Titanium affords a long-life mufflerTitanium affords a long-life muffler

Detroit-"That's ridiculous," was the reaction of one engineer to whom I mentioned that the 2001 Corvette ZO6 is equipped with a titanium muffler (two mufflers to be exact). He scoffed mainly because he felt use of the metal was more appropriate for gold-plated cache-like composite watchcases-rather than something truly useful.

But such attitudes toward titanium, even among engineers, are no longer warranted, according to Kurt Faller, director, international automotive applications for Timet (Morgantown, PA), the major worldwide producer of the metal for the corrosion resistant materials market. While titanium is more expensive than stainless steel used in current high-performance mufflers, it is about half the density (with the same strength) and virtually impervious (see table). And in processing, the same basic steel fabrication methods can be used, with adjustments, say to forming rates.

But not the least important, because of recent agreements between the company and its traditional customers, the price has stabilized-users have agreed to certain order levels independent of market conditions in return for a steady price regardless of order ups and downs, notes Faller. Such stability, he adds, will allow supplying titanium to non-aerospace industries, such as automotive, that are more sensitive to price.

Using titanium, as with ArvinMeritor's (Troy, MI) Corvette exhaust, the customer gets a muffler system that may never need replacing due to corrosion (it is warranteed for 10 years). A stainless steel muffler can last just five to seven years. In addition, because deterioration is minimal, it is completely recyclable. Another green benefit: With lighter weight (26 lbs) than the equivalent steel exhaust system (44 lbs), overall gas mileage will increase, as if that is a concern when driving a 'Vette. For larger cars, such weight savings may be upwards of 40 lbs, according to Faller.

When asked the reasons for going to the titanium exhaust, Zoltan Varga, a GM design release engineer working on powertrain hardware, says with the ZO6 package for the Corvette, "It's a high-performance machine geared for the racing enthusiast, so the obvious answer is mass reduction to increase power-to-weight ratio." He also notes that durability in the race-track environment of high g loading and temperature was another key requirement-and that "the muffler system passed a 50 hour test at 10g load and 1,245F temperature, simulating the 24-hr race environment," a test not usually done with a stainless steel muffler. And Varga says although there may have been some concern at the adoption of a titanium system, "now that it is in production, scrap rates and tool life are comparable to working with stainless steel."

* Source: Timet

**Engineering Materials by Kenneth Budinski

***But a titanium system is half the weight, and in certain applications, a thickness allowance for corrosion needn't be added, so the price difference is below the resulting 5xcost penalty.