Variable Geometry Turbocharger

WARNING: This page is about a different car, the 2018 Land Rover Discovery and 2017 Land Rover Discovery. However, it is still accessible from the selected car via links, so may be relevant.

The turbine wheel of the Variable Geometry Turbocharger (VGT) uses the engine exhaust gases to drive the compressor wheel. The compressor wheel draws in fresh air which is compressed and delivered through a charge air cooler to the throttle body.

By turbocharging the engine, the pressure and density of the air entering the cylinders is increased, and therefore so is the amount of oxygen. This enables a greater quantity of fuel to be injected, thus increasing the engine's power output, improving fuel consumption and the ability to maintain power at higher altitudes.

The charge air cooler (air to water type) is used to increase the density of air as it flows from the VGT compressor to the intake manifold. Compression of the charge air by the VGT raises the temperature of the air. This generation of heat further decreases the charge air density, and consequently less oxygen is able to enter the cylinders, reducing the engine power. To overcome this, the air is routed through the charge air cooler before it enters the engine, so the temperature is reduced by transferring the heat to atmosphere. Cooling of the intake air also helps to reduce engine emissions by limiting nitrogen oxides (NOx) production.

The VGT allows the optimum inlet geometry (inlet area and flow angle) to be used over a wide range of engine operating conditions. This allows a rapid speed of response and higher charge air pressures at low engine speeds. The variable vane angle determines both the inlet area as well as the flow angle, as controlled by the Powertrain Control Module (PCM) via the VGT vane actuator. The variable vanes allow efficient use of the exhaust gas energy which in turn improves VGT and engine efficiency.