1982, 3-Way Closed Loop Fuel Injection (Throttle Body type)
This application of 3-way closed loop single bore throttle body fuel injection (TBI/EFI) replacing carburetion, was on the full volume of 4 cylinder Pontiac “Iron Duke” engines. The microprocessor based fuel controller also included scheduling for spark timing, exhaust gas recirculation (EGR) and idle speed control.
As in 1979’s first introduction at Cadillac, the continuing motivation to change from carburetion to fuel injection was to provide improved driveability over the wide range of conditions of the automotive environment: temperature, altitude, humidity and vehicle acceleration/deceleration, while meeting the ever lowering HC, CO and NOX exhaust emission standards.
This meant that over-rich calibrations to hide variations in carburetor metering had to be eliminated, particularly during cold starts. It was during this period that carburetor driveability complaints increased, causing customer dissatisfaction. The carburetor had reached its limit in providing the smooth and expected driveability demanded by customers in this decreasing emissions environment.
Carburetors contained up to eight individually calibrated fuel metering circuits, all sensitive to small changes in venture differential pressure, metering orifices, fuel properties and contaminants.
Fuel injectors, on the other hand, with one metering orifice, operate at a significantly higher differential fuel pressure. Thus, EFI in concert with its sensors and repeatable digital microprocessor controller could deliver a more consistent open loop fuel to the engine under its wide range of starting and operating conditions. This tight open loop capability resulted in improved closed loop air/fuel control, enabling the exhaust stream constituents to be efficiently equilibrated with a three-way single bed oxidizing/reducing converter.
Note: In 1982, GM’s Delco Electronics had approximately half of the world’s electronics silicon dedicated to manufacturing its automotive products. GM became the world’s largest manufacturer of computers that year, producing some 25,000 units a day.
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