Audi SQ7: World's most powerful diesel SUV

Electric turbochargers have been around the aftermarket for years and the Volkswagen Group announced back in 2013 – a year after we drove an Audi A6 Electric Biturbo V6 prototype – that it was developing diesel engines equipped with e-turbo technology.

Now, the advanced turbo technology is a reality, with Audi – in a classic 'top-down' release strategy – revealing its first SQ7, based on the second-generation Q7 large SUV, powered by a new 4.0-litre V8 diesel with the world's first production electric 'turbocharger'.

Strictly speaking, it's not a turbo since it is not exhaust-driven, and nor is it a supercharger in the original sense of the word, because it's not mechanically driven – hence Audi's use of the German term, compressor.

However, the electric compressor is used to spin up a pair of conventional mechanical turbochargers instantly, forcing air into the cylinders before the exhaust gases arrive at higher revs. Once those exhaust gases are on station to do their normal work, the electric 'turbo' is bypassed and the mechanical units take over.

Audi puts it thus: "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."

The SQ7 TDI's e-compressor system relies on a 48-volt electrical subsystem and performance outputs are 320kW of power and a beefy 900Nm of torque between just 1000 and 3250rpm, which is less than the old 368kW/1000Nm Q7 6.0 V12 TDI but enough for Audi to claim it's the world's most powerful diesel SUV.

The new SQ7 will join Audi Australia's Q7 line-up in the third quarter of this year, followed by a cheaper new entry-level 160kW version of the V6 diesel-powered Q7 3.0 TDI later this month, before the plug-in Q7 TDI e-tron goes on sale here late this year.

Expect a price tag of about $180,000 -- significantly more than the sole Q7 3.0 TDI now on sale for $103,900 (the 160kW version will undercut $100,000), positioning it at the top of the new Q7 line-up, but well below the circa-$250,000 price of the previous-generation Q7 6.0 V12.

Audi says its most powerful Q7, which was spied testing at the Nurburgring last June, delivers outstanding standing-start acceleration and a stunning 0-100km/h time (for a two-tonne-plus vehicle) of just 4.8 seconds. Top speed is limited to 250km/h.

Despite the epic performance, the SQ7 consumes diesel at the rate of just 7.4L/100km on Europe's NEDC test cycle, which equates to 312g/km of CO2 emissions.

Audi says the SUV's output, flexibility and fuel consumption sets a new benchmark in its segment, and that the latter matches the efficiency of a six-cylinder diesel, such as the one that powers Audi's first S-badged SUV, the SQ5.

Audi's new V8 super-diesel, which is effectively a downsized, high-tech 3956cc version of the 4.2-litre TDI bent eight in the old Q7 and Porsche's Cayenne (as indicated by former Audi technical director Dr Ulrich Hackenberg last April also sees the SQ7 eclipse BMW's triple-turbo BMW X5 550d.

The 7kW EPC, which spins at up to 70,000rpm and provides boost in less than 250 milliseconds, eliminating traditional turbo lag, isn't the SQ7's only new technology. The 90-degree V8 runs a common-rail injection system with up to 2500-bar of pressure.

Also debuting here is the Audi valvelift system (AVS), in which the inlet and exhaust camshafts each have two cam contours per valve. On the inlet side, one cam contour aids the EPC in low-speed engine performance, while the other optimises cylinder charging and thus power at high engine speeds.

Making it a sequential charging system, the AVS system on the exhaust side activates the second turbocharger. The exhaust streams from the two exhaust valves are hermetically separated, with each driving one of the two turbochargers.

At lower engine speeds, one valve per cylinder remains closed so the full exhaust stream flows to the active turbocharger. When load and engine speed increase, the AVS opens the secondary exhaust valves, directing flow to the second turbocharger and providing maximum boost in biturbo mode.

Like the standard Q7, the SQ7 comes with electromechanical power steering, the Audi drive select driving dynamics system and adaptive air suspension with S-specific tuning as standard.

As seen in the spy pics, an optional carbon-fibre ceramic brake disc package will be available, while 22-inch alloy wheels will also be on offer alongside the standard 20-inch alloys with 285/45 tyres.

New for the SQ7 chassis is a quattro sport differential with rear-axle torque vectoring, making the 5.07-metre SUV the sportiest in its segment, says Audi.

Exterior cosmetic extras include a unique grille, bumpers, side air inlets, mirror housings, door inlays, four rectangular 'twilight' exhaust outlets and LED headlights (Matrix LED headlights will be available).

In Europe, the SQ7 will be offered in both five- and seven-seat forms, and with a range of interior Valcona leather colours, including Kodiak brown with contrasting stitching, plus Alcantara black headlining and sport seats with contrasting stitching, luxury velour floor mats and the option of Sono aluminium and carbon twill copper trim strips.

A 1920-Watt, 19-speaker Bose sound system is standard, but two removable front seatback-mounted Audi tablets are further multimedia options.

Of course, all of the Q7's safety systems are here too, including Audi pre sense city AEB and adaptive cruise control.