Garret announces two-stage VNT boosting system on a 6 cylinder diesel engine

12 May 2021

Garrett provided some more insight on their two-stage turbocharger systems with variable nozzle/geometry turbines (VNT/VGT) at both the high and low-pressure stages, developed for BMW 6 cylinder diesel engines.

The BMW 3.0-liter I6 engine with the dual VGT system—in combination with a 48 V starter-generator—can produce 250 kW (340 hp) of power and 700 Nm (516 lb-ft) of torque, while meeting Euro 6d emission standards and achieving very good highway and urban fuel efficiency ratings.

The dual VGT system was introduced in 2020 in BMW 6 cylinder diesel engines for the X6 40d, X5 40d, and 340d models [4705]. It is based on the two-stage turbocharger system—also supplied by Garret (formerly Honeywell)—that debuted in 2015 in BMW 4 cylinder diesel engines for the 125d, X1 25d, and 225d.

The features of the 6 cylinder engine boost system include:

• New Integrated Manifold—The system is integrated with a seven port exhaust manifold, where six ports serve the engine cylinders and one the EGR.
• New Bypass Valve—the addition of an electronically actuated turbine bypass valve in conjunction with two VNT actuators improves engine responsiveness, especially when the engine transitions from single-stage to two-stage operation.
• VNT on High Pressure Turbine—The VNT technology on the high-pressure side allows to better control turbo boost at low-engine rpm and also help transition the second low-pressure stage at now higher engine speeds (2,250 rpm), which helps the second stage focus on higher-efficiency operating ranges.
• Water-Cooled Compressor—The water-cooled Garrett compressor enables higher EGR rates to reduce NOx formation. This allows the engine to achieve high power and torque outputs, while meeting Euro 6d emission standards.

Source: Garret