TURBULENCE

NZ Truth, Issue 1238, 22 August 1929, Page 19

TURBULENCE

More Power In The Engine

Few motorists have more than a vague idea of what is meant by the term "turbulent." ', A TURBULENT engine is one wherein ** the gases, at the time of ignition, are m an agitated or turbulent state. This conditipn can be obtained m a. number of ways; When the importance of turbulence was first appreciated, some designers attempted to. achieve it by obstructions m the induction system, so that, the gases were ftpinning when they, reached the combustion chamber, v.. x In this they" were directly opposed to the streamline school of thought, which aimed at getting- as. much gas as possible into the cylinder, irrespective of whether or not it was m the best condition for rapid combustion. It has been proved time- and again that turbulence provides' <n- . creased power, together with economy, - since it allows'combustion to be more complejte. The most recent way of obtaining it, however, is such that, as the' piston rises, the compressed gas is trapped between the piston and. the cylinder head, and is suddenly impelled into the combustion chamber, so producing the maximum turbulence just before ignition takes place. The mixture is thus, quickly burnt, and there is less tendency towards "pinking," even when the , engine is pulling hard at low speeds.. An important factor is the placing of the sparking plug on the exhaust side, so that the flame travels aWay from the hot exhaust valve towards the piston which has commenced the downward stroke, thus allowing more space for the remaining portion of the combustion process to take place. Due to the position of the. inlet valve, a stream of cool gas is directed on to the exhaust valve ' during' the suction stroke, thus providing a valuable cooling, effect. It is sometimes thought that for an, engine to be fast it must have a "fast" timing — i.e., must take a large amount of advance on the ignition. •* This, however, does not apply to a modern turbulent engine, for the gases themselves are more readily ignited than those m a non-turfiulent engine, and less ignition adyance.j.theref ore is required. : ' ; . ' "y^-yr ''■'■:'. "

■Water m the crankca/se is due to one of three general causes: ; Water m the gasoline or lubricating oil; a loose cylinder head gasket, a' cracked -cylinder from the water-jacket.