Audi eliminates turbo lag in SQ7 turbodiesel

Electric compressor provdes near instantaneous low-end boost

Published: March 3, 2016, 1:20 PM
Updated: November 23, 2021, 2:51 PM

Audi SQ7

Audi is hoping to consign turbo lag to history with the introduction of the world’s first series production electrically controlled compressor for its 4.0-litre 8-cylinder turbodiesel in the Q7 sport utility coming at the end of summer 2016.

Housed in the Audi SQ7 TDI (the first S version of the Q7 and just the second S model SUV), the biturbo V-8 makes 429 hp and 664 lb‑ft of torque, making it the most powerful diesel on sale and enabling the SUV to accelerate to 100 km/h in 4.8 seconds. Combined fuel economy is rated at 7.4 L/100 km on the European cycle, and top speed is governed to 250 km/h.

“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,” said Dr. Stefan Knirsch, Member of the Board of Management of AUDI AG for Technical Development. “So equipped, the SQ7 TDI with a V8 TDI engine achieves the consumption figures of a 6-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.”

But the beauty of the system is not what it does but how quickly it does it, with reportedly immediate response. Working in sequence from exhaust gases, one turbocharger naturally provides boost under low and intermediate loads, while the second has to wait until higher loads to provide boost. The electric compressor helps the turbochargers by adding boost at lower engine rpm. It sits after the intercooler to push cool air into the first turbocharger and provide boost in less than 250 milliseconds, without the turbocharger having to wait for exhaust gases to start spooling it up. The electric compressor is powered by its own 48-volt lithium-ion battery.

Audi’s valvelift system also makes its debut in a diesel engine, delaying the opening of a second exhaust valve in each cylinder head until load and engine speed increases in order to deliver power more uniformly over the engine’s rpm range.

And in order to allow that, Audi also needs electromechanical active roll stabilization to keep the 7-seat vehicle’s body roll under control. Using compact electric motors that intertwine with each other at higher speeds, the suspension keeps body lean down in high-speed bends, helping to reduce front wheel push (which is further aided by optional 4-wheel steering). And because it requires no oil, the system is maintenance free. The front and rear stabilizers can also be adjusted independently of each other.

To set it apart from its stablemates, the SQ7 features a unique grille, side air inlets and aluminum capped mirror housings and door inlays. LED lights are standard, as are 20-inch alloy wheels. The interior features Audi’s virtual cockpit, centred on a 12.3-inch display, with multifunction touch controls, on-board WiFi and redundant controls on the steering wheel.

The standard sound system can be upgraded to a Bose Surround Sound system with 19 speakers, or to a Bang & Olufsen advanced system with 11 channels and 23 speakers.