Haltech F10X - Manual (Page 62)

F10X Manual
62
9.3 Barometric Correction
NOTE:
The description that follows is targeted at advanced applications. Only limited
installations use barometric compensation.
If you are using a MAP sensor as your load reference we suggest that you set
the barometric lock in the fuel set-up to “disabled” and bypass this section.
If using throttle position for load sensing barometric compensation is required.
Please note that the default map for barometric compensation is flat and a
barometric compensation map must be compiled. See the sample map below.
Fluctuations in barometric pressure vary the density of the intake air of the engine. At lower
barometric pressure, the engine cannot breathe in as much air, and therefore the amount of
fuel delivered to the engine must be reduced. 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).
The barometric correction map is used by the ECU to determine the fuel adjustments required
for the given barometric pressure. The map shown below is typical of a barometric map used
in conjunction with throttle position load sensing.
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