ENGINE DECELERATION INTAKE AIR FLOW REDUCTION AND FUEL SHUT-OFF CONTROL

In an automotive type engine having an air bypass valve controlling a portion of the air flow to the engine, decelerations are controlled in a manner to minimize or eliminate the conventional large feedback negative torque impulse to the operator usually experienced when fuel is shut off. The air bypass valve is closed down, in response to correct decel conditions, to an air flow level below that scheduled to establish the normal idle speed condition. The positive engine combustion torque is decreased so that the magnitude of the ratio between it and the engine negative torque becomes small. Immediately following fuel shut-off, the bypass valve is reopened to return the air flow to that level establishing the set idle speed condition upon resumption of fuel flow.