Chapter 34 PowerPoint

Define these Technical Terms using the textbook:

1. camshaft position sensor

2. manifold absolute pressure sensor

3. direct ignition system

4. engine coolant temperature sensor

5. engine firing order

6. ignition coil

7. ignition system

8. ignition timing

9. intake air temperature sensor

Answer these discussion questions using the textbook:

1. Explain the need for accurate ignition timing control.

Read the chapter summary below:

■ An ignition system amplifies battery voltage (12.6 volts) or charging system voltage (13 to 15 volts) to over 40,000 volts, and delivers this voltage to the spark plugs at the right time.

■ The primary circuit of the ignition system consists of all the components and wires that operate on low 12-volt dc from the battery, alternator, or current from the HV power control module.

■ The secondary circuit of the ignition system includes all the components that carry high-voltage current.

■ The secondary operating voltage of the ignition system can range from 4,000–100,000 volts, depending on system design.

■ The spark plugs use ignition coil high voltage to ignite the fuel mixture.

■ An ignition coil is a pulse-type transformer capable of producing the short bursts of high-voltage current that pass through the secondary resistance wires (if used), and jump the spark plug gap.

■ A coil pack ignition system, also called a distributorless ignition, uses multiple ignition coils, a coil control unit, engine sensors, and a computer (engine control module) to operate the spark plugs.

■ In a direct ignition system, one coil assembly is mounted directly above each spark plug, eliminating the need for spark plug wires.

■ In a dual spark plug ignition system, two spark plugs are used in each cylinder.

■ A multiple discharge ignition system fires the spark plugs more than once on each power stroke, which ensures more complete burning of the fuel charge.

■ An ignition distributor is used on older ignition systems to distribute the coil’s high-voltage pulses to the spark plug wires.

■ Engine firing order refers to the sequence in which the spark plugs fire to cause combustion in each cylinder.

■ Ignition timing must change with changes in engine speed, load, and temperature.

■ An electronic spark advance system uses engine sensors, an ignition control module, and/or a computer (engine or powertrain ECM) to adjust ignition timing.