Audi V-6 Remains Industry Benchmark

If you were an auto maker armed with a powerful, highly refined and fuel-efficient V-6 gasoline engine, what would you do with it? Make it your performance option in U.S. compact cars? The volume engine for midsize cars? The base engine for large luxury cars and cross/utility vehicles?

Why not all of the above?

Check, check and check.

That’s because we're not talking about just any V-6, but a DOHC, 24-valve, direct-fuel-injected, supercharged, all-aluminum engine capable of generating upwards of 350 hp. It's not inexpensive, but Audi does not sell inexpensive vehicles.

This powerful, smooth and oh-so-versatile powerplant earns Audi its fourth straight Ward's 10 Best Engines award for 2013 largely because it boasts "benchmark levels of torque, refinement and efficiency," WardsAuto judges assert.

As tested in a ’13 S5 quattro 3.0 TFSI coupe (where it replaced Audi’s superb but thirsty 4.2L V-8), it pumps out 333 hp at 5,500 rpm and 325 lb.-ft. (441 Nm) of torque from 2,900-4,500 rpm, good for sub-5-second 0-60 mph (97 km/h) runs.

WardsAutoeditors achieved between 19.6 and 21.2 mpg (12-11.2 L/100 km) city/highway compared with the S5's official rating of 17/26 mpg (11.2-9.0 L/100 km).

"Under light throttle," they report, "there is a strong launch followed by a creamy, luxurious trip through the gears. But hit the throttle hard, and there is a big gush of acceleration that takes the driver's breath away.... What makes this engine so special is the way it delivers torque, not how much it makes. It generates V-8-like thrust at very low rpm and then sends it to the wheels with a buttery smoothness that is utterly intoxicating."

Derived from Audi's retired 3.2L naturally aspirated V-6, this 3.0L TFSI is boosted by a belt-driven supercharger instead of an exhaust-driven turbocharger. That’s because engineers wanted instantaneous response and – unlike an intercooled turbo system – a forced-induction system compact enough to fit into the 90-degree V of the cylinder banks with sufficient hood clearance to meet European pedestrian-impact requirements.

Engineers considered both turbocharging and supercharging this engine before deciding on the latter. "Extensive comparative tests revealed the mechanical supercharger to be superior to a biturbo" for this application, they concluded.

Because this now is Audi's only V-6, one key priority was to ensure its suitability for use in a wide variety of vehicles. Besides the higher-performance S4 versions of Audi's A4 sedan and Cabriolet, it also powers the S5 coupe, A6 sedan, A7 4-door "coupe," Q5 and Q7 CUVs and top-of-the-line A8 luxury sedan. It's also offered in parent company VW's Touareg and Porsche's Cayenne CUV and Panamera Hybrid sedan.

"It's very versatile and tunable to suit whatever vehicle it's in," says Mark Fruechtnicht, Audi of America's product manager. "It starts at 272 hp in the Q7 and goes all the way up to 354 hp in the SQ5." He says about 20% of U.S. A6 sedan sales are 3.0L TFSI V-6-powered S6s. In the A6 family, where Audi also offers turbocharged 4-cyl. and (in the S6) V-8 engines, about 48% are V-6s.

"The A7 only comes with the V-6, and we've introduced it very successfully in our flagship A8, where the 3.0L TFSI vs. the 4.2L naturally aspirated V-8 is less of a trade-off than you would expect. We get similar performance and equal or better fuel economy, and the V-6 mix in the A8 today is 54% of the gasoline engines," Fruechtnicht says. In addition to the 4.2L V-8, versions of the A8 luxury sedan also are available with a gas V-12 or a TDI diesel.

The 3.0L TFSI V-6 is about 25% of the gas engines sold in Q5 CUVs and about 70% in Q7s. "It's a pretty hefty mix in all of these car lines," Fruechtnicht adds. "So it's a very important engine for Audi."

Audi spokesman Mark Dahncke says the 3.0L TFSI V-6 specifically is engineered and tuned for each application. "It can represent a performance engine in an S4, S5 or SQ5, or a very nice, refined entry engine in an A8 or a Q model, where the TDI is also part of the mix."

Another element of its mission is to work equally well with 6-speed manual and 8-speed automatic transmissions and with quattro all-wheel drive. It handles towing duties in the Q7 CUV while meeting both U.S. ULEV2 and European EU5 emissions standards.

The supercharger is an Eaton Roots-type unit with two water-to-air intercoolers integrated into its housing and two 4-vane rotary pistons that counter-rotate at up to 23,000 rpm to deliver as much as 2,205 lbs. (1,000 kg) of air per hour to the combustion chambers at pressures up to 11.6 psi (0.8 bar). The direct-injection system uses 6-hole injectors capable of three injections per combustion event at pressures of up to 2,175 psi (150 bar).

Efficiency-enhancing features include a pressure- and volumetric flow-controlled oil pump, a reduced-friction chain drive and lower piston-ring pretension friction.

Great as it is, this engine is four years old and likely will get an upgrade soon.

"The only thing we can say for certain is that (engineers) will look to increase both performance and efficiency and, if at all possible, reduce weight," Dahncke says.

But further down the road, as mandated corporate average fuel economy rules ramp up 4% to 5% per year between now and 2025, might Audi have to sacrifice some performance to achieve the required efficiency?

"We have not had to so far," Dahncke says, "So we will stick with that until someone tells us differently. We moved away from a standard 6-cyl. in our A4 and were first to offer a turbocharged 4-cyl. in that class. We were also first to introduce a turbo 4-cyl. in the midsize luxury sedan segment, and we brought the 3.0L TFSI into the A8 when only V-8s were available in the BMW 7-Series, the Mercedes S-Class and Lexus LS.

"We have demonstrated that we can downsize engines while improving both efficiency and performance. I don't know why that would change in the next five years. And in 10 years, we may be looking at a completely different engine lineup. I do think that it is feasible to continue on the path of improving both at the same time.”