USING THE "SPARK"

Rotorua Morning Post, Volume 1, Issue 110, 31 December 1931, Page 2

USING THE "SPARK"

SUFFERS FREQUENT NEGLECT Although many cars now have automatic ignition control, there are still a number that have the manual control, and through ignorance or carelessness, or merely because they do not realise the effect of advancing and retarding the ignition, too many motorists fail to obtain the best results from their cars in respect to power and economy by making insufficient use of the ignition timing control — frequently called the "spark lever." The commonest fault is running with the lever too far retarded, probably owing to its having been observed that in this position there is no tendency for the engine to "pink" when it is pulling hard and slowly. That policy, however, encourages waste of fuel, over heating, burning of the valves and failure to secure the best results in power development. To take an extreme case, if an attempt be made to drive at, say 50 m.p.h. on a level road with the ignition lever fully retarded, approximateiy one-sixth to a quarter of the stroke of the piston is "wasted"; in other words, the fuel mixture in the cylinder is not fully ignited — the "explosion" is not complete— - until the piston , has travelled through a considerable proportion of. its movement on the power stroke. This implies, further, that the gases are still burning when the exhaust valve opens, so that the valve and its ' seatings are liable to be overheated,

and become pitted and due for regrinding after a very much smaller mileage than is normal, The best plan is always to keep the ignition as far advanced as possible short of giving rise to pinking. True, it is not possible in practice always j to secure that ideal, but it is one that j should be the aid of the driver. Roughly speaking, it means that at all speeds on top gear above 25-30 m.p.h. the 'ignition lever should be fully advanced.