) engines.

Given Data / Assumptions:

• Engine uses a premixed homogeneous air–fuel charge (gasoline/petrol).
• A spark plug is installed in the combustion chamber.
• Normal operating conditions without abnormal misfire.

Concept / Approach:

In SI engines, the ignition system (coil, plug, and controls) creates a high-voltage pulse that jumps the spark plug gap at a precisely chosen crank angle. The spark kernel grows into a flame front that propagates through the mixture. This is distinct from diesel engines, where fuel auto-ignites due to high temperature from compression and no spark plug is required for normal operation.

Step-by-Step Solution:

Verification / Alternative check:

Workshop manuals and engine wiring diagrams always include a spark plug in gasoline engines; diagnostic trouble codes for misfire often relate to ignition components, confirming the essential role of the spark plug.

Why Other Options Are Wrong:

Limiting ignition to two-stroke, cold start, or high speed is incorrect; sparks are required throughout operation at virtually all loads and speeds in SI engines.

Common Pitfalls:

Confusing glow plugs (used in some diesels for cold starts) with spark plugs; glow plugs do not provide a spark and are not used in petrol engines.

Final Answer:

Yes