Haltech E8 - Manual (Page 89)

Haltech E11/E8 Instruction Manual
Figure 93 - Post Start Fuel Map
Barometric Pressure
If you are using MAP for load sensing on your engine, then it is unlikely that you will need to worry about
Barometric compensation for fluctuations in ambient barometric pressure. If you are using TPS for load
sensing, Zero Throttle maps or Full throttle maps, then read on to learn how to configure Barometric
Pressure compensation maps.
Fluctuations in barometric pressure vary the density of the intake air of the engine. At lower barometric
pressure, the air density is lower (there is less oxygen in the 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 ECU has an on board Barometric Pressure sensor that is used to measure the ambient air pressure.
To compensate for the fluctuations in atmospheric conditions, the Barometric Correction map allows
correction to your injection times of up to
± 50%.
Zero Throttle
One problem that often occurs with performance engines is rough idling. The manifold design, cam
characteristics, etc. can cause instability in the airflow. This makes fuel metering difficult. In particular, the
Map sensor often cannot correctly read the manifold pressure, as it is non-existent, weak, or pulsing too
much. In many cases though, once the engine has some speed, the manifold pressure signal is useable.
The best method of mapping the engine is using the manifold pressure as the load. If in this configuration
idling is causing a problem, the Zero Throttle Map should be tried. This Map maps the fuel delivery at zero
throttle below 2000 rpm. There are a few requirements that need to be met before you can use this Map.
Firstly, your throttle position sensor must be calibrated properly. Secondly, the Map relies on there being a
consistent airflow at zero throttle for a given engine speed. That means that devices such as idle speed
motors that vary the airflow at zero throttle will not allow the Zero Throttle Map to operate correctly.
Full Throttle
The manifold and throttle body design can also cause problems tuning at full throttle on normally aspirated
engines. In some cases, the manifold pressure can reach close to atmospheric pressure before full throttle
is reached. This means that bars close to the full load bar on the Fuel Maps can interfere with the full load
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