Donaldson silences engine-brake bark

NASHVILLE, Tenn. (March 25) — Towns and cities across the continent will be happy to know that there’s now a way for trucks to keep the peace. The new ‘Silent Partner’ from Donaldson Company is a muffler designed expressly for use with engine brakes, developed in co-operation with Jacobs Vehicle Systems, which supplies 90% of those brakes. It’s claimed to produce just half as much exhaust noise during engine braking as a conventionally silenced truck, and 25% less acceleration noise — inside and outside the cab.

The new muffler also changes the nature of an engine brake’s staccato “bark,” turning it into — believe it or not — an almost mellow tone. It’s an issue of growing importance as governments of all sizes seek to control truck noise in general. Some 70% of heavy trucks have an engine brake installed, and 90% of new ones are spec’d that way.

Donaldson guarantees the Silent Partner for eight years or — and this is a first — one million miles. The engineers did that distance in testing on both open road and closed track, along with some very sophisticated lab work. That included the manipulation of the frequencies of an engine brake’s sound. The human ear is most annoyed by pulsating sounds at high frequencies, so Donaldson “tuned” the noise, the first time a truck muffler has had that treatment.

The new stainless-steel muffler is a bolt-on replacement for existing units. It does not increase back pressure or reduce fuel efficiency, says Ric Canepa, Donaldson’s director of business development. It will cost more than an ordinary muffler, with a list price of US$499, but it should also last considerably longer, he says.

Does it work? Herman Miller, director of maintenance at a major U.S. private retail fleet, says yes after installing the mufflers on three trucks last October as a test. “The ‘bite’ of that exhaust noise is gone,” Miller says. “The difference, truthfully, is like day and night.”

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