Lighter Materials Boost Panamera's MPG

With fuel economy showing up on even luxury-car buyers' radar screen and government regulations ratcheting upward the world over, it's no surprise Porsche AG engineers put as much focus on miles per gallon as performance in developing the new Panamera 4-door sedan.

The German auto maker says it employed lightweight materials, advanced powertrain technology and a few aerodynamic tricks to wring out an extra 4.4 mpg (1.9 km/L) on the way to a rating of 16/24 mpg (14.6-9.8 L/100 km) for the Panamera with its naturally aspirated 4.8L V-8.

The fuel-economy figures compare favorably with the 14/20-mpg (16.8-11.8 L/100 km) average for the much heavier Cayenne cross/utility vehicle with the same engine and are good enough to position the Panamera atop its class in carbon-dioxide emissions, at 253 g/km, according to the auto maker.

No Panamera, including the 500-hp all-wheel-drive Turbo, is subject to a gas-guzzler tax in the U.S.

At a backgrounder in Elkhart Lake, WI, for the new model — the first 4-door sedan in Porsche's history — Program Manager Stefan Ultsch details how the the 3,968-lb. (1,800-kg) car is able to squeeze extra miles out of a gallon of gas.

Among the biggest contributors to fuel efficiency is the Panamera's first-in-class 7-speed dual-clutch automatic transmission, Ultsch says. The DCT can be shifted manually, and a Sport-mode button on the center console changes the automatic shifts to a more aggressive pattern that holds lower gears longer.

But in standard automatic mode, the smooth-shifting gearbox allows the engine to work less, even at high speeds. In the Panamera Turbo model, the engine turns at just 1,200 rpm at a cruising speed of 124 mph (200 km/h). That's about 1,000 rpm less than its competitors, Ultsch says.

The Panamera also is first in its class with stop/start technology. Drivers can deactivate the system, but when engaged it's good for an extra 0.4 mpg (0.2 km/L) the engineer says.

Also making a difference is the coupe-like aerodynamic design, which Ultsch estimates at a plus 1.1 mpg (0.5 km/L). He says the standard model achieves a 0.29 drag coefficient, with the Turbo model only slightly worse at 0.30 due to wider wheels and bigger air intakes.

An underbody cover that stretches the width and length of the car and an adjustable rear spoiler help the Panamera slice through the air.

The spoiler deploys automatically at 56 mph (90 km/h). In Turbo models, it adjusts to a steeper angle to apply more down force on the rear axle at speeds above 127 mph (205 km/h). It also can be activated via a console-mounted button. Porsche says the Panamera is the first car in its class with “active aerodynamics.”

More efficient thermal management allows the V-8 to heat up quickly, resulting in a 1.1-mpg improvement, Ultsch says.

More exotic materials are employed to take weight out of the powertrain. Use of magnesium for the valve control box and cover cut 5.5 lbs. (2.5 kg), and aluminum for the camshaft adjusters trimmed another 3.75 lbs. (1.7 kg).

Aluminum bolts employed with all magnesium components and to connect the engine and transmission shaved 2.2 lbs. (1 kg). Porsche also thinned the walls of the intake manifold, saving 2.7 lbs. (1.2 kg). The block and head are made of aluminum as well.

The auto maker took more than 5 lbs. (2.3 kg) out of the crankshaft and connecting rods in the 4.8L V-8, compared with those in the Cayenne engine.

The base, rear-drive Panamera S V-8 gets a magnesium oil-flow housing that weighs 4.4 lbs. (2 kg) less than the aluminum component used in the AWD Cayenne and Panamera 4S.

The reduction in friction, alone, from the lighter-weight moving parts provides a 0.6 mpg (0.3 km/L) gain, Ultsch says.

Porsche also had to modify the Cayenne V-8 so it fits under the hood of the lower-profile Panamera. The oil sump is flatter than typical, and the driveshaft runs directly through the crankcase in AWD versions of the car.

Porsche specified lighter-weight material for the Panamera's chassis and body components, as well. Aluminum is used for the spring strut supports up front, the impact damper supports, front longitudinal arms and fender supports. Some rear body panels also are made of aluminum, as are the hood, doors, rear hatch and optional roof rack.

Door window frames are magnesium, while the trough in the luggage compartment is made of plastic.