Audi’s new SQ7 TDI comes with 429 horsepower and 663 lb-ft thanks to an electric compressor, two turbochargers and a trick 48‑volt electrical subsystem. They say this wonderdiesel is also “ideally suited for markets such as the United States.” The way things are going, we’ll see about that, but the SQ7 is still very impressive.
Audi claims this is the world’s first series production car combining turbocharging with an electrically powered compressor, but we beg to differ.
Either way, the Germans use a different method to end turbo lag as we know it, involving an electric compressor placed in the air path downstream of the intercooler, and an extra 48‑volt lithium-ion battery mounted beneath the luggage compartment.
The 4.0-liter TDI uses two exhaust-gas turbochargers which are activated selectively. Exhaust gas only flows through one at low and intermediate load, with the second turbine joining the party at full throttle. The electric compressor (EPC) helps those turbos across the whole speed range. It can be used at any time, activating in less than 250 milliseconds and spinning at up to 70,000 revolutions per minute.
The new diesel also got Audi’s valvelift system for the first time, with the inlet and exhaust cam shafts each having two cam contours per valve. On the inlet side, one cam contour supports starting off in conjunction with the compressor, while the other optimizes cylinder filling and thus power at high engine speeds. On the exhaust side, the valvelift activates the second turbo as well by opening the second exhaust valves.
The electric compressors power output reaches a maximum of 7 kW, which is provided by the 48‑volt electrical subsystem. The SQ7 TDI uses this to power the electromechanical active roll stabilization as well.
There’s a separate 470 watt-hour lithium-ion battery beneath the boot floor, with a DC/DC converter connecting the 48‑volt and 12‑volt electrical systems. The required energy is provided by a MOSFET generator with an efficiency of over 80 percent at an output of up to 3 kW. This also reduces the load on the 12-volt lead battery.
Audi says the V8 TDI is clean too. Efficiency is guaranteed by the common-rail system working at 36,259 psi, reduced friction and 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.
All this pulling power is going to the wheels through an eight-speed tiptronic, making the SQ7 accelerate to sixty in 4.8 seconds.
The aforementioned electromechanical active body roll stabilization system uses a compact electric motor with a three-stage planetary gearbox separating the two halves of the stabilizer. On an uneven road surface, they are actively decoupled from one another, resulting in improved ride comfort. During faster driving, the tubes are interconnected and twisted against each other.
This significantly reduces body roll, improving steering precision and the agility. Audi says that compared to a conventional hydraulically switched unit, the 48 volt-based system can develop more power, it works faster and it is activated even at low speeds. And because it requires no oil, it is also maintenance-free and kind to polar bears.
You can also opt for four-wheel steering, a torque-vectoring sport differential, up to 22 inch wheels and a choice of two sound systems. The Bose Surround comes with 19 speakers, while Bang & Olufsen’s has a total of 23.
Because disco is back.
Will that do, America? It sure as hell will for Europe...
Photo credit: Audi
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