What does a Manifold Pressure Gauge measure in a supercharged engine?

A manifold pressure gauge measures the absolute pressure in the induction manifold of a supercharged engine. This gauge provides critical information about the air density and the efficiency of the supercharging process. In a supercharged engine, the manifold pressure is usually higher than atmospheric pressure because the supercharger compresses the intake air before it enters the combustion chamber. By displaying the absolute pressure in the manifold, the gauge helps engineers and operators assess the engine's performance, detect potential issues with the supercharging system, and optimize engine tuning.

This measurement is crucial as it directly influences the amount of air available for combustion, thereby affecting engine power output and efficiency. Monitoring manifold pressure ensures that the engine operates within its design limits and can prevent conditions that may lead to engine knock or other performance problems.