Although using engines that, in the words of TRD's Lee White are "rooted in 1960's architecture", much about NASCAR is right up to date, employing modern design trends and manufacturing methods. NASCAR appeals to a specific audience, who are perhaps less technically motivated than those who follow MotoGP or Formula One, yet it attracts and retains a lot of the very best engineers in racing - precisely because of the technical challenges that the pushrod V8 engines present.
When it comes to exhaust manufacture, NASCAR uses much of the same advanced manufacturing technology and materials as Formula One. NASCAR exhaust development places a lot of demands on exhaust manufacturers, some of these report that NASCAR is the one series that stands out due to the amount of exhaust development carried out.
High-temperature materials, such as Inconel are not as popular in NASCAR as they are in some other series such as Formula One where high-temperature materials are universally used for exhaust systems. It is reckoned that approximately half of the Sprint Cup teams still use stainless steel, despite the fact that there is a slight weight penalty compared to Inconel. The strength and durability of Inconel means that it is possible to manufacture exhaust systems in impressively thin sections. In order to keep stainless exhausts competitive against these systems, stainless materials need to be pushed to their limits on wall thickness, sometimes using material as thin as 0.028 in thick, although 0.035 in is more common. Durability is a concern for NASCAR exhausts, and teams are trying to get exhaust designs that can run comfortably for 3,000-5,000 miles. The lack of availability of tube in the desired combination of diameter and thickness demanded by the various teams means that exhaust suppliers often manufacture much of their own tube, even though this requires investment in expensive equipment. Where Sprint Cup teams use Inconel and have an affiliated Nationwide team, some Inconel systems are 'passed down', but non-affiliated teams who have to purchase new systems generally specify stainless steel materials.
With long races in NASCAR Sprint Cup, exhaust durability is very important as the next opportunity to check an exhaust system might be more than 500 miles away. A lot can happen in 500 racing miles, so quality has to be 'built in' to each exhaust, with careful quality control procedures being very important.
With engineers from the NASCAR teams pushing development, exhaust manufacturers need to keep track of the latest developments in manufacturing technology. It often isn't possible to have the very latest technology owing to the costs involved, and keeping an eye on the maturity of new manufacturing technology and the costs of introduction mean that NASCAR exhausts employ new technology which represents real value.
Away from manufacture and looking to design, the advent of 3D CAD systems means that some suppliers are able to design and manufacture a NASCAR exhaust without having sight of the engine or car. If teams can supply accurate CAD data for their car, the exhaust can be designed 'remotely'.
Fig. 1 - These Inconel exhausts are destined for use in NASCAR, although not all teams have adopted this material (Courtesy of PRO-FABrication)
Written by Wayne Ward