How does a Waste-Spark Distributorless Ignition System (DIS) operate?

How does a Waste-Spark Distributorless Ignition System (DIS) operate?

• A. All coils fire sequentially
• B. One coil fires two spark plugs at the same time when one cylinder is on the compression stroke, and the other cylinder is on the exhaust stroke
• C. Each coil fires only one spark plug
• D. The coils all fire at the same time

Answer: (B)

In a waste-spark distributorless ignition system, a single ignition coil fires two spark plugs at the same moment. When one cylinder is on the compression stroke and needs a spark, its plug fires; at the same time, the paired cylinder is on the exhaust stroke, so its spark is wasted and doesn’t ignite anything. This arrangement uses fewer coils than a coil-per-plug setup and is controlled by engine sensors rather than a distributor. The description matches the idea of one coil serving two plugs, one for the compression stroke and the other on the exhaust stroke.

In a waste-spark distributorless ignition system, a single ignition coil fires two spark plugs at the same moment. When one cylinder is on the compression stroke and needs a spark, its plug fires; at the same time, the paired cylinder is on the exhaust stroke, so its spark is wasted and doesn’t ignite anything. This arrangement uses fewer coils than a coil-per-plug setup and is controlled by engine sensors rather than a distributor. The description matches the idea of one coil serving two plugs, one for the compression stroke and the other on the exhaust stroke.