RX7 2RTR- 1308cc 1.3L Turbo FI (1989)
Wastegate: Description and Operation
Exhaust Flow W/Wastegate Open
The wastegate, which is integral with the turbine housing, allows exhaust gas to bypass the turbocharger when the maximum allowable boost pressure is
reached. This limits the turbocharger RPM and consequently limits boost pressure.
The wastegate is operated by a linkage rod connected to a pressure diaphragm. Under light load operating conditions (boost pressure less than maximum)
a spring holds the wastegate valve in the closed position. During boost, when manifold pressure reaches the maximum allowable pressure, boost pressure
in the diaphragm chamber works against the spring, opening the wastegate valve.
The wastegate actuator spring is very light, so that the wastegate will open at a low manifold pressure. A computer controlled solenoid valve is installed
in the manifold pressure line to the wastegate actuator. When the solenoid is energized, manifold pressure from the source is vented to the atmosphere,
reducing the pressure at the wastegate actuator. This allows the computer to regulate boost at a higher pressure than the wastegate alone would allow.
This also provides for a "fail safe" operation of the turbocharger. If the solenoid valve should fail, it will most likely fail in the closed position and boost
pressure will be regulated mechanically by the wastegate, at a less than maximum pressure level.
