RX7 2RTR-1308cc 1.3L MFI (1991)
Intake Manifold: Description and Operation
Mazda RX-7 engines not equipped with a turbocharger have a special intake manifold assembly designed to improve engine performance. Mazda calls
this system the "VARIABLE DYNAMIC EFFECT INTAKE SYSTEM" (VDI for short). The system is designed to take advantage of oscillations inside
the intake manifold, created by the opening and closing of the intake ports, to improve volumetric efficiency especially at high engine speeds.
VDI System Manifold Assembly
The intake manifold is constructed in three sections. The lower section, simply referred to as the intake manifold, feeds the intake air charge into the
rotor housings. The middle section, called the "EXTEN" manifold (probably short for "extension" manifold), is where the dynamic effect takes place.
The upper section, referred to as the dynamic chamber or common chamber, is where the intake air enters the manifold assembly from the throttle body
before being separated into the individual manifold passages.
Variable Dynamic Effect Intake (VDI) System
