Fuel parameters

Top  Previous  Next

Fuel tables (MAP based systems)

Fuel tables are volumetric efficiency tables when using a speed-density system.  AFM based systems do not use these tables.




WOT lambda adjustment tables

WOT (wide open throttle) tables are used by the ECU to add fuel under high load conditions.  The tables are used when the ECU determines the engine is at WOT.  See Closed loop parameters on how to adjust the WOT determination parameters.


When using the tables it is assumed that the basic fuel injection quantity is set to give a stoichiometric air/fuel ratio, for both MAP and AFM based systems.  The WOT tables specify the lambda adjustment based on the assumption that the basic fuel injection quantity is stoichiometric.




Important note:  Do not use values above 12.50 (AF) or 0.85 (lambda), otherwise the ECU will always run closed loop.


Injector Size


Changing the current injector size will automatically compensate main fuel tables, cranking fuel and closed loop operation for the new injectors.  Note that the injector flow is nominally at 3 bar (43.5 psi).


Fuel Pressure


This compensates for fuel pressure if different from stock.  The injector test pressure values are the flow test pressures for both the stock fuel injectors and current fuel injectors.  Normally injectors are flowed at 3 bar, but different brands of injector may be flowed at different pressures.  In combination with the stock and current fuel pressure settings this compensates the main fuel tables, cranking fuel tables and closed loop operated for changes in fuel pressure and injector flow test pressure.


Fuel Trim


This allows compensation of both the main fuel tables (MAP based systems), AFM and cranking fuel tables.  Note that changing the injector size automatically performs the injector size compensation, and these settings normally do not need to be changed.


Injector Opening Time


This allows the injector opening time (or injector dead time) to be altered.  Normally the injector manufacturer will supply injector opening time figures.


Overrun Fuel Cut Delay


This is the delay between overrun conditions being met (throttle closed, rpm over about 1800 rpm) and the injectors shutting off.  A long delay gives 'rev hang' effects.  A short delay makes the vehicle jerky at light throttle.  Note that for 6 speed vehicles often the table only has 5 columns, in which case the 5th gear setting is used for both 5th and 6th gears.


Fuel Table Type


For some AFM calibrations it is possible to use a MAP (volumetric efficiency) lookup fuel tables.  In this case, the AFM is still required to be present but the AFM flow is not used to determine fuel.


It is also possible to use the AFM at low manifold pressures and the MAP at higher manifold pressures.  The 'Minimum pressure for speed/density' is the manifold pressure where the ECU will switch from AFM (mass flow) to MAP (speed/density).


AFM Fuel


With AFM vehicles the ECU calculates the injector duration from the mass of air per cylinder. This table converts from air mass to injector duration.


Individual cylinder fuel trim


Individual cylinder fuel trim allows different fuel to be delivered for each injector.  This table should only be adjusted if individual lambda probes are used to measure the air/fuel ratio for each cylinder.


Air temperature compensation




These tables adjust fuel by intake air temperature.  Three tables are used, based on the air flow rate into the intake manifold. Positive values add fuel; negative values reduce fuel.



This table adjusts the cranking (starting) fuel by intake air temperature. Positive values add fuel; negative values reduce fuel.


Coolant temperature compensation



These tables adjust fuel by coolant temperature.  Two tables are used - one for low load (below approx 40 kPa manifold pressure), and one for high load. Positive values add fuel; negative values reduce fuel.



This table adjusts the cranking (starting) fuel by coolant temperature.  Positive values add fuel; negative values reduce fuel.


Fuel Economy



For some models the ECU records the fuel used, which is then used to calculate the fuel economy.   To do this the ECU will subtract the injector opening time from the injector duration, then use a reference injector flow value to calculate the amount of fuel delivered.  These parameters are not supported for 'race' calibrations.

Injector flow for fuel economy

The reference fuel flow value used by the ECU. It may not be the same as the injector size, since different fuel pressures may be used for each measurement.

Injector flow for dash

The reference fuel flow value used by the dash for fuel economy display.