A Haltech MAP sensor (manifold absolute pressure) provides instantaneous pressure information to the electronic control unit (ECU) from the intake manifold - the amount of boost or vacuum in the intake manifold. This is necessary to calculate air density and determine the engine's air mass flow rate or in other words engine load. Engine load is used as a reference for all base fuel and ignition maps. 1 Bar Map Sensor A 1 bar MAP sensor is capable of reading intake pressures below or equal to atmospheric pressure, for this reason a 1 bar MAP sensor is suitable only for naturally aspirated engines (ie not turbo or supercharged). 3 Bar Map Sensor A 3 bar MAP sensor is capable of reading intake pressures up to 2 bar of positive pressure above atmospheric (otherwise known as boost). This is equivalent to around 29.4psi of boost or 200kpa of positive pressure. This sensor is suitable for turbocharged or supercharged vehicles running between 15psi and 30psi of boost.
