Backpressure Variable Transducer Two Stage EGR Control System

To meet the challenging task of good vehicle driveability and fuel economy at the more stringent 1983 exhaust emission standards, the exhaust gas recirculation (EGR) must be controlled accurately at variable rates as a function of engine mass air flow under all vehicle operating conditions.

To achieve this objective, Ford Motor Company developed a new EGR control system referred to as Backpressure Variable Transducer (BVT), with two stages of operations. The first stage regulates EGR at a low and constant flow rate for light load and low speed operating conditions. The second stage provides high and variable rates of EGR for moderate to heavy load and high speed conditions. An exhaust gas backpressure input to BVT provides a signal proportional to engine mass air flow and the transducer calibration determines the operating stage. A closed loop feedback feature of the transducer maintains the required flow accuracy and compensates for any EGR valve functional deterioration. Description, theory of operation and test results are discussed on this paper.

The initial application of the BVT EGR control system is the 1983 1.6L CVH engines built to California and Federal Emission Standards.