On-Off EGR System (Turbo)
Exhaust gases (from exhaust port of number 2 cylinder) are routed through the cylinder head, and then through a steel pipe, to EGR valve in inlet manifold. See Fig 1 .
Opening of the EGR valve, when coolant temperature is below 112°F (43°C), is regulated by a vacuum port in throttle valve housing. At idle, vacuum is not applied to the port, resulting in a closed system.
When engine speed reaches 1900 RPM, vacuum is applied to the port resulting in a full signal to (and a full opening of) the EGR valve. A special size orifice, depending of type of transmission used, allows only a certain amount of exhaust gas to reach EGR valve.