CPT Ignition Systems & Timing 2

Question 1

What is dwell angle in a conventional points-type ignition system?

Accepted Answer

The number of degrees the distributor cam rotates while the points remain closed

Answer

Dwell angle is the number of degrees the distributor cam rotates while the contact points remain closed, allowing the ignition coil's primary circuit to build magnetic field energy before firing.

Question 2

What advantage does a coil-on-plug (COP) ignition system offer over a conventional single-coil system?

Accepted Answer

Each cylinder gets a dedicated coil, providing maximum energy and faster recharge time

Answer

Coil-on-plug systems dedicate one ignition coil per cylinder, allowing each coil maximum saturation time independent of engine speed and delivering higher, more consistent spark energy.

Question 3

What is the primary role of a crankshaft position sensor (CKP) in a modern ignition system?

Accepted Answer

To provide the ECU with engine speed and piston position data for spark timing

Answer

The crankshaft position sensor sends a signal indicating the exact rotational position and speed of the crankshaft, which the ECU uses to calculate precise ignition timing for each cylinder.

Question 4

How does pre-ignition differ from detonation?

Accepted Answer

Pre-ignition occurs before the spark fires; detonation occurs after the spark fires

Answer

Pre-ignition is caused by a hot spot (such as a glowing carbon deposit) igniting the mixture before the spark plug fires, while detonation is the spontaneous ignition of the end-gas charge after the spark has already fired.

Question 5

How does higher altitude generally affect ignition timing requirements?

Accepted Answer

Higher altitude typically requires more advanced timing due to lower air density and slower flame speed

Answer

At higher altitudes, the lower air density reduces the likelihood of detonation and slows flame propagation, generally allowing and requiring more ignition advance for optimal combustion efficiency.

CPT - Certified Performance Technician Practice Test

CPT - Certified Performance Technician Practice Test

CPT Ignition Systems & Timing 2