Systems approach to NVH reduction

Rieter Automotive's Rieter Ultra Light dash insulator has a mass of approximately 12 lb (5 kg) less than a traditional dash insulator that uses foam-backed rubber or asphalt to deaden sound transmission.

Talk of double-digit weight savings and drops in interior noise level gets the attention of customers. Backing up the claims translates to business.

"We have the ability to make cars lighter, quieter, and more fuel efficient, and we accomplish that by taking a total vehicle approach," said David Westgate, President and CEO of Rieter Automotive Systems' Business Group Americas. "We're able to do all three at the same time (whereas) a lot of companies can do lighter, or quieter, or more fuel efficient, but not all at the same time."

One example of the systems approach is Rieter Ultra Light. When it debuted on a 2000 model year vehicle, the acoustic-management concept was applied to a single component. In contrast, the 2002 model year Lexus ES 300 uses Ultra Light on the dash and flooring. The acoustic and weight savings result possibilities are impressive.

"With our Ultra Light technology we're able to take out somewhere in the range of 15 to 90 lb per vehicle," said Westgate, or "an average of 30 lb per vehicle, and improve the acoustic performance. Ultra Light is basically a complete paradigm shift of how you handle noise within a vehicle. And we've never, ever failed," he said, referencing 50 various vehicle demonstrations as well as production applications ranging from sedans to pickup trucks and SUVs powered by gasoline or diesel engines.

The conventional approach to noise repression is insulation. "Rieter Ultra Light is replacing heavy insulators with light, highly absorbing constructions," said Jeff VanBuskirk, Vice President of Systems Engineering & Development for Rieter Automotive North America, Inc., in Farmington Hills, MI. In simple terms, the lightweight, fibrous Ultra Light absorbs and dissipates sound energy.

"We think that the 30 lb average is a drop in the bucket (vs.) what we can do if we get the (bumper-to-bumper) acoustics integration foresight and thought right up front on the vehicle design," said Westgate. Ultra Light is produced for the North American market at facilities in Indiana, Ohio, and Ontario, Canada. A Tennessee plant comes online in January 2003.

David Westgate, President and CEO of Rieter Automotive, Business Group Americas (left), and Jeff VanBuskirk, Vice President of Systems Engineering & Development, Rieter Automotive North America, stand in front of a Rieter Underfloor Module. This system pictured is based on the module used on the Mercedes A-Class in Europe.

Rieter is also touting a list of benefits associated with its underfloor module. "It's designed to manage underfloor space relative to aerodynamics, thermal (properties), and acoustics," said VanBuskirk. "We haven't re-invented the wheel, but we've re-invented how we look at the wheel."

A two-piece underfloor module presently is used on the Mercedes-Benz A-Class sold in Europe. The North American market is slated for a production application of a full underbody module in the 2005 model year.

Average improvements with a vehicle using a tailored underbody module reflect a 10% aerodynamic upgrade. "This is equivalent to a (mass) savings of 250 lb in terms of fuel efficiency," said VanBuskirk. There are also acoustic impacts. For example, during wind-tunnel testing on a minivan fitted with an underfloor module, a 12 dB reduction occurred inside the vehicle. The module can be designed as a one-piece, ready-to-install unit, and all service ports are hinged for service technician access.

Rieter, founded in Switzerland as a textiles company 207 years ago, is in high-growth mode with its automotive business, presently at $600 million. Westgate expects business to double in four years and reach between $2 billion and $3 billion in eight years. "We'll have many introductions for the next few years," said Westgate. "We're also stepping up the activity in R&D to further enhance that."

- Kami Buchholz

Air suspension advances

Air suspension is being found increasingly in automotive products, notably for large, up-market cars, but the technology is likely to cascade to other classes. Land Rover's new Range Rover uses air suspension to maintain appropriate ride height regardless of load, with computer control providing automatic, optimized ride height for differing driving conditions, including off-road. Air suspension enhances off-road ability by providing considerably greater wheel travel—300 mm (11.8 in) for the Range Rover—independently to each wheel than can be accommodated by steel springs.

The challenge for designers of any 4x4 SUV such as the Range Rover is the reduction in the inevitable compromise between on- and off-road-suspension performance. To achieve this, Land Rover worked with Delphi in Europe to develop an airstrut module that would meet particularly tough ride and handling criteria. For the Range Rover, Land Rover required very long suspension travel with precise wheel control and low friction. The solution was to use a module from Delphi that includes a MacPherson airstrut in which the airspring, set at an angle to the damper, provides side load compensation to enhance durability and improve ride quality.

According to Delphi, side load compensation has not previously been possible with air springs due to the additional stresses it imposes on the airsleeve. To overcome this factor, Delphi worked with a specialist supplier to develop a new, exceptionally strong airsleeve material that uses a rubber composite with aramid reinforcement. Land Rover also set tough targets for the allowable deflation with time, aiming for only minimal drop in vehicle height over several weeks, even when fully loaded.

Delphi then developed a new manufacturing process that allows the airsleeve to be manufactured around the damper to virtually eliminate potential leak paths. The process has been validated using a new environmental test system that cycles modules through a lifetime of severe use in temperatures from -40 to +100°C (-40 to +212°F). The same system will be used for ongoing process checks, while every strut will be subjected to an inline, 1000-kPa (145-psi) air-pressure test.

The complete Delphi module includes the airspring, a twin-tube gas-charged damper strut, the top mount, and an integrated radial bearing of a new, durable design. With a 28-mm (1.1-in) solid rod and a 65-mm (2.56-in) damper tube, it is thought by Delphi to be the largest automotive strut/damper module ever produced. The airstrut module is being manufactured at Delphi's Luton plant, which is north of London.

- Stuart Birch