In an automatic variable wastegate system, which component is used to vary boost to meet the required manifold pressure?

• A. Throttle
• B. Aneroid capsule
• C. Waste gate
• D. Pressure sensor

Answer: (C)

In a system that automatically manages turbo boost, the thing that actually changes how much boost you get is the wastegate. Its job is to control how much exhaust energy goes to the turbine. When manifold (boost) pressure gets high, the actuator opens the wastegate to bypass exhaust away from the turbine, which cuts the turbine’s speed and lowers boost. When boost is too low, the wastegate closes, allowing more exhaust to drive the turbine and increase boost.

The aneroid capsule and the pressure sensor are sensing/feedback elements that help determine how much to adjust the wastegate, but they don’t directly vary the boost themselves. The throttle controls intake in naturally aspirated engines and isn’t what sets turbo boost in this system.