4 x 4 Australia - - Tech Torque -

ATKIN­SON cy­cle en­gines are com­mon­place to­day in petrol-elec­tric hy­brids. How­ever, these mod­ern Atkin­son cy­cle en­gines are very dif­fer­ent to the orig­i­nal Atkin­son cy­cle en­gine(s) which date back to the 1880s, even if they do share a com­mon prin­ci­ple.

James Atkin­son came up with a num­ber of de­signs, the most fa­mous of which man­aged to pro­vide in­take, com­pres­sion, power and ex­haust strokes in one rev­o­lu­tion of the crank­shaft via a com­plex link­age ar­range­ment. Con­ven­tional Otto cy­cle en­gines need two rev­o­lu­tions of the crank­shaft to achieve the same thing.

All of Atkin­son’s de­signs had one thing in com­mon, namely the com­pres­sion stroke was shorter than the power stroke. Mod­ern Atkin­son cy­cle en­gines achieve a sim­i­lar ef­fect by de­lay­ing the clos­ing of the in­take valves un­til after the start of the com­pres­sion stroke. This leads to im­proved ther­mal ef­fi­ciency when power pro­duc­tion isn’t para­mount.

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