Jaguar uses sound technology for 'quiet' ride

By Tony Lewin, Automotive News

Coventry, UK-Jaguar Cars Ltd is using active engine mounts for its diesel-powered XJ sedan, developed by British supplier Avon Rubber plc, and says these units cancel 90 percent of idle vibration, a frequent source of irritation on diesel cars.

Jaguar, a unit of Ford Motor Co., is also using sound-deadening technology it developed with suppliers to provide its new with "world-class smoothness and quietness."

The Jaguar XJ 2.7-liter diesel is the first production car to use Avon Rubber's Vibramount technology. The technology internally generates pressure waves that counter engine movements exactly to eliminate vibration and noise.

Avon has worked on active engine mounts since the late 1990s. It also is developing applications with other auto makers, said business development engineer Mike Lines.

Jaguar credits an innovative sound pack from German supplier Carcoustics International GmbH and acoustic laminated side glass from Sekurit Saint-Gobain of France.

The XJ is Jaguar's first diesel in the upper-premium segment and is designed to compete with diesel models from higher-volume German competitors, such as the Mercedes S class, BMW 7 series and Audi A8, the firm said. "We wanted the XJ V-6 diesel to match the V-6 gasoline model for interior noise at idle," according to Dave Mitchell, programne chief engineer.

The raw noise emissions of the diesel engine at idle are three times greater than those of the gasoline V-6, he said. A key goal was eliminating noise in what Jaguar calls the "cackle region," full-throttle engine loads between 2,000 and 4,000 rpm, Mitchell said.

Working with Carcoustics, Jaguar developed an under-the-hood sound pack that met noise goals and was 20-percent lighter than the gasoline model.

The package includes a double bulkhead liner, tunnel liner and insulation in the engine compartment sides and wheel arches. The fiberglass hood liner has integrated seals to close all gaps and prevent the escape of radiated noise.

It also has a multilayer, undertray seal under the vehicle that uses acoustic materials similar to those in sound-deadening chambers, Mitchell said.

Roland Bischoffs, Carcoustics' marketing chief, said Jaguar's specifications for the diesel XJ were challenging.

"The target was superior acoustical comfort: the dynamic of a high-powered diesel and the absence of any diesel-specific noises," he said. "The package was developed with substantial support from our tech centre in Leverkusen, Germany."