DETROIT – To some powertrain aficionados, the sound of a whistling turbocharger pushing air through a small-displacement 4-cyl. engine is nothing more than an unpleasant whine.

Mann+Hummel USA Inc. has a new product to cancel out that turbo whine – at least for the driver.

At this week’s Society of Automotive Engineers World Congress here, the German supplier is exhibiting a compact, lightweight component soon to be marketed as the “symposer.”

The purely mechanical device, made up of four chambers, attaches directly in front of the throttle body. A movable flap senses pulsations generated when the engine vibrates due to acceleration.

As the flap moves, via a spring-mass system, it changes the high-frequency whistle of the turbocharger to the more muscular tone that is the natural byproduct of the combustion process.

That sound is carried through the outlet chambers of the symposer through the partition wall into the passenger compartment, through a sound pipe.

“You can attenuate the sound and make your engine sound like a throaty, high-performance V-6,” says John Baumann, manager-business development for Mann+Hummel.

Baumann declines to attach a price to the technology but says it costs significantly less than electronically controlled active noise-cancellation devices currently available.

This year, the symposer is standard on the ST sport version of the Ford Focus in Europe, powered by a 2.5L 5-cyl. turbocharged gasoline engine from Volvo Cars.

Mann+Hummel collaborated with Ford Motor Co. and DaimlerChrysler AG in developing the symposer.

Baumann says other auto makers are expressing interest in the device, although there are no other confirmed customers yet.

One drawback to the technology is that it has little impact on engine sound outside the vehicle. In addition, the sound is aimed more directly at the driver in the Ford Focus application, meaning other occupants in the vehicle are less likely to hear the lower-frequency sounds generated by the symposer.

Baumann says there is little chance for Mann+Hummel to sell the symposer on the aftermarket, as the device needs to be integrated in the intake tract during engine development.

Last month, Mann+Hummel made a significant move in the aftermarket, forming a 50-50 joint venture with Robert Bosch GmbH to acquire the Purolator filter business from ArvinMeritor Inc.

Both Bosch and Mann+Hummel produce air and oil filters for the European aftermarket, but Purolator instantly gives both companies a significant presence in the massive U.S. aftermarket.

Claude Mathieu, president and CEO of Mann+Hummel USA, estimates Purolator has about 20% of the filter aftermarket in the U.S.

Purolator has about 1,000 employees at its manufacturing plant in Fayetteville, NC, and recorded $267 million in sales in 2005.

The purchase closed last week, Mathieu says. ArvinMeritor has said it expects the Purolator sale to generate about $170 million in proceeds.

In other product developments, Mann+Hummel demonstrates a hydrocarbon trap that meets California Air Resources Board requirements for partial zero emission vehicles.

The device consists of a hydrocarbon absorptive media permanently installed in the vehicle’s intake manifold, usually above the air cleaner.

The media collects – or traps – all hydrocarbon fumes emanating from the intake system after engine shutdown and holds them until the engine is restarted, at which time the fumes are released in the intake stream and burned in the combustion process, Mann+Hummel says.

Hydrocarbon traps are required for vehicles to meet CARB’s partial zero emissions vehicle requirements, but Mann+Hummel says the component is cost-effective enough to include in a particular vehicle’s entire product range.

For instance, Mann+Hummel supplies the device to General Motors Corp. for the high-performance Cadillac STS-V but not for other STS models.

BMW AG’s all-new X5 cross/utility vehicle will offer Mann+Hummel’s hydrocarbon trap when production begins in late 2006 or early 2007.

tmurphy@wardsauto.com