In automatic control, what does the pilot set and what adjusts turbo charging?

• A. Pilot sets required manifold pressure; aneroid capsule increases or decreases turbo charging
• B. Pilot sets RPM; spring adjusts
• C. Pilot sets fuel-air ratio; electronic actuator adjusts
• D. Pilot sets exhaust backpressure; damper adjusts

Answer: (A)

The automatic boost system works by keeping the intake manifold pressure at a value the pilot selects. The pilot sets the required manifold pressure, and an aneroid capsule acts as a pressure-sensitive controller that automatically adjusts turbocharger boost to maintain that setting as conditions change. As altitude increases and ambient pressure falls, the aneroid capsule expands and acts to increase boost (restricting the wastegate) to keep the manifold pressure from dropping. Conversely, at lower altitude, the capsule contracts and allows more wastegate opening, reducing boost so the manifold pressure doesn’t rise too high.

This is why the pilot’s action is about setting the manifold pressure, while the automatic mechanism handles boosting by responding to ambient pressure via the aneroid capsule. The other options don’t fit how automatic turbocharging maintains a chosen manifold pressure.