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 does ignition timing refer to in an internal combustion engine?
Answer: The moment the spark plug fires relative to piston position
Ignition timing refers to the precise moment the spark plug fires in relation to piston position, typically expressed in degrees before or after top dead center (TDC).
What is the primary purpose of an ignition timing advance mechanism?
Answer: To allow combustion to complete optimally as engine speed increases
As engine RPM increases, combustion must begin earlier (advance) so the expanding gases reach peak pressure at the optimal piston position, maximizing power output.
Which tool is used to dynamically measure ignition timing on a running engine?
Answer: Timing light (stroboscope)
A timing light uses strobe flashes triggered by the ignition signal to freeze the timing mark on the crankshaft pulley, allowing technicians to read dynamic timing while the engine runs.
What is engine knock (detonation) in relation to ignition timing?
Answer: Uncontrolled ignition of the air-fuel mixture before or simultaneously with the spark
Detonation occurs when the air-fuel mixture auto-ignites due to heat and pressure rather than the spark, creating a sharp pressure wave that produces a knocking sound and can damage engine components.
What is the difference between static timing and dynamic timing?
Answer: Static timing is measured with the engine off; dynamic timing is measured with the engine running
Static timing is set with the engine off using a reference mark, while dynamic timing is checked with the engine running using a timing light to account for centrifugal and vacuum advance.
What is the primary function of a distributor cap in a conventional ignition system?
Answer: To regulate voltage to each spark plug in firing order sequence
The distributor cap routes the high-voltage secondary current from the coil to each spark plug wire in the correct firing order sequence as the rotor spins inside.
What is a primary advantage of a distributorless ignition system (DIS) over a conventional distributor-based system?
Answer: DIS eliminates mechanical wear points and allows individual cylinder timing control
Distributorless ignition systems remove the mechanical distributor, eliminating wear on the cap and rotor, while also enabling the ECU to control timing on a per-cylinder basis for optimized performance.