Audi premieres high-efficiency turbo four-cylinder

At the Vienna Motor Symposium today, Audi unveiled a new, high-efficiency turbocharged four-cylinder TFSI engine that will go into production by the end of this year and power the newest A4 sedan.

At first glance, the 2.0L motor looks a lot like the one used across the Audi (and Volkswagen) line now, but trades some power for a focus on efficiency: the new engine is rated at 190 hp and 236 lb-ft of torque, down from 220/258 in the brand’s current two-point-oh turbo.

The big change is in how the engine burns fuel fed to it by the familiar direct injection system, using a modified version of the Miller combustion cycle. Instead of keeping the intake valve open after the piston has reached the bottom of its stroke, Audi engineers instead shortened the intake time, using the turbocharger to ensure what the company calls “optimal cylinder charges.”

In addition to the direct fuel injection used in current TFSI motors, Audi’s new 2.0L also includes upstream fuel injection (like the dual-injection system in Lexus’ 3.5L V6) that works at partial engine load to provide a more efficient air/fuel mixture, and variable valve timing changes intake duration depending on full versus partial loads.

Until the engine is bolted into a production car and run through fuel economy tests, we won’t what kind of efficiency benefits the new tech will allow, but Audi says to expect sub 5.0 L/100 km results in highway driving.