|Audi SQ7 TDI|
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With 320 kW (435 hp) and 900 Nm (663.8 lb ft) of torque, the new Audi SQ7 TDI is the most powerful diesel SUV on the market. It also leads the competition in numerous other technical fields. Its redesigned 4.0 TDI engine features a world first: An electric powered compressor gives the SQ7 TDI outstanding off-the-line performance. Yet it consumes on average 7.4 liters of fuel per 100 kilometers (31.8 US mpg).
"Following the launch of the successful SQ5, we are now also applying the concept of a diesel-engined S model to the Q7 model line. So equipped, the SQ7 TDI with a V8 TDI engine achieves the consumption figures of a six-cylinder. The new technology solution of the electric powered compressor in the SQ7 TDI is a world first in the competitive environment, with which Audi once again underscores its claim Vorsprung durch Technik," said Dr. Stefan Knirsch, Member of the Board of Management of AUDI AG for Technical Development.
The 4.0 TDI has been newly developed from the ground up. It combines best-in-class performance with low consumption and guarantees maximum dynamics. The V8 engine has a displacement of 3,956 cc. The two exhaust-gas turbochargers are activated selectively according to the concept of sequential charging, since exhaust gas only flows through one turbocharger at low and intermediate load. The second turbine is only activated at higher loads. An electric powered compressor (EPC) augments the work of the two turbochargers, particularly in the lower engine speed range, providing for extremely dynamic off-the-line performance.
With 320 kW (435 hp) and 900 Nm (663.8 lb-ft) of torque between 1,000 and 3,250 revolutions per minute, the SUV sets new benchmarks in the segment. It accelerates from 0 to 100 km/h (62.1 mph) in 4.8 seconds; top speed is 250 km/h (155.3 mph) (governed). In the New European Driving Cycle (NEDC), it consumes 7.4 liters per 100 kilometers (31.8 US mpg). This corresponds to CO2 emissions of 194 grams per kilometer (312.2 g/mi).
The electric powered compressor is a world first in a production vehicle. This EPC strongly supports the 4.0 TDI engine when starting off and accelerating from low load for pure dynamics with no turbo lag. It is placed in the air path downstream of the intercooler, close to the engine. Because the EPC does not require any exhaust-gas energy to develop boost, it can be used at any time, thus making it the solution for the traditional weaknesses of the classic exhaust-gas turbocharger. With this technology, turbo lag is history. The EPC provides the engine the boost energy needed for the dynamic delivery of power in less than 250 milliseconds. Driven by a compact electric motor, its compressor wheel spins up to 70,000 revolutions per minute. The 4.0 TDI thus develops its immense power with no perceptible lag: It is available immediately upon depressing the accelerator. That is a major plus, particularly when starting off.
The Audi valvelift system (AVS) is also making its debut in a diesel model from Audi. The inlet and exhaust cam shafts each have two cam contours per valve. On the inlet side, one cam contour supports starting off in conjunction with the EPC, while the other optimizes cylinder filling and thus power at high engine speeds. The AVS system on the exhaust side enables activation of the second exhaust-gas turbocharger. The sequential charging system controls the two exhaust-gas turbochargers so that only one turbocharger is used at low engine speeds. The second is activated additionally at higher loads and engine speeds. The customer benefits from very good torque delivery and dynamic response across the entire engine speed range.
The exhaust streams from the two exhaust valves are hermetically separated, with each driving one of the two turbochargers. In the lower engine speed range, one valve per cylinder remains closed, so that the full exhaust stream flows to the active turbocharger. When load and engine speed increase, the AVS opens the second exhaust valves. This directs flow to and activates the second exhaust-gas turbocharger. The engine achieves its maximum output in this biturbo mode. The switching by the AVS enables fast and precise activation of the second exhaust-gas turbine.
The power for the EPC, which reaches a maximum of 7 kW, is provided by the 48-volt electrical subsystem. The SQ7 TDI uses this higher-power electrical system, which facilitates the high-power systems electromechanical active roll stabilization (EAWS) and EPC. To meet their high power and energy requirements, the electrical subsystem includes its own 48-volt lithium-ion battery mounted beneath the luggage compartment with a nominal energy content of 470 watt-hours and peak output of up to 13 kilowatts. A DC/DC converter connects the 48-volt and 12-volt electrical systems. The required energy is provided by a more powerful and highly efficient generator with an efficiency of over 80 percent at an output of up to 3 kW. This is a so-called MOSFET generator (Metal Oxide Semiconductor Field Effect Transistor), which reduces electric losses and increases efficiency. MOFSETs replace the diodes used previously. In addition, the 48-volt storage unit supports the 12-volt electrical system when required. This also reduces the load on the 12-volt lead battery.
The intake side of the 4.0 TDI is on the outside, the exhaust side with the two turbochargers is on the inside of the 90-degree internal V. This layout provides for short gas paths, i.e. spontaneous response and short paths for the emissions control system. The common-rail system generates up to 2,500 bars of injection pressure. Ignition pressure reaches the 200-bar mark in broad sections of the characteristic.
The innovative thermal management and sophisticated measures in the crankshaft and camshaft drive reduce friction. With the combination of a NOx oxidating catalytic converter and a downstream SCR catalytic converter, which is integrated into the diesel particulate filter and uses AdBlue injection to reduce oxides of nitrogen, the V8 TDI has a particularly efficient emissions control system. A sound actuator in the exhaust system amplifies the sonorous eight-cylinder sound. SQ7 TDI drivers can choose how much attention they want to draw to themselves by using the Audi drive select system to vary the amount of sound.
The biturbo V8 combined with the EPC is a core element of the global Audi diesel strategy. With high torque even at low engine speeds and low consumption figures, it is also ideally suited for markets such as the United States. Its engine characteristic combines supreme pulling power with sporty agility - ample off-the-line performance and spontaneous response.
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|Article||Image gallery (18)||Specifications|