Ported EGR Valve

With this system, amount of exhaust gas admitted into intake manifold depends on vacuum signal (ported vacuum), controlled by throttle position.

When throttle is closed (at idle or deceleration), there is no vacuum signal to EGR valve because EGR vacuum port is above the closed throttle valve. As the throttle valve is opened, ported vacuum is applied to the top of the diaphragm which overcomes spring pressure and opens the valve in the exhaust gas port. Exhaust gas then is admitted into the intake manifold.