Designing stainless exhaust systems

Abstract

With the ever-increasing price of automobiles, durability and reduced operating costs have become major concerns in North America, Europe, and Japan. In the US, the exhaust system was once thought of as disposable every 3--4 years, but it is now considered a nonreplaceable item for at least 5--7 years, the average time an initial owner keeps a vehicle. Through the mid-1980s, the only stainless steel on most US car exhausts was the downpipe and catalytic converter, and these were due to government warranty mandates. Today, most US passenger car exhaust systems are almost entirely stainless steel, and with the 1996 model year switch of GM light trucks, the average use of stainless alloys in US vehicles will exceed 23 kg per vehicle. The US experience with stainless has shown that certain design considerations can further increase system life and reduce manufacturing problems. Such considerations may also benefit the European situation, which has seen an increase in the use of stainless alloys in exhaust components since tighter pollution laws began taking effect in 1990.