EGR Valve

On 2002, 530i and 3.0Si, a dual diaphragm valve operates in 2 stages. When vacuum is about 3. in Hg, vacuum is applied to upper diaphragm to partially lift EGR valve from seat allowing a small amount of exhaust gas flow. The second stage of EGR valve is controlled by a vacuum control valve which senses absolute pressure in intake manifold. When second stage is opened, EGR vale is lifted completely off its seat allowing full exhaust gas recirculation.

On 630CSi, 633CSi and 733i, the EGR valve is controlled by vacuum inputs from the pressure transmitter and the electromagnetic switching valve or thermo valve. The EGR valve consists of two diaphragms which allows precise control of the quantity of exhaust gas recirculation. The upper diaphragm is sued to close the valve completely, thus stopping the flow of exhaust gas. The lower diaphragm determines the quantity of exhaust gas recirculation.