Question 21Motor Plants - Assistant Engineer

The correct answer is A) The combustion gases have expanded. The line connecting points 'd' and 'e' on the pressure-volume diagram represents the expansion stroke of the engine cycle. During this stroke, the combustion gases produced from the fuel/air charge ignition expand, pushing the piston down and creating the power to rotate the crankshaft. The other options are incorrect because: B) The crankshaft has rotated 90° is not directly indicated by the line between 'd' and 'e'; C) Pressure and volume have increased is the opposite of what happens during the expansion stroke; and D) The fuel/air charge is compressed occurs earlier in the engine cycle, not during the expansion stroke.