HAMMOND LUMBER Co.

can be effected. ln sotne engines this saving uat' be considerablv greater.

Engine EfficiencY

The engine efhciency increases lvith the engine s1>eed up to a certiin limit. With higher speed engines the ignited gases expand more rapidly and the time of contact between ih. ttot gases and the c-r'linder walls -durin-g. each power stroke is-shorter. hence a smaller number of heat units is absorbecl or carried au,ay by the cylinder walls at each exolosion. '

In high compression engines tl-re combustion cl-ramber is smaller than in lorv compression engines, for this reason less cylinder rvall surface is exposed to the burning gas and this tends to rai-.e the efficiency of high compresiion engines. A higher compression pressttre gives also a considerably higher explosive Pressure.

75% oI EnergY Lost

Most o{ the heat units containetl in gasoline are lost either througl.r the cylinder r'r'alls or through the exhaust' Approximately l-3 of the energy is lost through the cylindir walls, 1-3 through the exhaust and only 1-3 is transformed into u'ork, under favorable conditions. Ordinarily more than /a of. the energy contained in gasoline is lost' Yet, a certain number of heat units must be allsorbed from the cylinder t,alls by the cooling system else the engine will iefuse to function as the pistons would become overheated ancl seize or bincl. If more than the required