Nira i7x - Volumetric Efficiency (VE) Table; Setting Up Appropriate X- and Y-axes

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VE comp = √k – 1
This formula changes depending on the type of fuel. E.g. methanol cools
more efficiently than gasoline so the VE comp value needs to be lower for
higher MAT values. The formula also depends on the placement of the
injectors; the further away from the intake valves, the higher the cooling
effect of the intake air.
6.3.3 Volumetric Efficiency (VE) Table
The VE value describes what ratio of the cylinder volume gets filled during
each intake stroke. The VE varies across changing RPM and MAP values and,
as described above, VE varies between the engine’s cylinders. It can be
thought of as a sign of how well the engine breathes under different
conditions. A high VE value means it breathes well and produces high torque
without boost pressure.
A V.E. value above 1.0 means there’s some amount of supercharging due to
resonance, without a turbo or supercharger. I.e. the pressure in the cylinder is
higher than the ambient pressure even before the piston starts compressing
the air. Using the VE table you can tell in what region your engine breathes
most efficiently. A higher VE value results in NIRA i7x injecting more fuel.
If the real-world lambda sensor values are different from the lambda table
values, then the VE table is off.
The idea behind fuel mapping in NIRA i7x is that once VE has been
established you never have to touch the fuel calibration again unless you
change something on the engine that effects VE significantly, such as the
intake, exhaust or the camshafts.
Setting Up Appropriate X- and Y-axes
Select a scale which corresponds to the appropriate range for the value in
question.
If the MAP value is never expected to exceed 260kPa absolute (1.6 bar boost
pressure), then pick 260kPa as the max value on the y-axis in the VE table.
The Engine Setup Wizard has some preset tables for this.
If the engine has standard camshafts the MAP at idle will be at least 30kPa.
Based on this, pick a value around 30kPa as the min value on the y-axis in the
VE table. You may still find that a lower pressure value is useful in order to
save fuel during coasting, which result in very low MAP readings.
If MAP is lower than the lowest point on the y-axis, NIRA i7x will use the
values from the bottom row. If the MAP value is between two points on the y-
axis, NIRA i7x will interpolate.