INGOLSTADT, Germany -- Audi is giving electric superchargers their first production application with the SQ7 as it leads the race to increase diesel-engine power.
The SQ7, a sporty variant of the Q7 large SUV, will debut a V-8 4.0-liter diesel engine that adds an electric supercharger to two traditional turbos.
"The SQ7 is a strong confirmation of Audi's technology leadership and of our belief in diesels," CEO Rupert Stadler said on the sidelines of the automaker's financial results presentation on March 3.
Stadler said the SQ7 will be the world's most powerful automotive diesel engine, but will also offer reasonable fuel consumption figures.
With 435 hp of power and 900 Nm (663.8 lb ft) of torque between 1,000 and 3,250 rpm, the SQ7 diesel has a sportscar acceleration, sprinting from 0 to 100 kph (62 mph) in 4.8 seconds and on upwards to a 250 kph (155 mph) electronically limited top speed.
In the New European Driving Cycle (NEDC), the SQ7 uses 7.4 liters per 100 kilometers (31.8 U.S. mpg/38.1 UK mpg) which equates to carbon dioxide emissions of 194 grams per kilometer (312.2 g/mile).
The SQ7's V-8 diesel becomes VW Group's biggest automotive diesel engine after the company stopped production of its V-10 and V-12 units.
The engine easily outperforms its German rival's engines, which are 3.0-liter 6-cylinder units. BMW's 6-cylinder-in-line delivers 381 hp, while Mercedes-Benz's top diesel is a V-6 delivering 258 hp.
No turbo lag
The SQ7's supercharging system consists of three elements: two exhaust-gas powered traditional turbos, one small and one large, and an electric supercharger.
The main benefit of electric supercharging is almost zero turbo lag. Traditional turbos, activated by exhaust gases, need the engine to reach a certain rotation per minute level to begin increasing airflow pressure in the combustion chamber and thus to boost output. This delay in boost is called turbo lag.
In the SQ7 engine, the electric supercharger takes about a quarter of second to activate and quickly spins the small turbo to its effective 70,000 rpm level. The intervention of the electric supercharger lasts for 2 to 3 seconds, and then exhaust gases reach the necessary pressure to give the traditional turbo its required energy.
Over 2,500 rpm, the small traditional turbo is bypassed as the second, larger turbo comes in to play to boost output up to 435 hp.
The electric supercharger needs 48 volts to operate, which is provided by a subsystem added on to the traditional 12 Volt electric architecture of the vehicle.
The 48 Volt subsystem also has the advantage of making the active stabilizing bar control system react faster than those controlled by a traditional 12 Volt system, Audi said.
The SQ7 will go on sale in spring priced at 89,900 euros in Germany.
