Question 382Motor Plants - Assistant Engineer

The correct answer is A) effective cylinder scavenging and cooling. During the valve overlap period, when both the intake and exhaust valves are open, the exhaust pressure must be less than the intake manifold pressure. This pressure differential allows for effective scavenging of the cylinder, where the incoming fresh air can displace the exhaust gases and cool the cylinder. This ensures optimal engine performance and efficiency. The other options are incorrect because: B) constant pressure from the turbochargers is not the primary purpose of the valve overlap period, C) cooler operation of the exhaust system is not the main concern, and D) effective constant pressure for turbocharger operation is not directly related to the valve overlap period.