Escort L4-98 1.6L SOHC VIN 5 FI (1985)
Fig. 40 Venturi vacuum amplifier
A Venturi Vacuum Amplifier, Fig. 40, uses a weak venturi-vacuum signal to produce a strong intake manifold vacuum to operate the EGR valve,
thereby achieving an accurate, repeatable and almost exact proportion between venturi airflow and EGR flow. This assists in controlling oxides of
nitrogen with minimal sacrifice in driveability.
There are three basic types of EGR valves: the ported type, the back pressure type and the electronic-sonic type.
The electronic-sonic type valve is used with the EEC system. Information on this valve can be found in the ``EEC'' section of this chapter.
Fig. 41 Ported type EGR valves
Ported type valves, Fig. 41, may be of the poppet or tapered stem design and can have base or side entry. The two passages connecting the exhaust
system to intake manifold are blocked by a valve which is opened by vacuum and closed by spring pressure.
