Ignition Systems & Timing Flashcards
7 cards from real CPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ignition Systems & Timing flashcards as text
What is dwell angle in a conventional points-type ignition system?
Answer: The number of degrees the distributor cam rotates while the points remain closed
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.
What advantage does a coil-on-plug (COP) ignition system offer over a conventional single-coil system?
Answer: Each cylinder gets a dedicated coil, providing maximum energy and faster recharge time
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.
What is the primary role of a crankshaft position sensor (CKP) in a modern ignition system?
Answer: To provide the ECU with engine speed and piston position data for spark timing
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.
How does pre-ignition differ from detonation?
Answer: Pre-ignition occurs before the spark fires; detonation occurs after the spark fires
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.
How does higher altitude generally affect ignition timing requirements?
Answer: Higher altitude typically requires more advanced timing due to lower air density and slower flame speed
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.
What is the primary function of a knock sensor in a modern engine management system?
Answer: To detect detonation and signal the ECU to retard ignition timing
The knock sensor detects the high-frequency vibrations characteristic of detonation and sends a signal to the ECU, which retards ignition timing to eliminate the knock and protect the engine.
Why is the firing order of an engine important for performance technicians?
Answer: It ensures that power strokes are evenly spaced to minimize vibration and heat buildup in adjacent cylinders
The firing order is engineered to distribute power strokes evenly around the crankshaft and prevent adjacent cylinders from firing consecutively, which reduces vibration and avoids heat concentration in one area of the engine.