POWERTRAIN
process, for example adapters in the valve control system.” The exhaust market has been undergoing change, according to Hall driven by exhaust legislation dating from 2019. “There’s always been a requirement for a better quality sounding exhaust,” he observes. “But there’s been a shift in the balance between customers wanting power and sound, to just wanting sound improvements.” Noise tuning is a very subtle
business. Hall explains, “What we do here depends on where the vehicle will be sold. Europe, China, America – the legislation is different in each market. For example, cars sold in the EEC area must emit no more than 2dB above stock specification, our modular design is more to enable us to be efficient in our production and stocking of exhaust systems. We aim to have as much crossover of parts between our different systems to ensure customers can easily change the exhaust configuration (if required) and for production efficiency. We rely on different silencer designs, resonated and non-resonated, and where OEMs fit valves into the exhaust we can redesign these to give a bigger sound differential.” Another ongoing trend which
directly affects the exhaust designer’s life is the increased use of forced induction. This offers some level of muffling within the turbocharger which has a knock-on effect for the silencer design. With its motorsport heritage, Milltek has an advantage here and despite access to the modern CAE tools, the company often bypasses this stage, preferring to jump to prototyping and physical testing early on. “On a new vehicle, we like the
real-world scenario rather than a testbed,” Hall confirms. “We will do rudimentary flow work but for the 90% of new-builds we will purchase a vehicle because it’s the fastest way to get the design correct. This aspect is important when dealing with common platforms such as a number of Volkswagen or Audi models where the silencer design and emissions side of it might be common to all, but the exhaust layout is not.” So, the majority of testing, whether it be for durability or performance, is
The new Milltek Sport performance exhaust for Gen 2 Yaris GR is now EC Approved
done either on the road or the track, with dyno work if necessary. Heat management is key here, measured both with standard OEM and additional sensors. It’s a subject that becomes acutely
important when dealing with hybrid vehicles. “We have been interested in hybrids for years,” says Hall. “Right from the base models up to Porsche Cayenne Turbo E-Hybrids, which we are currently doing development work on, in particular where sound is concerned. As it jumps from electric to engine power, the valve control in the exhaust is crucial here. We’ve
also worked with BMWs and JLR products, and when implementing a full system we spend a lot of time looking at heat management where there are large battery packs in the floor. Thermal wrapping and coating is something we do frequently with the higher power models. The job is actually getting easier as there’s more space now on some models due to additional sensors and also other aspects such as the installation of an Otto Particulate Filter (OPF) or Gasoline Particulate Filter (GPF) which may not have been there a decade ago.”
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