Variable vane, or variable geometry, turbo chargers are typically used in conjunction with diesel engines or high performance gasoline engines. Variable vane turbo chargers not only increase engine power and torque (turning moment), but also lower fuel consumption and emissions.
When the load on an engine is low, the vanes on the turbo charger remain closed. Little exhaust causes flows across the turbine impeller, or rotor, producing little turbo charging effect.
When the load on an engine is high, the vanes on the turbo charger are opened by a servomechanism, or actuator, controlled by an electronic control unit (ECU), which monitors engine speed and load using sensors. This allows a stream of exhaust gases to flow over the impeller.
The impeller rotates at high speed, driving a compressor and creating a high boost pressure in the inlet manifold. The inlet manifold is the collection of pipes that carries vaporised fuel from the carburettor to the engine cylinders.
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