Pre-ignition is defined as combustion taking place where?

Pre-ignition is defined as combustion taking place where?

• A. At normal spark timing
• B. Within cylinder before the timed spark jumps across the spark plug terminals
• C. After piston top dead center
• D. During exhaust stroke

Answer: (D)

Pre-ignition means the air–fuel mixture begins burning inside the cylinder before the timed ignition spark fires. This premature ignition is caused by hot spots in the combustion chamber—such as a hot piston crown or carbon deposits on the plug—that ignite the mixture during the compression stroke before the spark event would normally occur. It is not the normal ignition timing, and it does not happen during the exhaust stroke or after top dead center as part of the intended cycle. So, the combustion is already underway in the cylinder prior to the spark being triggered.

Pre-ignition means the air–fuel mixture begins burning inside the cylinder before the timed ignition spark fires. This premature ignition is caused by hot spots in the combustion chamber—such as a hot piston crown or carbon deposits on the plug—that ignite the mixture during the compression stroke before the spark event would normally occur. It is not the normal ignition timing, and it does not happen during the exhaust stroke or after top dead center as part of the intended cycle. So, the combustion is already underway in the cylinder prior to the spark being triggered.