2012 Audi A5 CoupeEnlarge Photo
Audi isn't the first name in high-mpg luxury cars--it has yet to release a hybrid, though it has several on deck, including the A6 Hybrid, which we won't get here in the U.S. But Audi does have its diesel engines, and those manage pretty solid economy while maintaining a level of performance thanks to the high torque figures. But soon, a new engine may add to Audi's green porftolio--and it's neither diesel nor hybrid.
Instead, it's a highly efficient turbocharged four-cylinder gasoline engine: the completely redesigned 1.8 TFSI. As the base engine--for Europe, at least, though there's some indication it will come to the U.S. as well--it isn't expected to be particularly sporting, but it delivers 170 horsepower and 236 pound-feet of torque while turning out 41.27 mpg U.S.
Those are diesel-like figures, all around--high torque, high efficiency, and a bit more horsepower than the average 2.0-liter turbodiesel, including the VW Group's own 2.0 TDI. So how does the 1.8 gasoline-burner do it? Through lots of technology.
The turbo, for instance, uses boost pressures up to 1.3 bar (19 psi) thanks to a new alloy that can withstand higher temperatures, An oxygen sensor mounted upstream of the turbine wheel, a compressor wheel machined from a solid blank, and an electric wastegate actuator all help to make the turbo more efficient by allowing the system to adjust boost pressure quickly with an eye toward maintaining power while reducing fuel consumption.
Higher pressure in the direct injection system, along with two or three injection stages per cycle, help ensure fuel is delivered more efficiently and optimally. To make sure the fuel burns more efficiently, the new 1.8 TFSI adds indirect injection, too: shooting fuel into the end of the intake manifold just before the tumble valves, better incorporating the fuel into the swirling air. A two-stage valve lift control system helps maximize power and efficiency through two camshafts on the exhaust side.
Beyond the fuel, intake, and timing manipulations, the new 1.8 TFSI also uses a completely electronic coolant regulation system, skipping the traditional thermostat for an electric motor-driven module that controls the flow of coolant. It's used to keep the coolant in the crankcase longer than normal at startup to warm the oil sooner, bringing the engine to ideal operating temperature more quickly. It's a small savings: Audi says the electronic coolant system scavenges 4.02 grams of CO2 per mile.
There's even more to this engine, so if you're still hungry for details, hit page two for the full release.
As you may have noticed, the new 1.8 TFSI is just a bit behind the current standard engine option in the U.S. A5, the 2.0T. At 211 horsepower and 258 pound-feet of torque, it's definitely a bit sharper than the 1.8 TFSI--but even so, we think it's possible some would settle for a little less power and not too much less torque for 10-15 mpg improvement in fuel economy. Would you?
New 1.8 TFSI turbocharged four-cylinder for the Audi A5Enlarge Photo