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It was probably 25 years ago when I first listened to an injector and experienced DFCO.
The car was an early fuel injected Datsun 280 Z. They started using FI in 1975, under license from Bosch. You could hear DFCO with a automotive stethoscope while revving the engine with the car sitting in front of the main door to my shop.
Basically Nissan used DFCO in their first FI cars to eliminate the unburned hydrocarbon spike when the throttle was released. The throttle position sensor had to be at idle position and any imput would automatically stop DFCO. The early Z cars (75-78) had no catalytic converters in the Federal versions, while California versions had converters. My 76 even had no EGR system from the factory while still passing Federal emissions.
I believe the initial purpose of DFCO was to eliminate the air injection systems that were necessary to burn the otherwise unburned fuel when the throttle was released without DFCO. They even had fuel shutoff in some of the last carbureted versions of Nissan-Datsuns of the same era as the first FI Z cars. DFCO accomplished the same function as air injection had done before, but with the added advantage of 0 fuel delivery.
regards
Mech
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