The New 3.0-litre V6 TDI Engine in the Audi Q5

In 2003 a V6 TDI engine entered production for the Audi A8. Its high torque, power density and efficiency established a new milestone in passenger-car diesel technology. Now available in two displacements (2.7-litre and 3.0-litre), it has in the meantime been adopted for almost all the Volkswagen Group’s passenger-car models with longitudinally installed engine. Its power output, torque and maximum engine speed have been improved.

Audi Q5

Audi Q536

Aggregates | Diesel Engines

1 Increased-efficiency V6 Diesel Engine

The V6 TDI engine has been further opti-mised for use in the new Audi Q5: engine friction and internal flow losses have been reduced and the combustion process im-proved to enhance operating efficiency and in this way to render the engine more economical and give it better perform-ance characteristics. Equipped with a die-sel particulate filter (Catalysed Soot Filter – CSF), the V6 TDI outperforms the Euro 5 exhaust emission limits. In the Audi Q5 the version with a displacement of 3.0 li-tres and the new six-speed direct shift gearbox develops 176 kW at 4000 to 4400 rpm. Its maximum torque of 500 Nm is available over an engine-speed range from 1500 to 3000 rpm, Figure 1.

2 Chain Drives with Reduced Friction Losses

The new V6 TDI is equipped with an op-timised version of the two-stage chain drive used on all Audi diesel engines with a vee configuration. On the left cyl-inder bank the inlet camshaft and the high-pressure pump are driven by in-creased-diameter chain sprockets with a larger number of teeth (drive B, Figure 2).

In addition, the chain tensioner now op-erates on the outside instead of the in-side. This has led to a corresponding change in diameter in the basic drive (drive A, Figure 2) and increase in the curve radii at the guide rails of this drive. These measures, already applied in the same form to the 4.2l V8 TDI, have enabled the chain forces in both drives to be lowered by more than 30 %, and the equivalent friction values re-duced as well. The result is a drop of as much as 0.08 bar in the mean friction pressure of the timing gear components within the engine’s operating range. Furthermore, the reduced chain forces permit the new Bosch CP 4.2 increased-efficiency high-pressure pump to be in-stalled. Compared with the previous Bosch CP 1H pump, the higher torque needed by the pump calls for the timing gear to be significantly more rigid. The drive to the auxiliaries (drive D, Figure 2) has also been revised in design with the aim of reducing friction. Compared with the original device, the tensioning system has been transferred from the slack run of the chain to the tension side. This greatly reduces the length of the rails and results in a layout with higher curve radii. This chain is now of roller rather than sleeve pattern, which

The Authors

Figure 1: Full-load values for the V6 TDI 3.0 l in the Audi Q5

Dipl.-Ing. Richard Bauder is Head of diesel Engine development at Audi AG in Neckar-sulm.

Dipl.-Ing. Manfred Bach is Head of diesel Engine design at Audi AG in Neckar-sulm.

Dipl.-Ing. Markus Köhneis Head of V6 diesel Engine design at Audi AG in Neckar-sulm.

Dipl.-Ing. Danilo Rossiis Head of Mechanical development, V6 diesel Engines at Audi AG in Neckar-sulm.

Dr.-Ing. Henning Hoffmann is Head of Mechanical development, diesel Engines at Audi AG in Neckarsulm.

Dipl.-Ing. Christoph Strengis Team Coordinator, diesel Engine Thermo-dynamics at Audi AG in Neckarsulm.

Special Edition ATZ and MTZ i June 2008 37

yielded advantages in terms of reduced friction loss and more agreeable chain drive acoustics.

3 Oil Pump with Volumetric Flow Control and Two Pressure Stages

Another measure designed to reduce the engine power needed to overcome friction is the adoption of an oil pump with volumetric flow regulation and two pressure stages. The new V6 TDI is equipped with a vane-type pump with a rotating ring to adjust the discharge characteristic, Figure 3. The ring is ad-justed by oil pressure impinging on two control faces and overcoming the force exerted by a control spring, with the re-sult that the outgoing volume of oil is reduced. The first control face is ex-posed to the oil pressure present at the input to the main bearings; this ensures that the flow volume from the pump is adjusted to the volume of oil the engine actually needs. The second control face is supplied with the bearing input pres-sure by the switching action of a sole-noid valve. In conjunction with the first control face, two oil pressure levels with volumetric f low control can thus be generated. The lower pressure level cuts in according to engine load and speed, oil temperature and other operating pa-rameters. Altogether, thanks to the

adoption of volumetric flow control and the two pressure stages, the power need-ed to drive the pump can be as much as 50 % lower within the engine’s operat-ing range.

4 EGR Cooler of Modular Aluminium Construction

On modern diesel engines, cooled ex-haust gas recirculation (EGR) is a major factor contributing to compliance with exhaust emission limits. On Audi’s new V6 TDI, an innovative type of EGR mod-ule that combines the functions of EGR cooler, EGR valve and EGR bypass includ-ing actuation into a single unit is used, Figure 4. The module consists of two pres-sure-cast aluminium cooler elements that are slid into two housing sections also made from pressure-cast alumin-ium. The gastight joint between the com-ponents is produced by friction welding. The housing section on the valve side in-corporates a separate duct to cool the by-pass flap valve and EGR valve.

The electric EGR valve, the bypass valve and its actuating mechanism, the coolant thermostat and the cooler mount are integrated directly into the housing. Heat is exchanged between the exhaust gas and the coolant at the module’s in-ner cooling elements, around which the coolant flows. The ribs on the gas side of

Figure 2: Chain drives

Figure 3: Oil pump with volumetric flow control and two pressure stages

Audi Q5

Audi Q538

Aggregates | Diesel EnginesD

OI:

10.1

365/

s401

11-0

08-0

050-

5

the cooler elements were optimised by means of extensive flow simulations and matched to the density of the exhaust gas, which increases with the length of the cooler. Compared with the EGR sys-tem on the previous engine, introduc-tion of the new EGR module has in-creased cooling performance by 20 % and at the same time lowered pressure loss in the EGR system by 10 %. This ena-bles the levels of EGR needed to lower the content of oxides of nitrogen to be re-duced; this has a positive effect on the charge cycle and therefore on fuel con-sumption. Furthermore, the increased cooling performance permits greater freedom in the choice of engine manage-ment settings; this can be used to pro-vide an optimal be rating.

5 Summary

The measures stated here have resulted in a further significant reduction in the fuel consumption of the new V6 TDI en-gine for the Audi Q5 compared with the Euro 4 versions in current series produc-tion. At the optimal point on the con-sumption characteristic, a value of 198 g/kWh is obtained. The engine’s exhaust emissions are now below the Euro 5 lim-its, and the performance achieved by the Audi Q5 puts it ahead of its competitors, Table. The new V6 TDI 3.0 l is further im-pressive confirmation of the advantages of TDI technology: supreme torque and high power output over a broad usable engine-speed range are the key to an ex-ceptionally agreeable driving experience.

Excellent engine efficiency and low fuel consumption are combined with out-standing journey refinement.

References[1] Bauder, R. and H.-W. Pölzl: The history of the Tdi

engine at Audi. in: MTZ special issue ‘Ten years of Tdi engines at Audi’, 1999

[2] Bach, M., Bauder, R., Hoffmann, H., Krebser, R., Pölzl, H.-W. and S. Ribes-Navarro: The Audi V6 Tdi engine, Part 1: design and mechanical features. in: MTZ 64 (2003), No. 5

[3] Bauder, R., Bechle, S., dorsch, W., Pölzl, H.-W., Riegger, R., and H.-J. Schiffgens: The Audi V6 Tdi engine, Part 2: Thermodynamics. in: MTZ 64 (2003), No. 7-8

[4] Anton, C., Bach, M., Bauder, R., Franzke, G., Hatz, W., Hoffmann, H. and S. Ribes-Navarro: The new Audi V6 Tdi engine, Part 1: design and mechanical features. in: MTZ 65 (2004), No. 7-8

[5] Bauder, R., Brucker, d., Hatz, W., Lörch, H., Macher, A., Pamio, Z.-G., Reuss, T., Riegger, R. and H.-J. Schiffgens: The new Audi V6 Tdi engine, Part 2: Thermodynamics, application and exhaust post-treatment. in: MTZ 65 (2004), No. 9

[6] Bach, M., Bauder, R., Hoffmann, H., Riegger, R. and H.-J. Schiffgens: The new 3.0-litre V6 Tdi in the Audi A4: sporty and environmentally acceptable. in: ATZ-MTZ special issue ‘The new Audi A4’, 2007

Figure 4: EGR module

Table: Audi Q5 3.0 TDI performance

Special Edition ATZ and MTZ i June 2008 39