Volvo Cars unveils at this week's Geneva auto show its '07 S80 flagship and an all-new, highly compact 3.2L DOHC inline 6-cyl. that for the S80 replaces Volvo's longstanding inline 5-cyl. engines.

Production of the new 3.2L DOHC I-6 is scheduled to begin later this month at Volvo owner Ford Motor Co.'s engine plant in Bridgend, U.K. The second-generation S80 goes on sale later this year. (See related story: '07 Volvo S80 to Debut in Geneva)

The innovative I-6 optimizes performance with a unique cam-profile switching (CPS) system and a variable-intake manifold.

Ford's Bridgend engine-assembly plant, opened in 1980, currently builds V-6s and V-8s for Ford's Premier Automotive Group. Bridgend had produced nearly 12.5 million engines by the end of 2005.

All-new Volvo 3.2L DOHC I-6.

Although Volvo's new I-6 will be built in a Ford plant, Volvo's vice president of powertrain, Derek Crabb, insists the engine was designed and engineered exclusively by Volvo's powertrain department.

The 3.2L DOHC I-6 will be the new S80's standard engine; optional is Volvo's 4.4L 60-degree V-8, engineered and built by Yamaha Motor Co. Ltd. and first used in Volvo's XC90 cross/utility vehicle.

Fitment of the 311-hp, 325 lb.-ft. (441 Nm) V-8 means the '07 S80 is the first sedan in Volvo's history to have V-8 power. So far, sales of the V-8 in the XC90 have not met Volvo's targets, but the auto maker predicts sales of that engine will increase as S80 sales ramp up.

Meanwhile, the new I-6 hews to the same basic concept as the V-8. Its compact design simultaneously ensures the engine fits transversely while also maximizing the amount of crumple area in a frontal collision - a Volvo priority.

Volvo's engineers squeezed the dimensions of the engine into the most compact design possible: Crabb's team focused on a module that encompasses engine, transmission and ancillaries. Consequently, its dimensions are about the same as the current 2.5L I-5, Volvo engineers say.

Crabb says a compact design was a priority because of safety considerations.

“Volvo's engines are fitted transversely, and a compact engine has more space to move inside the engine compartment in the event an impact deforms the car's front end,” he says. “This helps reduce the risk of engine penetration into the passenger compartment.”

Locating the power-steering pump and air-conditioning compressor above the gearbox eliminates a front-end drive for ancillaries. Instead, a rear-located ancillary drive makes this possible. In addition, the alternator is direct-driven and installed on the engine block.

Volvo's engineers also designed the accessory drive system as a small gearbox with an intermediate shaft inside the drive shaft. The shaft-in-shaft design makes the very short package possible, including the elimination of the front accessory drive.

Different gears drive the two shafts to give them different speeds for the camshaft drive and ancillaries' drive.

In keeping with the desire to produce a compact package, the Volvo engineering team located a vibration damper inside the relatively long crankshaft of the engine. The internal viscous damper is a fluid type that's rarely used in passenger cars.

There are four valves per cylinder. The CPS system enables the dual intake-valve camshafts to generate two different valve lifts, depending on engine speed and load.

With normal throttle openings and low engine revs, fuel consumption is optimized. At the same time, the variable valve timing system and variable intake manifold combine to maximize torque to maintain good drivability.

For sporty driving with full throttle opening and high engine revs, valve lift and timing are adjusted to provide ample power at both low and high speeds.

Peak power in U.S. specification, says Volvo, is 235 hp, with 236 lb.-ft. (320 Nm) of torque. The current S80's 2.5L DOHC I-5 develops 208 hp and the same 236 lb.-ft. of torque.

The engine's variable intake system uses two flap-type valves to adjust intake manifold volume to help tailor engine load and speed to driving demand. The result, says Volvo, is a uniformly high and broad torque curve.

“Through precise interplay with the flap valves, we actually get three different torque curves that are integrated with one another,” Crabb says.

Made entirely of aluminum, the all-new 3.2L DOHC I-6 is larger than Volvo's last inline 6-cyl., a 2.9L unit that has been discontinued. The new-generation 3.2L I-6 is 44 hp and 41 lb.-ft. (56 Nm) of torque stronger than the previous 2.9L I-6, Crabb says.

“In principle, cam profile switching creates two engines in one,” he adds, saying the cam-profile switching design means the same engine can provide improved fuel economy along with better performance.

Mats O. Andersson, chief program engineer for the new 3.2L I-6, says the Volvo application of CPS is unique because it is applied to reduce fuel consumption in the low-lift mode. He notes that a CPS design was previously used by Porsche AG to boost power output.

Volvo says a higher-performance turbocharged variant of the new 3.2L I-6 can be expected in the near future.

The 396-lb. (180-kg) 3.2L inline 6-cyl. will meet U.S. Ultra-Low Emissions Vehicle-II and Euro 5 emissions standards, Volvo says. However, Environmental Protection Agency mileage figures for the new S80 with the 3.2L I-6 are not yet available.

In addition to the I-6 and the 4.4L DOHC V-8, Volvo says the '07 S80 also will offer another I-6.