Ignition Timing

Introduction:
Ignition timing is the correct instant of generating spark just before the completion of compression stroke. Correct, ignition timing is necessary to maximize power output of an engine.

Need for ignition timing:

Correct ignition timing is necessary to maximize the performance of the engine. Correct ignition timing depends upon several factors.

These are compression ratio; diameter (bore) of cylinder, composition of mixture, engine speed and load, engine temperature and quality of fuel used. Except first two factors other factors keep on changing.

Therefore, there must be an automatic mechanism of adjust the ignition timing of engine.

Sometimes the spark is to be advanced and sometimes it is required to be retarded.

Static ignition timing:

For the engine to run efficiently and develop the proper power, the spark must occur at the right time.

This is controlled by adjusting the position at which the cam in the distributor opens the points relative to the position of the crankshaft (the distributor body position is adjusted so the points open at the correct crankshaft position).

Most engines (for reasons beyond the scope of this document) require the static ignition timing be set so the ignition points open several degrees before the piston reaches top dead center (BTDC).

Setting the static timing is a simple task but care needs to be taken when making these adjustments that they are being carried out for the correct cylinder at the correct step in the four-cycle process.