The development and preliminary results of a low cost electronic fuel injection (EFI) system for one and two cylinder 4-cycle gasoline engines is described. The feasibility of reducing system cost by minimizing the number of sensors is explored. The objective is to use only the following signals to determine the operational state of the engine:
Another objective in the on-going development is to maintain the performance enhancements that EFI offers over carbureted engines: cold starting, fuel economy, and reduced emissions.
Special focus is applied to the creation and analysis of a load signal that is related to the torque produced by the engine. Constrained by certain conditions, the load signal is related to the air charge entering the cylinder. The load signal, along with the engine speed signal, provides a basis for a fueling look-up table. The fuel table gives the engine manufacturer greater freedom in tailoring the air/ fuel ratio (A/F) at different operating points.
A description is given for how load is calculated from the periodic speed fluctuations between the power revolution and non-power revolution. The algorithms and required signal processing are described to achieve an accurate measure of this signal. A high-pass filter is used on the speed samples to reduce noise before the calculation of the load signal.
Issues pertaining to throttle transitions, application load transitions, application inertia effects and inertia compensation are described.
Fuel delivery system cost reduction is discussed in future work.