Toyota Supra 1990 Manual page 137

TURBOCHARGER SYSTEM - Description
TC-3
Actuator
Waste Gate
Valve
Operation of the Turbocharger
Exhaust gas acts on the turbine wheel inside the
turbine housing, causing it to revolve. When the tur-
bine revolves, the impeller wheel which is located
on the same shaft also revolves, compressing the
intake air which has passed through the air flow
meter from the air cleaner. When expelled from the
compressor housing the compressed air is supplied
to the cylinders. When the engine speed increases,
the exhaust gas volume increases and the turbine
wheel revolutions increase (approx. 20,000 rpm -
110,000 rpm), thus the turbocharged air pressure
grows greater and engine output increases.
Waste Gate Valve
Although on the one hand high output is achieved
by turbocharging, if the turbocharged air pressure
becomes too high, knocking occurs and on the con-
trary, a reduction in engine output is caused. If the
turbocharged air pressure exceeds the prescribed
air pressure, the flow of exhaust gas bypasses the
turbine, controlling turbine wheel revolutions and
turbocharge air pressure. This by-pass valve which
controls the quantity of exhaust gas flowing to the
turbine is called the waste gate valve.
When the supercharged air pressure exceeds the
prescribed pressure, the actuator operates, the
waste gate valve opens and part of the exhaust gas
by-passes the turbine. This causes a drop in the tur-
bine revolution rate and controls the supercharged
air within the prescribed limits.
Intercooler
Air
Cleaner
TC0011
The intercooler cools the turbocharged air (intake
air) put out by the turbocharger, thereby increas-
ing the air density. As the air intake efficiency in-
creases, the gas temperature in the combustion
chamber falls and the occurrence of knocking is
suppressed giving an increases engine output.
The Supra 7M-GTE intercooler is an air cooling
type located at the front of the vehicle, utilizing the
vehicle windstream to cool the turbocharged air.