Fuel Map Auto Fill

Overview

The Fuel Map Auto Fill function generates an initial base fuel calibration using the engine, injector and fuel parameters entered by the user.

The calculated fuel map is intended to provide a technically reasonable starting point for engine setup and calibration. It is not intended to replace final engine tuning.

The calculation estimates engine volumetric efficiency (VE) according to the selected engine and camshaft characteristics, engine speed and manifold pressure. The resulting estimated air mass is combined with the target Lambda map, fuel properties and injector characteristics to calculate the required injection time.

Warning: The accuracy of the generated fuel map depends directly on the accuracy of the information entered. Always verify the resulting calibration before operating the engine under significant load or at high engine speed.

IMPORTANT – Injector Dead Time Calibration:  The injector dead time (latency) calibration must be correctly configured before using the Fuel Map Auto Fill function. The Auto Fill calculation determines the required net injector opening time based on the calculated fuel mass and injector flow rate; injector dead time compensation is handled separately by the ECU. Incorrect dead time values can therefore cause systematic fuelling errors, particularly at low load and short injection pulse widths, and may also cause fuelling to vary with battery voltage. Always verify the injector dead time calibration for the injectors and fuel pressure being used before relying on the generated fuel map. 

Engine Parameters

Bore
Enter the engine cylinder bore in millimetres.

Stroke
Enter the crankshaft stroke in millimetres.

Number of Cylinders
Enter the total number of engine cylinders.

Engine Displacement
The total engine displacement is calculated automatically from bore, stroke and number of cylinders. This value is displayed for reference and cannot be edited directly.

Maximum RPM
Enter the maximum engine speed for the intended calibration.
This value is also used to define the upper operating range of the calculated VE curve.

Peak Torque RPM
Enter the approximate engine speed at which maximum torque occurs.

This parameter has a significant influence on the shape of the calculated VE curve and should be entered as accurately as possible.

Peak Power RPM
Enter the approximate engine speed at which maximum engine power occurs.
Peak Power RPM must be lower than Maximum RPM and higher than Peak Torque RPM.

Low Power Bandwidth
Defines the approximate RPM range over which volumetric efficiency rises towards the peak torque region.

This parameter influences the shape of the VE curve below peak torque and can be used to represent engines with different low-speed characteristics.

Engine Configuration

Engine Type

Select the option that best represents the overall level of engine preparation:

• Standard Road — standard or lightly modified production engines.
• Fast Road — moderately modified road engines with improved breathing and performance.
• Performance — extensively modified high-performance engines.
• Motorsport — competition engines with high volumetric efficiency and a more aggressive operating characteristic.

The selected engine type primarily determines the expected minimum and maximum volumetric efficiency range.

Camshaft Type

Select the camshaft configuration that most closely represents the engine:

• Standard — production or near-production camshaft.
• Mild — mild performance camshaft suitable for road use.
• Performance — higher-duration/lift performance camshaft.
• Race — competition-oriented camshaft with stronger high-RPM characteristics and reduced low-speed efficiency.

The camshaft selection affects both the RPM-dependent VE curve and the VE response to manifold pressure.

Multi-Valve Cylinder Head

Enable this option for engines using more than two valves per cylinder.
The calculated VE characteristic is adjusted to represent the typical breathing behaviour of a multi-valve cylinder head, including its different low- and high-speed characteristics.

Turbocharged

Enable this option when calibrating a turbocharged engine.
A turbo-specific VE characteristic is applied around the peak torque and peak power regions. Manifold pressure itself is still taken into account separately by the fuel calculation.

Injector Parameters

Base Injector Flow

Enter the nominal injector flow rate in cc/min.

Use the flow rating specified at the injector's reference differential pressure.

Injector Reference Pressure

Enter the differential fuel pressure, in kPa, at which the injector flow rating was specified.

For example, an injector specified as:

500 cc/min @ 300 kPa

should be entered as:

Base Injector Flow = 500 cc/min
Injector Reference Pressure = 300 kPa

Injector Actual Pressure

Enter the actual differential pressure across the injector, in kPa.

Injector flow varies with the square root of the pressure ratio. Therefore, doubling fuel pressure does not double injector flow.

For example:

500 cc/min @ 300 kPa

operating at a differential pressure of:

600 kPa

produces approximately:

707 cc/min

and not 1000 cc/min.

Corrected Injector Flow

The effective injector flow at the entered operating pressure is calculated automatically and displayed for reference.

For fuel systems using a manifold-referenced 1:1 pressure regulator, remember that the relevant value is the pressure differential across the injector, not simply the measured fuel rail pressure.

Fuel Parameters

Fuel Stoichiometric AFR

Enter the stoichiometric air/fuel ratio of the fuel being used.

For conventional gasoline, a typical value is approximately:

14.7 : 1

Different fuels, including ethanol blends and racing fuels, may require substantially different values. Use the correct value for the actual fuel.

Fuel Density

Enter the fuel density in kg/L.

For conventional gasoline, a typical starting value is approximately:

0.745 kg/L

Use the actual fuel specification whenever available.

Reference Air Temperature

Enter the reference intake air temperature used for the initial air-mass calculation.

A typical reference value is 20 °C

The Auto Fill calculation uses this temperature when estimating the mass of air entering each cylinder.

Calculated VE Graphs

Calculated VE @ 100 kPa

This graph displays the estimated volumetric efficiency versus engine speed at 100 kPa manifold pressure.

Use the graph to verify that the calculated VE characteristic is reasonable for the engine configuration before generating the fuel map.

Changes to engine type, camshaft type, RPM characteristics, multi-valve configuration and turbocharger selection are reflected in the calculated curve.

Calculated VE vs MAP Correction

This graph shows the correction applied to volumetric efficiency as a function of manifold absolute pressure.

The shape of this curve is influenced by the selected engine/camshaft characteristics and represents the expected change in cylinder filling at different engine loads.

Lambda Target

The Auto Fill function uses the existing Lambda Target Map when calculating the required fuel quantity.

Because the Lambda map and fuel map may use different RPM and load breakpoints, the required Lambda target is calculated by interpolation between the surrounding Lambda map cells.

It is therefore important to configure and verify the Lambda Target Map before generating the fuel map.

An incorrect Lambda target will directly affect the calculated fuel quantity.

Generating the Fuel Map

After entering all engine, injector and fuel information:

1. Check that the calculated engine displacement is correct.
2. Check that the corrected injector flow is reasonable.
3. Review the calculated VE curve.
4. Review the VE vs MAP correction curve.
5. Verify the existing Lambda Target Map.
6. Press Calculate to generate the base fuel map.

Press Abort to close the Auto Fill window without generating the map.

The Auto Fill function uses the current RPM and load breakpoints of the active fuel map. It does not require the fuel map to use its maximum available dimensions.

After Auto Fill

The generated map should be treated as an initial calibration only. To confirm the generated map and store in the Ecu you have to press F4.

Before operating the engine under significant load:

• Check the complete generated fuel map for unexpected values or discontinuities.
• Verify that injector specifications and fuel pressure are correct.
• Verify the Lambda Target Map.
• Confirm fuel pressure and injector operation on the vehicle.
• Monitor Lambda/AFR during initial engine operation.
• Progressively validate the calibration through the RPM and load range.
• Perform final calibration using appropriate measurement equipment and normal engine tuning procedures.

Closed-loop Lambda control should not be considered a substitute for a correctly calibrated base fuel map.

Safety Notice

Fuel Map Auto Fill provides an estimated starting calibration based on the parameters entered by the user. The generated values are dependent on the accuracy of the engine, injector, fuel and operating data supplied.

Always review and validate the generated fuel map before operating the engine. Final calibration should be performed by a competent operator using appropriate Lambda monitoring, engine instrumentation and tuning procedures. Incorrect fuel calibration may result in poor engine operation or engine damage.

NOTE: This currently only works for Speed Density configurations. Alpha-N will follow.

Here's a short video of this in action: