Detroit 2012: What makes a Bentley V-8 different than an Audi V-8?

Bentley’s 2012 Detroit auto show reveal of the Continental GT V8 presents a new, downsized reality for the exclusive British automaker, but this wasn’t our first time seeing the twin-turbocharged, 4.0-liter V-8. The same core engine is already under the hood of the Audi S8, a car we drove late last year. While Bentley’s application is extremely similar to that powertrain, the ultra-premium marque has clearly made some tweaks to the engine. We sat down with Rolf Frech, Bentley’s board member in charge of engineering, and Brian Gush, director of chassis, powertrain, and motorsport, to learn how the company tuned the engine to downsize the brand's engines without downgrading its reputation.

Most apparent in the differences between the S8 and Continental engines is the difference in output ratings. Bentley trades power for torque in the eight-cylinder Continental GT with a rating of 500 hp and 487 lb-ft of torque compared to 520 hp and 479 lb-ft in the S8. “We tried to give it a Bentley feeling,” said Frech. “Bentley means, of course, torque. You have to have the torque in a really wide range.”

Since Bentley and Audi collaborated on the engine from the start, both companies were able to specify their requirements for the engine. That means that brands can use the same hardware save for the intake and exhaust plumbing. The engine design accounts for variances between nameplates like unique engine mount locations and while Audi uses an electronic oil level sensor, Bentley can retain the time-honored dip stick.

Both the Audi and the Bentley utilize cylinder deactivation, running on just four-cylinders when cruising at low load thanks to technology that  Bentley brought to the table. The British marque honed its competency on cylinder deactivation with the Mulsanne sedan, but the brands took different approaches to managing the corresponding noise and vibration that comes with four-cylinder operation. Audi utilizes active noise cancellation to silence the engine’s undesirable frequencies and active engine mounts pulse to counteract the imbalances created while running in four-cylinder mode. The Bentley engine mounts are far less complex, with two-stage, adjustable firmness to dampen vibrations in a far more traditional manner. During idle and at certain engine loads, the engine mounts switch to their softer setting to keep undesirable vibrations from reaching the cabin. Bentley also passed on active noise cancellation.

The engine couldn’t be fired up on the Detroit show stage, but our European bureau chief has already driven the Continental GT V8 and describes the engine note as far more seductive than the S8’s growl. While the Audi’s active exhaust changes with the driver-selectable engine setting, the Continental’s exhaust valves are only controlled by the engine management logic. “With the V-8, we try to get a real V-8 sound. You have to hear every cylinder,” said Frech. “We tried to get a little bit more aggressive than a W-12 engine.”

For full driving impressions of the Bentley Continental GT V8, read Georg Kacher’s first drive.

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