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Wasted Spark Ignition System

Published on December 21st, 2023

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Explanation of a wasted spark ignition system.

Wasted Spark Ignition System

A wasted spark ignition system is a type of ignition system commonly used in internal combustion engines. It is designed to ignite the air-fuel mixture in the combustion chambers of the engine cylinders.

In a wasted spark ignition system, each cylinder has two spark plugs instead of the traditional one spark plug per cylinder. The spark plugs are positioned in such a way that one plug fires during the compression stroke (igniting the compressed air-fuel mixture), while the other plug fires during the exhaust stroke, when the spent gases are being expelled from the cylinder.

The name wasted spark comes from the fact that during the exhaust stroke, the spark plug firing does not contribute to the combustion process since there is no fresh mixture to ignite. Instead, it wastes the spark by igniting the residual gases in the exhaust. The primary spark plug, which fires during the compression stroke, is the one responsible for igniting the fresh air-fuel mixture.

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The wasted spark ignition system offers several advantages:

  • Simplicity: The system requires fewer components compared to a conventional single-spark ignition system, making it less complex and potentially more cost-effective.
  • Reduced ignition system complexity: With two spark plugs firing simultaneously, the system eliminates the need for a distributor or individual coil-on-plug arrangements for each spark plug. This simplifies the ignition system design.
  • Improved combustion stability: The dual spark plugs help ensure reliable ignition under various engine operating conditions, leading to improved combustion stability and reduced misfires.
  • Redundancy: In case one of the spark plugs or ignition systems fails, the engine can still operate on the remaining spark plug, ensuring a certain level of redundancy.

Wasted spark ignition systems are commonly found in many modern engines, particularly those with multiple cylinders, such as four-cylinder or six-cylinder engines. They provide reliable ignition and contribute to efficient engine operation.

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