Audi has become the first automaker to introduce a series-produced engine equipped with an electric turbocharger. The technology is making its global debut under the hood of the SQ7 TDI, a hot-rodded version of the second-generation Q7.
The SQ7 is equipped with a new, 4.0-liter TDI V8 mill that sends 435 horsepower and a stout 663 pound-feet of torque to all four wheels via an eight-speed automatic transmission. The electric turbo (called electric-powered compressor, or EPC, in Audi-speak) spools up at low engine speeds to virtually eliminate turbo lag by providing boost right off the line. A pair of conventional, exhaust-driven turbochargers mounted between the cylinder banks kick in sequentially at higher engine speeds to unlock the eight-cylinder’s full output.
The setup allows the SQ7 to hit 62 mph from a stop in 4.8 seconds — faster than an Alpha fighter jet, if Audi’s promotional video is to be believed — and reach a top speed that’s electronically limited to 155 mph. In spite of its impressive performance credentials, the SUV returns nearly 32 mpg in a mixed European cycle.
Power for the EPC comes from a 48-volt lithium-ion battery that’s located under the trunk floor and connected to the SQ7’s standard 12-volt electrical system by a DC/DC converter. Using a 48-volt sub-system allowed engineers to ensure the EPC always has the seven kilowatts of juice it needs to spool up, and it helps reduce the load placed on the regular 12-volt lead battery that powers the SUV’s other accessories.
The 48-volt system also feeds an electro-mechanical active body roll stabilization system that’s similar to the one that equips the Bentley Bentayga. Consisting of an electric motor and a three-stage planetary gearbox, the system improves handling by reducing body roll and understeer, and it maximizes comfort on rough roads by keeping bumps and vibrations out of the cabin. Audi promises it’s maintenance-free because, unlike the hydraulic setup it replaces, it doesn’t require any oil.