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The recent availability of fast response (< 1.0 seconds) exhaust gas temperature sensors for exhaust gas temperature measurement enables a new method for closed loop feedback engine control in small engines and other non-stoichiometric applications (V-8 marine fuel injected engines for example). Conventional closed loop stoichiometric A/F control with traditional switching type oxygen sensors is often not applicable because these engines rarely if ever operate at stoichiometric A/F ratios. Richer A/F ratio control is necessary for maximum power and combustion temperature cooling. Wide range UEGO A/F sensors are an alternate solution but the cost of these sensors may be too high. Additionally, the very short exhaust systems found on many small engines can allow ambient air to back flow into the exhaust due to pressure pulsations and corrupt the signal from an oxygen concentration type sensor.

An Electronic Fuel Injection system has been developed for utility engines which will reduce exhaust emissions and give greater control of the Air/Fuel ratio compared to the standard carburetor. Standard automotive components were used when possible. The Electronic Fuel Injection system is a port fuel injected design using a bottom feed fuel injector which sprays directly on the intake valve. The engine speed/position, throttle position, air intake temperature and cylinder head temperature are measured and fed into the Electronic Control Unit. Look-up tables are used to determine the injection duration time during starting, warm-up, acceleration and normal operating conditions. Normal operating conditions are conditions the engine would encounter during actual use such as idle to governored rpm, no-load to full load, ambient temperature ranges from -40°C to 55°C, and any combination of the above.