As we mentioned last month, the OzTrip Computer can most easily be used in cars with standard electronic fuel injection (EFI) systems. The computer uses data already available within the EFI system.

With modifications (involving the use of an optional PC board) it can also be used in vehicles with carburettors or non-standard EFI. This entails the fitting of a fuel flow sensor – not a difficult job at all.

EFI operation

The OzTrip Car Computer is easy to build, easy to fit and easy to calibrate. The best part: you save money!

The OzTrip Computer measures the fuel flow of an EFI engine by measuring the time one injector is open.

The main components of the fuel delivery system in an EFI engine include the fuel pump, pressure regulator, fuel rail and fuel injector valve.

The fuel injectors are under the control of the engine management computer (EMC). This adjusts the time the injector is open and therefore the amount of fuel sprayed into the cylinders, according to the speed of the engine and the load on it, attempting to achieve maximum efficiency at all times.

The pressure in the fuel rail, which feeds the injectors, is kept constant by the pressure regulator. Because of this, the fuel flow through each injector can be assumed to be the same (on average) so we only need to measure one injector to determine the total fuel flow.

The fuel flow is directly proportional to the injector open time and by measuring the injector open time we can calculate the fuel consumption.