THE IGNITION LEVER

Press, Volume LXIX, Issue 20955, 8 September 1933, Page 15

THE IGNITION LEVER

DRIVERS WHO RETARD IT TOO PAR On cars not fitted with automatic ignition control many drivers, because they do not realise the effect of advancing and retarding the ignition, fail to obtain, the best results .from their cars in respect of power and economy by making insufficient use of the timing 'control —frequently called the "spark lever." The commonest fault is runnihg 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, overheating, 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 miles an hour, on a level road with the ignition lever fully retarded, approximately 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 ns possible, short of giving rise to pinking. True, it is not possible in practice always to secure that ideal, but it is one that Should be the aim of the driver. Roughly speaking, it means that at all speeds on top gear above 25-30 miles an hour the ignition lever should be fully advanced. {