Question 25Motor Plants - QMED

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 the fresh intake air to effectively scavenge the exhaust gases from the cylinder, improving cylinder scavenging and cooling. The other options are incorrect because: B) is about maintaining constant pressure from the turbochargers, not cylinder scavenging; C) is about the exhaust system, not the pressure relationship during valve overlap; and D) is about maintaining effective constant pressure for the turbocharger, not cylinder scavenging.