Integrated exhaust

Lotus Engineering has designed a cylinder head with an integrated exhaust manifold (IEM). The production-ready design, it says, can significantly reduce manufacturing costs, emissions and weight on most gasoline-engined passenger vehicles.

The cylinder head, for a small 3-cylinder engine, is the latest of a number of IEM designs developed by Lotus Engineering as part of its consultancy business.

Following its development programmes, the UK automotive engineering consultancy estimates that for a typical DOHC 16-valve 1.6 cylinder gasoline engine, an IEM has potential to cut up to 5% of the total build cost, reduce catalyst light-off time by up to 20% (approx five seconds), reduce powertrain mass by up to 5 kg as well as improve engine durability.

By integrating the manifold tracts into the cylinder head, the parts count is reduced significantly, 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 reduces exhaust gas heat loss upstream thereby cutting the catalyst light-off time. The reduction in overall engine heat loss is achieved through minimising the surface area of the manifold by keeping the exhaust tracts within the head. Through intelligent cooling jacket design, heat is retained in the engine rather than lost to the engine bay, accelerating engine warm-up so it more quickly reaches optimal efficiency. This also benefits the HVAC performance, reducing windscreen demist and passenger cabin warm-up periods.