Manifold Pressure is defined as what?

Manifold Pressure is defined as what?

• A. Absolute pressure as measured at the induction system, expressed in inches of mercury
• B. Ambient pressure at sea level
• C. Dynamic pressure in the airstream
• D. Fuel pressure in the injection line

Answer: (A)

Manifold pressure is the absolute pressure inside the engine’s induction system (the intake manifold) that the air-fuel mixture sees, measured in inches of mercury. This is an absolute reading, not a gauge relative to ambient. In a normally aspirated engine, the throttle creates a vacuum in the manifold, so the pressure is below ambient and rises toward ambient as you open the throttle. In a boosted engine, such as with a turbocharger, the manifold pressure can exceed ambient due to boost. This reading is distinct from ambient sea-level pressure, dynamic ram pressure in the airstream, or fuel pressure in the injection line—the latter two are different system pressures.

Manifold pressure is the absolute pressure inside the engine’s induction system (the intake manifold) that the air-fuel mixture sees, measured in inches of mercury. This is an absolute reading, not a gauge relative to ambient. In a normally aspirated engine, the throttle creates a vacuum in the manifold, so the pressure is below ambient and rises toward ambient as you open the throttle. In a boosted engine, such as with a turbocharger, the manifold pressure can exceed ambient due to boost. This reading is distinct from ambient sea-level pressure, dynamic ram pressure in the airstream, or fuel pressure in the injection line—the latter two are different system pressures.