Haltech F9A - Manual (Page 54)

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Chapter 8
Correction Factors
The Haltech F9 has two further correction maps to compensate the fuel for changes in inlet air
temperature and battery voltage, and also two correction Maps to adjust ignition timing for
coolant and inlet air temperatures. MOST USERS SHOULD NEVER ADJUST THESE
MAPS. These maps are factory set to provide excellent correction for almost all engines.
These maps should not be adjusted unless the user has experimentally derived data that the
correction factors could be better customised to suit a particular engine. When the F9 software
is run in the Offline mode, the software will load factory-set correction maps unless other
maps are loaded.
8.1 Fuel Versus Air Temp Map
The mass of air entering the inlet manifold varies with the temperature of the air. To
compensate for this, the F9 uses the Fuel Air Correction Map. The values supplied in your
ECU have been mathematically determined to give the optimal correction for most engines.
The Fuel Air Correction Map is accessed via the Fuel Maps and Setup Menu. Across the
bottom of the map displayed is the inlet air temperature. An arrow appears showing which bar
the system is currently using.
The map displayed is split by a horizontal line. Bars above this line indicate a positive
correction making the mixture richer. Bars below the line indicate a negative correction
making the mixture leaner.
A typical Fuel Versus Air Temp Map was loaded into your F9 at the factory. You should not
modify it unless you experience trouble with variation in engine performance with air
temperature.
8.2 The Battery Voltage Map
The Haltech F9 uses intelligent fuel injection driver circuitry that compensates for changes in
battery voltage. This compensation can be insufficient for the full range of battery voltages
that a vehicle's electrical system may experience. As the battery voltage falls, the injectors
will take longer to turn on and so reduce the effective open time. To compensate, the F9
applies the Battery Voltage Map to increase the injector on-time as the voltage drops. This
map should not be altered unless the system is connected to a fuel injector test bench that will
allow the injectors to be accurately flow tested over a range of battery voltages and the
corrections calculated accordingly.