Engine fuel mixture control system

In an internal combustion engine having a fuel supply connected to said engine by a fuel line, a valve means connected in said fuel line for regulating the fuel flow to said engine, and an air intake means, said air mixing with said fuel to provide a combustible charge for the engine, a fuel mixture control system comprises:

• a fuel flow meter connected in said fuel line, said fuel flow meter providing an output signal representative of the fluid flow rate through the fuel line;
• an air flow meter connected to the air intake means, said air flow meter providing an output signal representative of the air flow rate into the engine;
• proportioning means connected to the outputs from said flow meters for providing an output signal representative of the fuel/air ratio for the engine;
• a reference fuel/air ratio means for providing an output signal representative of the optimum engine fuel/air ratio for a given engine condition;
• means for comparing said reference means output with said proportioning means output and producing an output signal representative of the difference therebetween;
• and
• means responsive to said comparing means output signal for controlling said fuel valve means so that said comparing means output attains said reference output
• wherein said reference means further comprises a variable fuel/air reference means having its output connected to the comparing means, said variable reference means being switchable between a high level in which the output to the comparing means is representative of maximum permissible engine fuel/air ratio and a low level in which the output to the comparing means is representative of the minimum permissible engine fuel/air ratio, and sensor means having an output and responsive to a parameter representative of engine performance, first detector means for determining the slope of said engine performance parameter, second detector means for determining the slope of the engine fuel/air ratio, said first and second detector means having outputs connected to and controlling the level of the variable reference means, and means for disabling said responsive means when the first detector means output is substantially zero.