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

Modern ignition systems must generate 12,000 to 45,000 volts in the secondary circuit to ionize the spark plug gap and fire reliably under the pressures and temperatures present in the combustion chamber.

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

Heat range describes how quickly a spark plug transfers heat from its insulator tip into the cylinder head cooling system; a 'hotter' plug retains more heat, while a 'colder' plug dissipates heat faster.

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

Retarded timing causes combustion to occur too late in the power stroke, reducing the mechanical work extracted from the expanding gases and increasing exhaust temperatures as burning continues into the exhaust stroke.

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

MSD systems fire the spark plug multiple times per compression event at low engine speeds (typically below 3,000 RPM), ensuring complete combustion of the air-fuel mixture when crank rotation is slow enough to allow it.

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

Total timing is the combined ignition advance at a given operating condition, including the initial base timing plus all centrifugal and vacuum advance added by the distributor or ECU.

CPT - Certified Performance Technician Practice Test

CPT - Certified Performance Technician Practice Test

CPT Ignition Systems & Timing 3