IGNITION TIMING

Hawera Star, Volume LII, 19 November 1932, Page 12

IGNITION TIMING

HOW SPARK AFFECTS POWER, How spark timing affects compeer, sion is little understood by the average motorist, vet it is easily explained. Sinee petrol vapour requires a mens arable time to burn, it is cu.s tom ar> to time the spark in the cylinders ti ignite the gas before the pistons read the top of their compression strokes With the spark properly advanced, enough of the gas should start burn ing to further compress its unburnee portion, so that when the pistons star; down on their power' stroke they ch so with greater force. If the spark is too early and to< much gas starts burning, the ten dene.' is for the pistons to be prevented fron reaching the top of their compressioi strokes. This causes pronouncee knocking, and during cranking result, in back-firing. The faster the engine runs the more, within limits, the spar! can. be advanced with safety and efficiency. In this way the ignitin': of the gas charge, itself affects com pression and power. This knowledge is elementary, but'if owners studied it: effects they would obtain better per formance from their cars. It should be remembered, too, tha the use of spark plugs that are oldei than 10,000 miles has a similar effec; to retarded ignition, because of the considerably weakened sparks at the plug points being incapable of ignitin' the cylinder charges efficiently.