Haltech E6X Manual DOS Version - Manual (Page 75)

E6X Manual
75
The ECU begins with the basic idea that there are three ways to measure barometric pressure
variations.
1. The ECU uses a user programmable value for barometric pressure, regardless of
the current environmental conditions.
2.
The ECU uses a pressure sensor to take a barometric pressure sample from the
environment when the car is first turned on and uses this value for the remainder of
the time the car is operated. This method of compensation is limited to
applications that use a MAP sensor for load sensing.
3.
The ECU uses a pressure sensor to continually measure the barometric pressure
during operation of the engine.
9.5.1 Barometric Correction - Method 1
This method requires the user to access the Fuel Set-up page and adjust two fields.
- Set “Barometric Lock” to “Enabled”. This tells the ECU that you are going to
lock a particular value in as the barometric pressure value.
- Set “Barometric Pressure Lock at” to “xxxx mBar”. This field tells the ECU the
barometric pressure as measured by the user. This value should be the average
barometric pressure the engine will be operated in.
Barometric pressure changes regularly and Method 1 is only a basic approach at barometric
compensation. Set the Barometric Pressure Lock at xxxx mBars, where xxxx is the pressure
you require, for example the measured barometric pressure is 1000mBars. When the fields
have been set (as described above) the ECU will assume that the environment always operates
at 1000mBars barometric pressure. The ECU will look at the Barometric Correction Map and
locate the 1000mBars section of the map. The height of the bar corresponding to 1000mBars
will be taken as the overall enrichment %.
9.5.2 Barometric Correction - Method 2
This method uses a barometric pressure reading taken prior to cranking the engine. This
method is restricted to applications that use MAP sensors for load sensing.
This method requires the user to access the Fuel Set-up page and a field.
- Set “Barometric Lock” to “Disabled”.
When the ECU is powered up, it will run a small test to determine the barometric pressure.
During power up the ECU switches the fuel pump. 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 current barometric pressure. The ECU remembers
this pressure and uses it to perform a barometric correction on the fuel delivery.
If at start up the engine is cranked before the fuel pump prime has finished the ECU cannot
read the barometric pressure from the MAP sensor, as the engine will be applying a vacuum.