Crossover Audi SQ7: diesel 4.0 TDI and its electro mechanical supercharger

Not in Geneva, but in Ingolstadt – the “charged” SUV SQ7 TDI is presented at Audi headquarters the day after the official presentations at the Geneva Motor Show ended. Not that the sports Q7 did not fit on the exhibition stand, but the Ingolstadt people found an extra reason to draw attention to such a “clerical” event as the press conference following the publication of the annual report of the Audi Group and separately emphasize the company’s efforts to modernize diesel technologies.

In 2015, the company set another record sales – 1.8 million cars worldwide – which earned it 4.8 billion euros of operating profit. But we will leave millions and billions for later, because the SQ7 TDI is not only the first big crossover in the “eco” line, but also the world’s first production car with an engine equipped with an electro mechanical supercharger. The pioneer engine was the diesel V8 4.0 TDI (working volume 3956 cm 3 ), developed on the basis of the traditional 4.2 TDI turbodiesel, which is now only installed on Audi A8 sedans and develops 385 hp. and 850 Nm of torque.
But the amount of refinement is such that it turned out a completely new engine, which retained only the family architecture of the block of cylinders with the collapse of 90ยบ. Much more in common now with the petrol “eight” 4.0 TFSI (3993 cm 3 ), which is used on cars Audi and Bentley. In the diesel engine, the “hot” and “cold” sides of the block are reversed in the same way: the intake system is now located on the outer sides, and the outlet system is in the collapse of the block.
Two traditional turbochargers are still responsible for supplying air to the cylinders. They are connected in a series circuit: at low and medium speed, one supercharger operates, and the second one is connected only under high load. But between the intercooler and the intake manifolds there is another supercharger driven by a compact electric motor with a power of 7 kW (9.5 hp). The impeller of this compressor can be untwisted up to 70 thousand revolutions per minute and in order to get involved in the work, it needs only 250 milliseconds. The electric compressor starts immediately after starting the engine and is designed to compensate for the turbojammer effect.
In addition, the 4.0 TDI engine became the first diesel engine with a system for changing the stroke of the intake and exhaust valves. Each of the cams on the camshafts responsible for the intake has two profiles: for operation at low and high speed. The exhaust valves work in a different way. At low rpm, while only the electric blower and one turbocharger “blow”, only one outlet valve remains active for each cylinder. The second valves begin to work simultaneously with the second turbocharger – and direct their flow of exhaust gases only to its impeller.
As a result, for the maximum torque, the new diesel comes out with idle speed! All 900 Nm available in the range of 1000-3250 rpm, and the maximum power is 435 hp. This is less than the development of the 500-horsepower 6.0 V12 diesel on the previous-generation Q7 crossover, but more than the 381 hp that the most powerful BMW 3.0 diesel with the three turbochargers produces.

Audi SQ7 TDI with such a motor and an eight-speed “automatic” can accelerate to 100 km / h in 4.8 seconds, but the maximum speed is limited to 250 km / h. Passport consumption of fuel is 7.4 liters per 100 kilometers. To combat harmful substances in the exhaust, the new diesel uses the urea injection system in the exhaust manifold, the absence of which on mass diesel engines and became one of the reasons for the diesel scandal around the Volkswagen concern .
Interestingly, the electrocompressor required the use of an additional 48-volt electrical system (with its own 470 Watt-hour battery) on the crossover and a converter that allows a new, more powerful generator to charge this battery with a conventional 12-volt battery.
In addition, from the 48-volt system is fed and the system of active stabilizers of lateral stability – with built-in electro-actuators. Thus, Audi SQ7 TDI became the second after crossover Bentley Bentayga the car equipped with similar stabilizers with a 48-volt power supply system.
In addition, the “charged” Q7 differs from the basic active rear differential, reconfigured suspension and full-mounted chassis as standard.