In some ways, Ron Buchler and Steve Patteson act more like detectives than truck component engineers. As senior engineer for Walker Exhaust Systems, heavy-duty division, Buchler focuses on older truck models instead of the ones being developed for the future. He spends a lot of his time out in the field, studying exhaust systems on older vehicles and plotting how to create cheaper replacement components.

“Most of our focus is backwards,” he says. “We try to predict what will happen to a truck when it gets into the six- to ten-year life range. We want to determine which replacement exhaust parts it will need and how we can design the package to fill that need.”

Buchler must also use his exhaust-system divining skills on a wide range of vehicles: Class 3-8 tractors, straight trucks and school buses. But while he focuses predominantly on design issues, other factors are never far from his mind, especially cost.

“Price remains the biggest issue for aftermarket exhaust system parts,” he points out. “It's always at the top of the customer's list. Appearance is next. People pay a lot of money for their trucks, so they want those exhaust stacks and mufflers to look good. Finally, the components have to be lightweight.”

Patteson, formerly chief engineer for Walker's heavy-duty division and now manager of marketing products, adds that Walker has to develop its aftermarket packages without the benefit of heavy R&D funding.

“As an aftermarket supplier, we must produce price-conscious product packages. We also need to make the parts easy to ship and store — for the warehouses, as well as the fleets,” Patteson says.

Aftermarket exhaust suppliers also have to make sure their products fit a broad range of vehicles that have become very specialized over the last two decades. “It's a challenge for us engineering-wise; trucks have become more aerodynamic and distinct even within the same family,” Patteson explains.

Buchler points out that “every pipe bend and clamp put into an exhaust system adds cost. So we must build the replacement package with less complexity, yet not affect the system's form and function on the truck.”

Materials are another challenge. “The interesting thing about exhaust systems is that the more they are used, the less corrosion they suffer,” Patteson explains. “Corrosion is a direct result of both acidic exhaust gas and chloride residue from road salt condensing on the exhaust system components. If the truck is running, the heat from the exhaust keeps the system dry, clean and corrosion-free.”

Aftermarket suppliers initially worked with parts coated with zinc to minimize corrosion, but found that if a truck's exhaust temperature exceeded 500 F, the zinc would be “burned” off, exposing the steel to corrosion. Stainless steel isn't a viable option because of its high cost.

Engineers finally settled on aluminized low-carbon steel. The aluminum coating can withstand the effects of chloride, as well as exhaust temperatures up to 1,400 F, while the low-carbon steel base keeps costs down.

Buchler and Patteson agree that one of the primary challenges in the future will be constructing exhaust-system replacement part packages for 2007-model trucks, as extensive aftertreatment systems designed to reduce diesel engine emissions are expected to complicate exhaust system design.

“The price of such systems and the cost to manufacture unusual exhaust-system components could change things,” Patteson says. But that issue is farther down the road for aftermarket engineers than for their OEM counterparts. “Right now I'm focusing on aftermarket exhaust packages for '98-'01 trucks,” he says. “I have awhile before I have to turn to '07 models.”

Name: Ron Buchler, senior engineer, Walker Exhaust Systems (subsidiary of Tenneco Automotive), heavy-duty division.

Background: Joined Walker 1962; has been senior engineer, heavy-duty product line, since 1988.

Name: Steve Patteson, manager of marketing products for Walker.

Background: B.S., automotive technology, Kansas State College. Joined Walker in 1976, taking on chief engineer role in 1996, responsible for product design. Promoted to current position in 2000.

Each month this column looks at emerging truck technology issues through the eyes of a leading engineer.