Haltech F10 - Manual (Page 53)

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allow the injectors to be accurately flow tested over a range of battery voltages and the
corrections calculated accordingly.
8.5 Barometric Correction
Note: The description that follows is targeted at advanced applications and
unless you wish to compensate for exhaust back pressure or are using the
throttle position 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 a M AP
sensor for load sensing, barometric compensation is automatic as map sensors
are manifold absolute pressure sensors and the readings compensate for
barometric fluctuations. The only application using M AP sensors that would
require barometric compensation would be when the exhaust back pressure
must be taken into account. If using a M AP sensor we recommend that you set
“Barometric Lock” in the fuel set up page to “disabled” (i.e. barometric
compensation is enabled). However please note that if you are using throttle
position load sensing, instead of a M AP sensor, barometric compensation is
always required. Please note that the default map for barometric compensation
is flat and a barometric compensation map must be compiled. See the sample
map at the bottom of page 70. The barometric compensation map should be
compiled as shown on Page 70 before any tuning takes place to ensure proper
compensation.
Fluctuations in barometric pressure vary the density of the intake air of the engine. At lower
barometric pressure, the engine cannot breath 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 on the F10 is a powerful and therefore relatively
complicated feature and this section aims to describe the different methods it can be
implemented with. The above flowchart is an overview of the different barometric
compensation methods available with the F10.
The F10 begins with the basic idea that there are three ways to compensate for barometric
pressure variations.
- The first is to use a pressure sensor to continually supply the F10 with
barometric pressure data and then the F10 can adjust the injection times
based on this information.
- The second method takes 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.
- The third method is to use a preset value for barometric pressure,
irrespective of what is going on in the surrounding environment.
M ethod 3 is the most basic form of correction and will be our starting point. When the F10 is
manufactured it is configured with a value of 1013mBars as the constant barometric pressure.
NOTE: If you ever wish to return the F10 to the factory barometric pressure
settings then enable the Barometric Lock in the Fuel Set-up page and set the
Barometric Pressure Lock to 1013 mBars. These are the factory settings.