Haltech E6S - Manual (Page 62)

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8.3 The Ignition Coolant Map
The Ignition Coolant Map allows up to 10° advance or retard of the spark timing based on
engine coolant temperature. This Map should only be used if there is a need to adjust the
timing for low or high temperatures.
8.4 The Ignition Inlet Air Temperature Map
This Map allows up to 10° advance or retard of the spark timing based on the inlet air
temperature. Normally this Map would not need to be used, but in some cases such as high
inlet air temperatures on turbo/supercharged engine, retarding the spark may help preserve the
engine.
8.5 Barometric Correction
Fluctuations in barometric pressure varies the density of the intake air of the engine. At lower
barometric pressure, the engine can not breath in as much air, and therefore the amount of fuel
delivered to the engine must be reduced. In mapping in Throttle Position Mode, the Map
sensor provides a reading used for Barometric Correction. When in Manifold Pressure Mode,
there are three forms of Barometric Correction performed by the E6S.
The Manifold Absolute Pressure Sensor (MAP Sensor) supplied with the E6S measures the
absolute pressure of the air in the inlet manifold, and therefore automatically correct for small
changes in barometric pressure. For a given geographical area, small fluctuations in the
barometric pressure can be adequately handled by the MAP Sensor. This is the first form of
correction performed.
Larger fluctuations in barometric pressure are usually caused by a change in altitude. When
the E6S is powered on it runs a small test to determine the barometric pressure. As you should
have read earlier, the ECU switches the fuel pump on at start up (fuel pump prime). If the
engine is not started, the fuel pump will be switched off. At this time, the ECU also reads the
MAP Sensor. If the engine is not running, the MAP sensor will indicate the prevailing
barometric pressure. The ECU remembers this pressure and uses it to perform a barometric
correction on the fuel delivery. Small changes in the barometric pressure from that point are
then handled by the MAP Sensor. This is the second form of barometric correction the E6S
performs.