What does a manifold gauge measure in an engine?

A manifold gauge measures the absolute pressure within the engine manifold. This pressure is crucial for understanding the engine's performance because it directly relates to the air-fuel mixture entering the engine. When an engine is operating, the manifold pressure will vary depending on factors such as engine load, throttle position, and altitude. By assessing this pressure, mechanics and operators can determine how efficiently the engine is functioning and make necessary adjustments to maintain optimal performance. This gauge is integral in diagnosing issues related to fuel delivery, engine efficiency, and overall power output.

In contrast to manifold pressure, fuel pressure gauges measure the pressure of the fuel system, oil temperature gauges monitor the heat of the engine oil, and temperature gauges indicate the operating temperature of the engine, none of which provide the specific information that a manifold gauge does regarding the engine's intake air pressure.