Show VALVE TIMIS TIMING IS IMPORTANT If I Upon Up on Which Au Au- Automobile Automobile Automobile Experts Not Agreed I The rhe subject ot of valve timing If is ono one of which the engineers eng have not Agreed greed as there are soy soy- sev several Oral eral factors which determine the tho of or lead load to be given to the salvos Alvos The most Important of these are arc the size of or the valves their loca loen- loca- loca location location tion and the tho average speed of ot the Theoretically each cycle of or the cylinder I four cylinder engine begins begin and aneS ends at the tho top or bottom dead con cn tel ter of ot piston tra tinsel el LIke Likewise Ise th th valves should open and close at the beginning and end of or the cycle In I actual practice however it has been found Cound necessary to tc to vary the timing some hat from front the tho the the the- correctness owing to the Inertia of Gt the tho gases cues Inertia Is la that property of or all masses that tends to resIst a II change chang of ot state hethel that state be rest or movement If Ita 0 valve opens oens or r closes before the dead center ot of o piston travel that distance I 1 is known as lead It It opens or closes cloes after dead center I It Is known as s lag These distances are measured In angular movement of the crankshaft If It a valve Is IsI I given a II fifteen degrees lag It means meAn that the crankshaft is fifteen do- do do gres gnes past dead center bet before ore the valve begins to function A As the volume or of o the exhaust gases Is much greater than the Ibe vol- vol volUme vol volume ume of the gasoline vapor before lume IgnItion it hat has been found in ad- ad advantage ad advantage vantage Vant to give elvo th valves a certain amount of lead Iced on opening In order to facilitate the removal of the gases gMt'S Though this may Waste some of ot the force of ot the eXI explosion lo lon It a 0 a greater freedom of r the thO th pIston in commencIng inc tue stroke For the tho same salDo reason renson the I exhaust valves are also given a certain tain Lain amount of or lag OR la on closing When tho the piston rises on the ex- ex exI ex exhaust I haust baut stroke the tho exhaust iso ga-iso can can- hot can n hot pass out of ot the tho cylinder all aS quickly as aa the tho piston travels and therefore are slightly compressed Should the valves close at some of these center the tho top tOl dead still sUII remaIn would compressed gases beginning ot of In the cylinder at the tho This would not IntAke stroke the thO Incoming gas gos contaminate the only entrance also but ot of the fresh Digest e |