MoTeC M1 Software Tutorial: Changing Fuel Type
To do it’s job properly the M1 ECU needs to know the properties of the particular fuel you are running.
This allows the ECU to understand how much fuel is required to achieve a certain mixture aim, as well as how fuel volume relates to fuel mass.
afterall, it is the mass of air and fuel we are interested in, not the volume.
What this means is that entering the fuel properties correctly into the M1 ECU is critical to the accuracy of your tune.
We have already discussed these parameters during our initial setup worksheets, however in this section we will discuss what parameters need to be addressed if you are changing fuel types.
There are three parameters that we need to address and these can be found in the ‘Engine Details’ worksheet in the ‘Initial Setup’ workbook.
First of all we need to adjust the ‘Stoichiometric Ratio’ to suit the specific fuel.
This parameter describes the mass of fuel that is required to match a certain mass of air for theoretically ideal combustion.
The stoichiometric AFR varies widely between different fuels and failing to adjust this correctly can result in the engine running too rich or too lean.
Next we have the ‘Fuel Density Reference’ and the ‘Fuel Density Temperature Coefficient’ which describe how the fuel volume relates to fuel mass, and how this fuel mass will vary with changes in fuel temperature.
Values for common fuels are provided for reference in the context specific help, and if you are using a specially blended race fuel, this information should be available from the manufacturer.
Provided you have changed these parameters to suit your new fuel, the engine should run with the same measured lambda values as it did previously.
You may still need to adjust your Aim Mixture and Ignition tables to take full advantage of a different fuel though.