• + TwoStage turbo system sets the standard
  • + Engineering partnership delivers innovative compact architecture

World-leading and World-class

Posted 09.09.2011

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The world’s first TwoStage Serial boosting system developed for a V6 turbodiesel engine is helping the recently launched Audi A7 Sportback set benchmark performance in its class. The turbo architecture designed by the engineering team at Honeywell in partnership with Audi is unique for the power, torque and transient response it helps deliver for the auto manufacturer’s state-of-the-art high performance 313hp 3.0L diesel engine. With up to 35% increased engine power and up to 10% improved fuel economy, this downsized engine, with its 30% displacement reduction, illustrates the benefits of a TwoStage Serial turbocharged engine.

Audi A7Audi’s head of diesel engine development, Richard Bauder, was recently quoted as saying “with the new V6 TDI turbo we now have an optimum engine family with efficiency-and performance-oriented variants.”

Honeywell TwoStage Serial turbo systems feature a high pressure VNT™ turbo that maximizes low end response coupled to a second low pressure turbo that kicks in at a set engine speed to deliver high-end output. It’s an architecture widely acknowledged for its ability to provide auto manufacturers with the ultimate driveability.

High pressure (HP) turbo
The performance of the HP turbocharger plays a vital role in transient response and part-load emissions of engines equipped with a TwoStage Serial system. The use of variable-geometry architecture optimizes turbine operating conditions to provide exactly the right boost performance.

In addition, the HP compressor stage is designed to operate with high efficiency, minimizing energy requirements on the HP turbine, while possessing the wide operating-range needed to facilitate transition between TwoStage -mode and mono-stage mode.

Low pressure (LP) turbo
Aerodynamic optimization of the LP turbocharger is key to TwoStage performance, and in selecting the right low pressure turbo for this application, Honeywell engineers have taken the following into consideration:  compressor sizing to deliver maximum power, turbine design to minimize engine backpressure, and compressor and turbine size and inertia to meet packaging and transient response requirements.

twostage-turboTurbine bypass valve
Beyond the selection and optimization of the HP and LP turbochargers for best aerodynamics, the performance characteristics of the turbine bypass valve are no-less essential. The Honeywell bypass valve was designed to meet these key requirements: low-leakage, low-losses and high-temperature capability.

Packaging
Honeywell engineers were tasked to come up with compact designs for both HP and LP turbochargers. Again, according to Bauder, “the low-pressure turbo is positioned transversally; the high-pressure turbo is mounted longitudinally.” Despite the daunting challenge, Honeywell engineers succeeded in, through continuous back-and-forth iterations between package-designer, FEA analysis, and castability optimization, integrating many pipes into a packageable design that is reliable and manufacturing-friendly.

As a result of the close collaboration between the engineering teams, the Honeywell TwoStage turbo system is making a significant contribution to the very high-performance EU5 V6 3.0L Audi engine…and helping the model lead the way in its class.

(A joint paper will be presented by Audi and Honeywell Turbo Technologies at the Turbocharger Conference in Dresden in September 2011)