SPARK TIMING

Rotorua Morning Post, Volume 2, Issue 338, 27 September 1932, Page 2

SPARK TIMING

H,OW IT AFFECTS COMPRESSION. How spark timing affects compression is little understood by the average motorist, yet it is easily explained. ' Since petrol vapour requires a measurable period of time to burn, it is customary to time the spark in the cylinders to ignite the gas before the pistons reach the top of their*compression strokes. With the spark properly advanced eilough gas should start buring to compress further its unburned portion, so that when the pistons start down on their power strokes they may' do so with' greater force. If the spark is too early and too much gas starts burning the tendency is for the pistons to be prevented from reaching the top of their com_ pression strokes. This causes pronounced knocking, and during cranking results in baelc-firing. The faster ■ the engine runs the more, within. limits, the spark can be advanced with safety and effieiency. In this way the ignition of the gas charge itself affects compression and jiower. This knowledge is elementary, but if owners studied its effects they would obtain better performance from their cars. Superfluous flesh reduced easily and pleasantly by taliing- Youtb-o-form Capsules. 6/6. M. J. Spear and other Chemists.