Show VALVE VE T r NG REFFES D Small Waste Vaste Allowed So That Efficiency Is Heightened subject of ot valve salse timing Is Isone iSone laone one on which time the base 0 not thoroughly agreed as there are which a determine the amount mount of lead head to 10 be ba g I Ito to the valves nl s Tho most important of these are the size of ot the Uses ll I their location and the tho a speed of tit the engine I Theoretically each cycle crele of th thol four C cylinder engine begins on an n I at the top or bottom dra deal 1 center of it pistol true trivel Likewise tI t o C nl should open and clos I at tIme the beginning and en end of the C cle In practice however It has been found necessary to 10 I Rry sac the time valve salse timing tinting t from froni the theoretical correctness I owing to th time Inertia of or time the g-as g gases Inertia is Ii that property of oC ill illI I masses that tends to resist a aI achang change chang of or te t hether hether that s state tn I ho bo ri rost st or moos movement mo at If lC a n 1 0 il o opens or closes Ioles before the tho Ie ci nto of o piston that t ills ills- d s It t I tarp CP Is Ii n as ns l lend head It if It onen lor I or closi closs S lItter liter lead olad center renter It Is Inon Loom as IRS ha las These distances ar are ar- ar measured in 10 1 movement of f th the crankshaft rt It If a n valve salse nh e Is gisen h en enn n a IS 1 lae la it means thit th th the crankshaft Is 10 Hj 15 degress past deal dead before tho the valve aho also begins to lO I function I As the time volume of ot the exhaust I is much greater than tho thio I o of tho the gasoline vapor apor tore lift I b-I be- be before fore foro I It hiss has 1 been een foun an ad advantage antage to give gise the exhaust I Ian a certain amount of ot lead leadin leadon on in opening opening- in order to the removal remo of C tho the gases eases I I this may waste at some sonie of the tho force ot of the It permits 01 a greater renter freedom of the piston I I commencing the exhaust For or the same reason the tile S alves are also glen given a certain amount of leg lag on closing When hm the piston rises on the stroke the exhaust gases cannot I pass out of the cylinder linder as quickly as the piston tr nn and l there there- 1 i I fol for are Should the exhaust haust close at the tho top dead dad center some of a thea sea gases Would still remain In th time the C chiner cv liner at the beginning of oC the Intake stroke This would ouM not only contaminate the tho Incoming gas but would also retard the of the fresh charge automobile Digest |