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Head-integrated exhaust manifold proves its point
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01/03/2007
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An advanced cylinder head with integrated exhaust manifold (IEM) has been revealed by UK car technology group Lotus Engineering, writes Roger Bishop. Designed for a three-cylinder engine, this latest IEM concept from the company is aimed at reducing emissions, weight and manufacturing costs on gasoline engines.
Lotus says integrating the manifold tracts into the cylinder head significantly reduces the parts count, saving costs throughout the development cycle and supply chain, from inventory and assembly to aftermarket supply.
Emissions reduction is achieved by locating the catalyst very close to the cylinder head which speeds catalyst light-off time by reducing exhaust gas heat loss. Overall engine heat loss reduction is achieved through minimising the surface area of the manifold by keeping the exhaust tracts within the head. In addition, the cooling jacket has been designed to retain heat in the engine rather than losing it to the engine bay. This accelerates warm-up to optimal efficiency.
Knock-on benefits include better HVAC performance, especially windscreen demist and passenger cabin warm-up efficiency.
The development is also claimed to improve engine durability by reducing thermal stresses. In particular, stresses usually associated with the interface of different materials – for example, where the cast iron exhaust and the aluminium cylinder head meet in a conventional design – are eliminated.
Lotus Engineering has already proved the concept to production readiness in demonstrator programmes. Data gathered suggests that for a typical DOHC 16-valve 1.6 cylinder gasoline engine, an IEM has potential to reduce build cost by up to 5%, reduce catalyst light-off time by up to 20% (+5s) and reduce powertrain mass by around 5kg.
Geraint Castleton-White, head of powertrain at Lotus Engineering, said: “Two key drivers for OEMs are cost-down and reduction of CO2 emissions. Our IEM technology brings to a practical reality an established principle that has been very challenging to implement in production.”
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Author
Roger Bishop
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