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Turbo pressure control

Turbo pressure control


The engine is fitted with a Garret 15 VNT (Variable Nozzle Turbine) type turbo. This turbo has no wastegate and instead is controlled by a set of guide rails on the exhaust side of the turbo.

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This controls the turbo so that on low gas flow, the turbo speed increases and hence the boost pressure. This means a higher engine torque even at low engine speed. At higher gas flow, the turbo unit speed is reduced to avoid over-revving of the turbo but still give the desired boost pressure.

The turbo pressure, which is dependent on the engine speed and load, is monitored continuously via a pressure sensor mounted on the intake manifold. The vacuum box which controls the guide rails is larger than in previous turbo designs. The vacuum pump has a bigger connection than before to ensure that the vacuum box has adequate vacuum.


• The engine develops more torque at low speed.

• As the working temperature of the turbo can be kept down, the compression of the air to the cylinders is improved, which increases power.

• The turbo responds more quickly to the desired torque which means improved drivability.

• The engine consumes less fuel and has reduced emissions.