DOE-HDBK-1018/1-93FUNDAMENTALS OF THE DIESEL CYCLEDiesel Engine FundamentalsAt 43ABDC, the camshaft starts to close the exhaust valve. At 53 ABDC (117BTDC), the camshaft has rotated sufficiently to allow the spring pressure to close theexhaust valve. Also, as the piston travels past 48ABDC (5 after the exhaust valve startsclosing), the intake ports are closed off by the piston.Figure 21 2-Stroke ExhaustFigure 22 2-Stroke IntakeCompressionAfter the exhaust valve is on its seat (53 ATDC), the temperature and pressure begin torise in nearly the same fashion as in the four-stroke engine. Figure 23 illustrates thecompression in a 2-stroke engine. At 23 BTDC the injector cam begins to lift theinjector follower and pushrod. Fuel injection continues until 6 BTDC (17 total degreesof injection), as illustrated in Figure 24. ME-01Rev. 0Page 26
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