A proposed set of modifications, which, in combination with a mixture-Optimizer, enables a spark-ignition engine to accept air-fuel mixtures as lean as 22 - 23-1/2:1 without impairment of drivability, will permit the simultaneous reduction of all pollutant exhaust emissions, HC, CO, and NOx, to a very low level.
Under such circumstances, the true best economy mixture largely coincides with the mixture ratio that minimizes the exhaust emissions.
The mixture-Optimizer is a feedback type of electronic control device which automatically selects for a carburetor or fuel injection system the air-fuel ratio that yields the minimum fuel consumption for any given power output. For all driving conditions, other than idling and coasting, the minimum fuel consumption occurs at mixture ratios close to the borderline misfire limit. Therefore the mixture-Optimizer, by seeking these mixture ratios, tends to reduce all pollutant exhaust emissions that are under legal control. It also helps drivability by discouraging engine stalling.
The mechanism of the mixture-Optimizer is described, and results of simulated tests are presented.