Auto Electrical Works Paper 2, May/June 2015

Question 3

What is meant by ignition timing being advanced?
List;
Why is it necessary for the timing to advance when the engine runs faster?

Observation

The expected answers were;

Definition of advance ignition timing

Ignition timing is the setting of the point at which the sparking fires relative to where the piston is in the cylinder. The highest point the piston can go is called Top Dead Center (TDC), timing is set for number of degrees of crankshaft rotation before the TDC. The number of degrees is determined by the factory, and since it’s setting the plug to fire before TDC, it is called the timing advance.

(i) Types of ignition system

(a)Contact breaker/conventional ignition system (b)Electronic /transistorized ignition system (c)Programmed/computerized ignition system (d)Direct ignition system (e)Magneto ignition system

(ii) Ignition system components

(a) Distributor cover (b)Ignition switch/key (c)High Tension Lead (d)Battery (e) Coil (f) Spark plug (g) Cable/conductor (h) Ignition fuse (i) Carbon rod/brushes (j) Condenser (k)Contact set/ breaker point (l)Rotor (m)Resistor

Reasons for advancing ignition timing

When the spark plug fires in the combustion chamber, it ignites the fuel and air mixture. In order to maximize the amount of power generated, the spark plug must fire before the piston reaches the top of the cylinder so that the burning fuel is ready to push the piston down as soon as it is at the top of its panel. The faster the engine is spinning the earlier we have to fire the plug to produce maximum power.

The timing need to be advanced for the smooth operation of the engine

The candidates were expected to explain advance ignition timing, list two types of ignition system, and five components of ignition system. State why timing is to be advanced as the engine runs faster.
The candidates’ performance was reported to be average in this question.