Operation - Toyota 3S-GTE Repair Manual

E6-8° ENGINE — TURBOCHARGER SYSTEM
OPERATION
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Turbine Wheel Impeller Wheel
Air Cleaner
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Exhaust gas acts on the turbine wheel inside the turbine housing, causing it to rotate. The
impeller, located on the turbine shaft, thus rotates and compresses the intake air which has
passed through the air cleaner. This high pressure air than passes into the cylinders for
combustion.
As the engine speed increases, the exhaust gas volume increases causing the turbine wheel
speed to increase up to a maximum of approximately 120,000 rpm. The consequent increase in
the impeller rpm increases the pressure of the intake air. which when accurately combined with
an appropriate quantity of fuel, increases engine power.
Waste Gate Valve
Although turbocharging increases engine power, if the turbocharged air pressure becomes too
high, knocking occurs which reduces engine power. If the intake air pressure exceeds a pre-
determined valve, the waste gate valve causes the exhaust gas to bypass the turbine. This
reduces the speed of the turbine, thus reducing the intake air pressure.
lntercooler
The intercooler cools the turbocharged intake air, thereby increasing the air density. With a
redustion in intake air temperature, the reduced combustion temperature suppresses the occur-
rence of knocking and allows full engine power to be realized.