To most motorists, the exhaust is merely a length of steel pipe weaving its way from one end of the car to the other. And yet in the last few years the humble exhaust system has become a technology hotbed, playing a decisive role in controlling emissions and acoustic comfort. Matthew Beecham reports.
Technical developments in the hot-end of the exhaust (i.e. the section closest to the engine, linking the manifold, catalytic converter and particulate filter) are highly influenced by the new emissions legislations. Consequently, we are seeing the emergence of new exhaust system technologies for both petrol and diesel engines.
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As each new emissions regulation swings into force, more and more content is added to the exhaust in order to comply. This adds value to the overall price of the system. Manufacturers estimate that the average price of an exhaust system for a diesel light vehicle could quadruple when Euro 4 emission standards come into force. Although Euro 5 standards have yet to be agreed, manufacturers believe that the cost of the complete exhaust system could double again when the regulations are introduced
Forthcoming stricter emissions regulations throughout the world will, therefore, significantly increase demand for automotive catalysts and many diesel-powered vehicles will need to be equipped with diesel particulate filter (DPF) systems at the factory. With diesel vehicles now exceeding 40% of European new car sales, consumers are changing their opinions and perceptions of, diesel engines. “The negative reputation of old diesel engines has been completely supplanted, and the new generation after-treatment systems are providing the solution to the emissions issue,” said Michael Bleidt, vice president and general manager for ArvinMeritor’s Light Vehicle Systems’ Air and Emissions Technologies at a recent technical media briefing entitled ‘Breath Easy – the Solution is on the Horizon’. “Compared to a gasoline engine with the same specific power (kW/kg), a diesel engine has approximately 20% less fuel consumption and around 10% lower CO2 emissions.”
A particulate traps (or collects) soot particulates flowing through the exhaust and burns them off periodically. Cars fitted with these filters have been proven to produce 10,000-times fewer particulates than cars without the filters. By 2009, manufacturers predict that more than 12 million vehicles will need to be equipped with DPFs in order to conform to mandated exhaust emission values. As one of the leading manufacturers of DPFs, ArvinMeritor currently supplies more than ten OEMs. The company says confirmed new orders are driving a strong increase in production, with 2007 annual production estimated to exceed 1 million units for the first time.
While new emission norms spell out good news for suppliers, there are signs that they are being stretched, as John Fuerst, Business Line Executive, Exhaust, Delphi Energy & Chassis, said: “Although we see a huge market for this type of filter, the supply side is already struggling to keep up with demand. In addition, there are a lot of questions regarding which filter technology will eventually dominate.”
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By GlobalDataTurning to catalytic converters, the oscillating price of certain precious metals used in manufacture has triggered some novel innovations. Last year, Delphi launched its new FlexMetal catalyst system onto the US and European markets. The technology uses advanced alumina and oxygen storage components, which improve exhaust gas diffusion and catalytic activity over a wider air-to-fuel ratio, but crucially requires the use of far less precious metals than normal. For some applications currently in production, Delphi says precious metal savings of 40% could be made by using the new technique. The new FlexMetal line also offers higher temperature durability and faster light-off. The production process also allows customers to make changes in precious metal content late in the design stage, without major modifications to other washcoat components, so they have more flexibility in buying the metals and hence better chance of getting them at lower prices. “Buried in the FlexMetal technology lies improved base metal structures that improve the interaction between the noble metal and the exhaust stream,” added Fuerst. “That results in better and more efficient catalytic conversion while lowering noble metal requirements.” Delphi has also developed a number of new process technologies, including Precision Metal Addition. “PMA is a state of the art process to precisely control the metal that is put onto the catalyst. The more controls that you have on the noble metal addition, the less excess metal is applied so the more cost effective you can be.”
Emitec, the German catalyst manufacturer founded in 1986 as a joint venture between Siemens and GKN, generally has a low profile, but has nevertheless become one of the biggest catalyst manufacturers in the world, employing over 800 people in Germany and the US. Its success has been built on its pioneering work building catalytic converters with metal substrates. One of its latest inventions is a pre-turbo catalyst for diesel engines that makes use of the higher exhaust gas temperatures found before the turbocharger. The company is especially interested in the challenges of emissions reduction for diesel engines and sees major business potential there, both in Europe and eventually the US. Emitec is also working on emissions reduction for HCCI engines. Dr Joachin Diringer and Verena Vogel of Emitec told us: “We started production of catalysts with structured foils, so called TS-Design, in 1994. Next generation of catalysts are creating turbulent flow. The turbulence means that the pollutant molecules will – with increased probability – reach the active centres of the catalytic coating containing precious metals. … When HCCI engines are introduced, Emitec will have the new tubulent substrates ready to support this system.”
While most emissions control system development work has centred on the hot-end of the exhaust, there are many opportunities at the cold-end for manufacturers to enhance their systems and increase the value added. “The cold-end will be affected by the probable arrival of 71dB legislation and fuel consumption reduction,” said Mauro Occhetti, marketing and sales director for Magneti Marelli Exhaust Systems. “This will result in more complex systems and acoustic solutions, like dual mode mufflers. The trend of increased warranty periods will lead to widespread use of better stainless steels, although with reduced thickness.”
Bosal believes that the major driver of innovation in the cold end of the exhaust is weight reduction. “Steel prices are still high. That makes it difficult to reduce the price. Consequently, we have to look at ways in which to reduce weight. The problem is that the added emissions technologies at the hot-end simply increase weight,” said Ad Ham, managing director of Bosal Automotive Europe. “It is an interesting challenge currently driving innovation.” Bosal’s lightweight complete exhaust system is the result of a return to first design principles, and consists of fastening each exhaust system component independently to the car, with very little relative movement. Such a system no longer needs to be self-supporting, so can be made thinner and lighter, while a new mechanical device de-couples the system from the engine, reducing vibration by a factor of 10. “Our lightweight exhaust concept has been accepted by some carmakers but not in its entirety,” added Ham. “If the whole concept were applied to a vehicle, it could reduce weight by 40-50% compared to a conventional exhaust system.”
Turning to the exhaust system aftermarket, the outlook is still gloomy. The useful life of exhausts has been extended mainly thanks to the notable switch in materials used to produce the pipes. In 1984, vehicle makers began to demand that the exhaust should be made from stainless steel instead of aluminium. Today, the use of stainless steel in exhaust systems is approaching 100%. “Most newly-registered vehicles in northern Europe come equipped with a stainless steel exhaust system,” said James Hodgson, technical manager, Aluminised Products, Corus Strip Products UK. “That system will typically last 6 – 7 years. But in southern European countries, because of the indigenous climate, OEMs tend to use more aluminised steel in exhaust manufacture.”
Consequently, manufacturers continue to forecast a shrinking exhaust aftermarket. “We expect a decrease of approximately 5-8% this year, and then slowing,” said a spokesman for Eberspacher. “We believe that the global exhaust aftermarket is declining by 4 – 6% each year,” said Alex Gelbcke, manager of Tenneco Automotive’s European emission control aftermarket business. “But this does not mean that Tenneco Automotive is following the same trend. We are gaining market share. We are grabbing new business. Our sales are up in many regions.”
On balance, the automotive exhaust market has grown in importance, driven by the emphasis that is now placed on emissions control worldwide. What was once a relatively simple product has become increasingly complex and more expensive.
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