Electronically-controlled fuel injection system for internal combustion engine having odd numbers of cylinders

An electronically-controlled fuel injection system for an internal combustion engine having an odd number of cylinders, in which the quantity of fuel supplied to the engine cylinders is regulated by the duration of pulses of a fuel injection pulse signal applied to solenoid-operated fuel injection valves, and two fuel injection pulses are generated in each operating cycle of the engine in synchronism with the revolution of the engine, said system comprising:

• a waveform reshaping circuit adapted to be connected to an ignition unit of the engine for reshaping the waveform of an ignition signal upon receipt from said ignition unit thereby providing an output pulse signal subjected to the waveform reshaping;
• a frequency doubler circuit connected to said waveform reshaping circuit for doubling the frequency of the output pulse signal of said waveform reshaping circuit thereby generating a frequency-doubled output pulse signal;
• a frequency divider circuit connected to said frequency doubler circuit for dividing the frequency of the output pulse signal of said frequency doubler circuit by the number of engine cylinders thereby providing a frequency-divided output pulse signal;
• and
• computing means connected to said frequency divider circuit for generating said two fuel injection pulses in synchronism with the output pulse signal of said frequency divider circuit.