Haltech E6A - Manual (Page 63)

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If at start up the engine is cranked before the fuel pump prime has finished the ECU can not
read the barometric pressure from the MAP sensor as the engine will be applying a vacuum to
it. In this case, the E6A will use a pressure reading stored in its memory. This reading is set to
one atmosphere at sea level (1013 millibars) at the factory. This value can be reset to a
pressure that is close to what is expected in the geographic area the engine will be used in. To
reset this value, follow these steps :
1. Firstly make sure the throttle position sensor is properly calibrated. It must exceed
96% throttle for this to work. Also make sure that the MAP Sensor is set correctly
in the Identification.
2. Switch the ignition off.
3. Apply full throttle.
4. Switch the ignition on but DO NOT crank the engine.
5. Wait till the fuel pump prime finishes (about 5 seconds) then release the throttle. The
current barometric pressure as read by the MAP Sensor will be programmed into
the ECU’s memory.
It is not necessary or advisable to perform this reset regularly. It should only be done if
the vehicle’s regular place of garage is moved or if problems are suspected in the barometric
correction. For example, if an engine is tuned at sea level but is intended to be used mainly at a
higher altitude, then the reset should be performed once it reaches its new regular location.
After that, the automatic reading done at start up will be sufficient.
The third form of Barometric Correction is performed using a separate Barometric pressure
sensor. With a 1 Bar MAP Sensor (left open to atmospheric pressure) connected to the Spare
Input, any changes in barometric pressure can be compensated for immediately. This is
necessary when a large change in altitude is expected during a driving period (a Hill Climb
event such as Pikes Peak in the USA is a good example).