SPARK TIMING

Rotorua Morning Post, Volume 2, Issue 386, 22 November 1932, Page 2

SPARK TIMING

_ Kow spark-timing aifects compression is little understood by the average motorist, yet it is easily explained. Since petrol vapour requires a measurable time to bum, it is customary to time the spark in the cylinder to ignite the gas hefore the pistons reach the top of their compression strokes. With' the spark properly advanced, enough of the gas should start burning further to compress its unburned portion, so that when the pistons start down on their power strokes they do so with greater force. If the spark is too early and too much gas starts burriing, the tendency is for the postons to be prevented from leaching the top of th'eir compression strokes. * This causes pronounced knocking, and during erartkihg results m backfiring. The faster the engine runs the more, within limits ,the spark can be advanced with saf eiy and efficrency. In this way the igniting of the gas charge itself affects compression and power. This knowledge, is ehunentary, but if owners studied its effects they would obtain hetter perfoimances from their cars. It should he remembered, too, that Se Uin nLSp,ark plugs that older than 10,000 miles has a similar effect to retarded ignition, because of the eonsiderably weakened sparks at the plug pomts being ihcapable of igniting the cylinder charge efficiently.