Turbocharger: Description and Operation

SYSTEM DESCRIPTION

Fig. 73 Intake air system. Turbo:

Some 1987-88 RX-7 models are equipped with a dual chamber scroll turbocharger. In this turbocharger design, the primary and secondary chambers are separated by an integrally cast wall, with an intake vacuum-activated valve spring serving as a gate to open or close the secondary chamber. At low engine speeds, the smaller primary chamber concentrates exhaust gases and increases their velocity. This results in a significant improvement in throttle response and engine torque. At engine speeds above 2500 RPM or under certain load conditions, the larger secondary chamber opens, directing additional exhaust gases across the entire face of the turbine blades, providing increased engine horsepower and RPM. An air-to-air intercooler is positioned directly above the engine plenum chamber to cool incoming pressurized air.

HOT START ASSIST SYSTEM

Fig. 75 Hot start assist system. Turbo:

This system helps prevent excessive cranking and hard starting after hot soak.