Question

In a four stroke I.C. engine, the turning moment during the compression stroke is

(a) positive throughout

(b) negative throughout

(c) positive during major portion of the stroke

(d) negative during major portion of the stroke

This question was posed to me by my school teacher while I was bunking the class.

This key question is from Flywheel topic in portion Turning Moment Diagrams and Flywheel of Machine Dynamics

Answer 1

Correct choice is (b) negative throughout

The explanation is: Since the pressure inside the engine cylinder is less than the atmospheric pressure during the suction stroke, therefore a negative loop is formed. During the compression stroke, the work is done on the gases, therefore a higher negative loop is obtained.