This tab contains MAP Sensor parameters. Also see MAP Sensor Installation
Warning : Exceeding the MAP sensor upper pressure limit will result in the engine running lean.
Warning : Setting the boost limit beyond the MAP sensor upper pressure limit will result in the boost limiter not functioning.
The MAP (manifold absolute pressure) sensor reads air pressure in the intake manifold to determine engine load. It is the primary sensor in determining fuel, ignition and other requirements of the engine. The stock MAP sensor can read pressure to approximately 1.8 bar (11.4 lbs boost pressure). Beyond this value a replacement MAP sensor is necessary. Any sized linear 5V MAP sensor can used - which is virtually any MAP sensor.
Tab Parameters
MAP Sensor Selection
Either the stock MAP sensor or an alternate sensor can be used. If the stock MAP sensor is selected then the stock voltage to pressure conversion is used - you do not need to enter anything in the Voltage to Pressure conversion section of the tab.
Quick Select
Selects from a number of pre-set voltage to pressure conversion parameters. If the MAP sensor you are using is not listed then you will need to enter a custom conversion.
Scalar
The scalar (multiplication value) for the MAP sensor voltage to pressure conversion. For more information see scalar & offset.
Offset
The offset for the MAP sensor voltage to pressure conversion. For more information see scalar & offset.
Full Scale Values
This calculates the full scale pressure readings at in mbar and lbs boost. Note that these values are calculated at 5V and may not be achievable due to differences in supply voltage from the ECU. See Boost Limit for more information.
Atmospheric Pressure Values
This calculates the expected voltage at standard atmospheric pressure (1013.2 mbar). Note that not all MAP sensors will report atmospheric pressure under key-on-engine-off conditions.
Scalar & Offset
A MAP sensor converts a pressure reading into a voltage output. There is a relationship between output voltage and pressure which determines the pressure range of the MAP sensor. This relationship should be linear (otherwise the MAP sensor is poor quality) and therefore can be described using a linear equation.
The scalar and offset describe the pressure / voltage equation. These values may be determined by measuring the voltage output from the MAP sensor and plotting on a graph, or from the specifications of the MAP sensor.
If you do not know the scalar or offset for a MAP sensor then please do not guess.
Boost Limit
The boost limit operates when the manifold pressure exceeds a pre-set value. The value must be within the range of pressure that the MAP sensor can read, with a margin for production tolerances on the ECU sensor output voltage and MAP sensor. You must not assume that a 5V MAP sensor will reach 5V output at maximum pressure. e.g. the boost limit is set to 11.3 lbs for a stock MAP sensor, which equates to an output voltage of 4.96 V from the MAP sensor. This is too close to the maximum output of the MAP sensor for reliable triggering of the boost cut (the MAP sensor might never exceed 4.9 V for instance). It is recommended that a 1 lb or 0.2V margin is left between the boost cut and MAP sensor maximum pressure reading.