What is a turbocharger? A turbocharger is simply an exhaust-driven component designed to increase
the engine's power output by way of forced induction. The concept is this: the more oxygen
that can be squeezed into the combustion chamber, equals more fuel that can be burned as well. When
ignited, these increased combustion forces are much more than a naturally aspirated engine.
The turbocharger is driven by hot exhaust gases directed from the exhaust manifold driving a
turbine located in the center section of the turbo. The rotation of the turbine and compressor
wheels force air into the intake system. It is essential to understand that turbochargers require
a flow of hot exhaust gases, mainly the heat from those expanding gases, that produce the flow. The
original equipment turbocharging systems have a turbocharger, intercooler and a component that
controls the boost. The turbocharger consists of three sections: the compressor housing,
the center section and the turbine housing. The compressor housing is known as the cold side. It
houses the compressor wheel and is attached to the center housing and also the intake plenum.
The center section consists of the compressor wheel, and turbine shaft wheels. Bearings, oil
and coolant passages are all inside of here. The center section is also called the bearing housing.
Lastly, the turbine housing, also known as the hot side, it contains the turbine wheel, and on most
applications, an integrated wastegate. Naturally, air temperatures increase as they're compressed,
therefore, an intercooler is used to cool the air discharge from the compressor. This
radiator-style component can be water to air much like a radiator, or air to air,
where only ambient air passing over the fins cools the air passing through the intercooler.
Although forcing more air into the cylinders increases the volumetric efficiency of the engine,
and desirably increases its power, it is also necessary to control the boost pressure.
Since the turbocharger uses heat energy from the exhaust to produce boost, the more boost pressure
it produces, the more heat. It is essential that controls are in place to prevent excessive boost
pressure which can cause the turbo and engine to be damaged. Conversely, a deficiency in boost will
decrease the power output of the engine. Most systems employ a wastegate and a bypass valve
to control the system. Wastegate controls the boost pressure by redirecting exhaust gases
around the turbine wheel to bypass and maintain flow to the turbo. It uses a diaphragm attached
to an actuator rod that closes a valve. Most OEM wastegates, they're integrated into the turbo,
and some aftermarket applications use a remote design enabled with a larger diaphragm and better
materials. The wastegate is controlled by the amount of pressure the turbo is creating. This
pressure, derived from the intake manifold or compressor discharge, is called the wastegate
actuator signal. The valve opens once the wastegate actuator signal overcomes the
diaphragm spring. While the wastegate protects the vehicle from producing too much boost,
the bypass, or pressure release valve, sometimes known as the blow-off valve or a bob, releases or
displaces the boost pressure when the throttle is closed. These valves can either be vacuum or
electric solenoids. While all turbocharger systems are made up the same basic parts,
just as described, each vehicle application can have different diagnostic strategies
to test and confirm proper operation. Make sure you can refer to the vehicle service information
before attempting to repair or replace your turbocharger. Thank you for watching.
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