Supercharged, Turbocharged? Volvo's New Engine Is Both

It's already that time of year when the Swedes flee to the French Riviera to escape the rains. So we take the wheel of the 2015 Volvo S60 T6 in Saint-Paul-de-Vence, a medieval town that looks like it was painted into the foothills of the Maritime Alps. Predictably, its streets are barely wide enough for a couple peasant carts, and we hurry off to the local mountain roads.

Like other Volvo S60s we've driven, this one is enjoyable to drive briskly on roads with tight turns. We floor the throttle to get around a delivery van, and the thrust is there all right, but it feels quite different from the 2011 Volvo S60 T6 we tested. The supercharger whine will stick with us for days, and the torque curve is as flat as the dark blue Mediterranean hundreds of feet below.

New Engine Is Supercharged and Turbocharged

Instead of Volvo's familiar turbocharged inline six-cylinder engine, our preproduction 2015 Volvo S60 T6 test car has a new 2.0-liter inline four-cylinder that uses both an Eaton supercharger and a Borg-Warner turbocharger with an air-to-air intercooler. Rated at 302 horsepower, it's the most potent gasoline engine in Volvo's new Drive-E family of direct-injected 2.0-liter engines that will eventually include four gas motors and four diesels.

Supercharger noises will be more subdued on production cars, we're told, but that big, useful band of torque is a defining feature of this new-generation T6 engine.

"Most customers don't drive at the extremes of [their car's] engine; they drive down at about 30 percent of the capacity of the engine," Derek Crabb, Volvo's vice president of powertrain engineering, says, "and when they say the engine is powerful, [they're talking about] responsiveness, because the engine picks up and goes away very quickly.

"On the high-performance gas engine, we put a supercharger as well as a turbocharger, because the supercharger is directly connected to the engine and that gives you that immediacy of response."

Although the four-cylinder makes less grunt than the old turbo inline-6 (295 pound-feet versus 325 lb-ft), it comes on at just 2,100 rpm and sticks around until 4,500 rpm (instead of 4,200) and doesn't drop off much until 5,000. The supercharger is active until 3,500 rpm, but by then the turbo has a full head of steam that carries you through to 6,000 rpm before power levels off.

New Eight-Speed Automatic, Plus Electric Steering

An all-new Aisin-Warner-sourced eight-speed automatic transmission helps make the most of the smaller engine's power thanks to a wider range of ratios than the six-speed automatic in Volvo's current lineup. As we cruise Cote d'Azur's main highway, La Provençale, at its 110-km/h (68-mph) posted limit in morning traffic, the engine loafs at 1,800 rpm.

Left in Drive, the new automatic shifts quickly enough to suit our brisk but comfortable pace. A sport mode provides quicker shifts, though, and steering-wheel-mounted paddle shifters make it easy to change gears manually when the mood strikes (though we don't detect an obvious attempt to rev-match downshifts).

Volvo officials tell us that this drivetrain is strong enough to get our front-wheel-drive 2015 Volvo S60 T6 to 60 mph in 5.6 seconds. If true, that's quicker than the last six-cylinder S60 T6 we tested (5.9 seconds).

Along with the new engine, our 2015 Volvo S60 T6 test car features a new electric-assist power steering system. It's quite likable, with good stability on-center and excellent precision through all those turns. The use of EPS has also allowed Volvo to offer an active lane-keeping feature, and like other systems of its kind, it gently applies torque to the wheel to nudge you back into line.

Four Cylinders for All, Eventually

In late January 2014, the new-generation T6 engine and eight-speed automatic will arrive in the U.S. under the hoods of the S60 sedan and XC60.

The second-from-the-top gas engine, known as the T5, even though it, too, is a four-cylinder, will find a home in the new V60 and base versions of the S60, XC60, XC70 and S80. When equipped with this engine, they'll also use the eight-speed automatic.

We don't get to sample the new T5, which has a single turbocharger, but it's rated at 241 hp and 258 lb-ft of torque, a little shy of the numbers on the turbo inline-5 that goes by the same name. However, Volvo claims the V60 T5 will earn a 29 mpg EPA combined rating, which would be a vast gain in efficiency over the five-cylinder. Our similarly sized long-term 2012 S60 T5 averaged 23 mpg.

Note that the new T5 and T6 four-cylinder engines will only be offered on front-drive models for the 2015 model year. All-wheel-drive models will continue to use the company's five- and six-cylinder engines for a couple more years.

Why Go To So Much Trouble?

Developing a new batch of four-cylinder engines that will be used by nearly every Volvo model was no small undertaking. But company officials say they had to do it to satisfy looming fuel-efficiency rules.

"In Europe, we've got to reach an average of 95g of CO2 per km by 2020, which everyone thinks about," Crabb says, "but by 2025, it's got to be 75g/km, which is just immensely challenging, which means we're going to [need] electrification plus the best possible fuel economy from the internal combustion engine."

Volvo officials also insist the new engines, combined with the new platform architecture that will debut on the redesigned 2015 Volvo XC90, will ultimately make their cars less expensive to build.

"There's a lot of commonality [among the engines] so you could put them on the same line," says Peter Mertens, Volvo's senior vice president of research and development. "It helps us in manufacturing efficiency, but it also helps us in packaging the front end only once. So for the 60, 70, 80, 90, all the S, V and XC cars, we will have exactly the same front end. That's a dream from a manufacturing point of view."

A Family of Turbos and Plug-In Hybrids

Every engine in the new Drive-E family has an 82mm cylinder-bore diameter and a 93.2mm stroke. The bedplate, crankshaft, connecting rods and oil pump are shared between gas and diesel. The cylinder heads are different, of course, and the diesels have a taller deck height (to accommodate higher-compression pistons) and stronger cylinder liners (so the aluminum block can withstand a pounding).

All of the engines use forced induction. Most make do with a single turbocharger, while the top two diesels get twin turbos. We take a quick drive in a European-spec V60 equipped with the second-from-the-top diesel engine (known as the D4) and the eight-speed automatic. This engine only makes 178 hp, but its 295 lb-ft of torque hits at just 1,750 rpm. It has more low-end kick than the new T6 gas engine and, honestly, we think it sounds better, too. But we won't see diesel Volvos in the U.S. anytime soon.

"It is already difficult to make money with gas engines in the U.S. by having that strong Swedish krona," Mertens tells us. "With diesels being even more expensive, it's close to impossible right now for us. It sounds like a bit of a cheap excuse, but it's the reality."

Instead, Volvo will offer plug-in hybrids to satisfy Americans' desire for torque.

"If someone really wants to have V8 power," Mertens says, "we'll put an electric motor on the rear axle and a battery in the tunnel, and then you have more than 400 hp and more than 600 Nm [443 lb-ft] of torque. With that, you have V8 performance even though you have only a four-cylinder engine in the front."

A Better Engine for Better Times?

Although the new T6 engine in the 2015 Volvo S60 isn't overflowing with personality, it's powerful enough to accelerate past French motorists while the new eight-speed automatic serves up smooth gearchanges. Combine that with the higher mpg ratings the company is predicting, and the four-cylinder T6 models probably won't feel like a step down from the six-cylinders. Volvo expects 60 percent of U.S.-spec S60s will be sold with the new engine during the 2014 calendar year.

Mind you, we'd still rather have one of the new diesels in the 2015 S60. But Volvo's U.S. lineup has been starved of new product over the last couple years, and while the new gasoline four-cylinders aren't a cure-all for this neglect, they're a step in the right direction.

Year Make Model: 2015 Volvo S60 T6 4dr Sedan FWD (2.0L 4cyl 8A) Vehicle type: FWD 5-passenger 4dr Sedan Estimated MSRP: TBD Assembly location: Torslanda, Sweden Configuration: Transverse, front engine, front-wheel drive Engine type: Supercharged and turbocharged, direct-injected inline-4, gasoline Displacement (cc/cu-in): 1,969/120 Block/head material: Aluminum/aluminum Valvetrain: DOHC, 4 valves per cylinder, variable intake- and exhaust-valve timing Compression ratio (x:1): 10.3 Horsepower (hp @ rpm): 302 @ 5,700 Torque (lb-ft @ rpm): 295 @ 2,100-4,500 Transmission type: Eight-speed automatic with Sport/Manual modes Transmission ratios (x:1): I = 5.25, II = 3.03, III = 1.95, IV = 1.46, V = 1.22, VI = 1.00, VII = 0.81, VIII = 0.67, R = 4.01 Final-drive ratio (x:1): 2.77 Suspension, front: Independent MacPherson struts, coil springs, twin-tube dampers, stabilizer bar Suspension, rear: Independent multilink, coil springs, twin-tube dampers, stabilizer bar Steering type: Electric-assist, speed-proportional rack-and-pinion steering Tire make and model: Bridgestone Potenza S001 Tire type: Summer performance Tire size: 19-by-8 inches front and rear Wheel material: Cast aluminum alloy Brakes, front: 12.4-inch ventilated disc Brakes, rear: 11.9-inch ventilated disc 0-60 mph, mfr. claim (sec.): 5.6 Fuel economy, mfr. est. (mpg): TBD Fuel tank capacity (U.S. gal.): 17.8 Stereo description: AM/FM/CD stereo with HD radio and eight speakers (optional 12-speaker Dolby ProLogic II system) iPod/digital media compatibility: Standard USB and auxiliary inputs; Bluetooth audio connectivity Satellite radio: Standard Bluetooth phone connectivity: Standard Navigation system: Optional Parking aids: Available rearview camera (depending on trim level) Blind-spot detection: Optional Adaptive cruise control: Optional Lane-departure monitoring: Optional Collision warning/avoidance: Optional Length (in.): 182.5 Width (in.): 73.4 Height (in.): 58.4 Wheelbase (in.): 109.3 Track, front (in.): 62.1 Track, rear (in.): 62.0 Turning circle (ft.): 37.0 Legroom, front (in.): 41.9 Legroom, rear (in.): 33.5 Headroom, front (in.): 38.3 (37.4 with sunroof) Headroom, rear (in.): 37.4 Shoulder room, front (in.): 57.0 Shoulder room, rear (in.): 55.2 Seating capacity: 5 Trunk volume (cu-ft): 12.0 Bumper-to-bumper: 4 years/50,000 miles Powertrain: 4 years/50,000 miles Corrosion: 12 years/Unlimited mileage Roadside assistance: 4 years/Unlimited mileage (renewable) Scheduled Maintenance: Complimentary at 10,000-, 20,000- and 30,000-mile intervals

Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.