Which statement about volumetric efficiency (VE) is true?

• A. The statement is true: VE can be increased by using larger valves and improving the intake manifold design.
• B. The statement is false: VE cannot be increased by design changes.
• C. VE is unaffected by valve size and intake manifold design.
• D. VE depends only on cam timing and exhaust pressure.

Answer: (A)

Volumetric efficiency measures how well the engine fills its cylinders with air during the intake stroke. It can be increased by reducing restrictions in the air path from the throttle to the cylinders. Larger valves provide a bigger opening, lowering flow losses and allowing more air to enter, especially at higher engine speeds. A well-designed intake manifold helps balance and smooth air delivery to each cylinder, further reducing impedance and improving filling. Because these design changes directly affect how much air can be drawn into the cylinders, they can raise VE, so the statement is true. While cam timing and exhaust backpressure influence the filling process, VE is not controlled by them alone; other factors such as valve size and intake geometry play significant roles.