The app supports multiple fuel tanks which can be defined within the same car profile.
This is especially useful for cars that utilize multiple fuel system types, such as gasoline and LPG fuel systems (applicable to other fuel system types).
However, this poses a problem as to what fuel tank should be used for current statistical calculations in the app. In case of a retrofitted LPG system, the additional ECU managing LPG delivery and the OEM ECU do not communicate with each other, thus it's not possible to directly tell what fuel type / tank is being used at a time.
To work around this issue, the app uses additional usage conditions, configurable user preferences, that are available as soon as the user adds two or more fuel tanks, thus allowing the user to define trigger conditions that enable the app to indirectly determine (from other available OBD parameters) which type fuel and fuel tank is used.
In case of a LPG system, the ECU is programmed to switch on LPG delivery as soon as a certain coolant temperature threshold is reached (~45 °C).
When the LPG delivery switches on, usually the overall fuel trim starts to change significantly in order to maintain a proper stoichiometric coefficient of the fuel mixture, measured by the oxygen sensor.
These parameters can be used as inputs for the usage conditions, for each defined fuel tank.
Usage conditions configuration
The gasoline tank can be viewed as a primary tank, which is used by default, thus it does not require any special "usage conditions" to be defined.
The LPG tank's "usage conditions" can contain either one condition, for example "use tank if engine coolant temperature is USER_VALUE °C/F", or multiple conditions for higher deterministic accuracy, for example
"use tank if engine coolant temperature is above USER_VALUE °C/F" AND "fuel trim is above USER_VALUE %".
To add "usage conditions", navigate to each fuel tank's preferences screen and open the "usage conditions" view, where you can add, remove and edit conditions.
Configuration example
The values shown in this example may not be applicable to all cases. In order to determine proper threshold values for the conditions, analyze the "Short Term Fuel Trim" and "Long Term Fuel Trim" parameters when the LPG fuel is used and compare it with the values when the gasoline fuel is used.
Tips
you can define and combine multiple condition blocks using logical operators (AND, OR)
within a condition block you can define multiple parameters, which can be combined using simple arithmetic operations (add, subtract, multiply, divide)
