CPT Ignition Systems & Timing 3

Question 1

What secondary voltage is typically required to fire a spark plug under normal compression in a gasoline engine?

Accepted Answer

12,000–45,000 volts

Answer

1,000–3,000 volts

Answer

5,000–8,000 volts

Answer

100,000–150,000 volts

Question 2

What does the heat range of a spark plug indicate?

Accepted Answer

The plug's ability to transfer heat from its firing tip to the cylinder head

Answer

The maximum combustion temperature the plug can withstand before melting

Answer

The voltage range across which the plug will reliably fire

Answer

The recommended coolant temperature for the engine the plug is designed for

Question 3

What symptom is most commonly associated with ignition timing that is excessively retarded?

Accepted Answer

Loss of power, poor fuel economy, and excessive exhaust heat

Answer

Engine overheating and detonation under light loads

Answer

Backfiring through the intake manifold at idle

Answer

Erratic idle speed and vacuum leak symptoms

Question 4

What is a multi-spark discharge (MSD) ignition system designed to do?

Accepted Answer

Deliver multiple spark events during the compression stroke at low RPM to improve ignition reliability

Answer

Fire multiple spark plugs per cylinder simultaneously for improved combustion

Answer

Increase secondary voltage to spark plugs by stacking coil output signals

Answer

Retard timing in multiple increments to prevent detonation

Question 5

What does the term 'total timing' refer to in performance engine tuning?

Accepted Answer

The sum of base timing and all forms of timing advance (centrifugal and vacuum)

Answer

The total number of degrees the crankshaft rotates during one complete engine cycle

Answer

The combined ignition advance from both the primary and secondary coil circuits

Answer

The elapsed time in milliseconds from spark to full combustion pressure

Question 6

What is the purpose of vacuum advance on an older conventional ignition system?

Accepted Answer

To advance ignition timing during light-load, part-throttle cruise for improved fuel economy

Answer

To advance ignition timing under high engine load and wide-open throttle conditions

Answer

To retard timing when manifold vacuum drops below a calibrated threshold

Answer

To compensate for centrifugal advance loss at low engine speeds

Question 7

How does an increased compression ratio generally affect ignition timing requirements?

Accepted Answer

Higher compression requires retarded timing or higher-octane fuel because the denser charge is more prone to detonation

Answer

Higher compression allows more timing advance because burn rate decreases with denser charge

Answer

Compression ratio has no effect on ignition timing requirements

Answer

Higher compression always allows the same timing as lower compression with premium fuel