Lotus Engineering displayed their Integrated Exhaust Manifold technology at the 2007 Geneva International Motor Show. Basically, it is an exhaust manifold integrated into the cylinder head. A demonstration of this was shown as a cylinder head design for a small 3-cylinder engine, which I would say would benefit much from this technology. Integrating the exhaust manifold into the cylinder head brings numerous benefits which I will outline below.
An integrated exhaust manifold reduces parts count, which reduces costs throughout the development cycle. Other areas where this will reduce costs include the inventory, assembly and aftermarket parts supply areas. Less parts, less to stock.
Through the use of a cooling jacket design, heat is retained in the engine (which is cooled via the radiator system) rather than letting it radiate into the engine bay. This improves the performance of the air conditioning system, thus reducing it’s power consumption. A cooler engine bay also means cooler air into the air intake, which boosts performance. The engine also warms up more quickly. Coolant can also cool the engine more evenly, reducing engine block stress.
Engine durability improves, as thermal stresses usually occur at points where different materials meet. In an engine with a conventional exhaust system design, an aluminium cylinder head meeting a cast iron exhaust causes thermal stress.
The integrated exhaust manifold also allows the catalytic converter to be positioned very near the exhaust output, thus reducing the amount of exhaust heat lost in travelling from the cylinder to the catalyst. This improves catalyst performance, thus reducing emissions to an ultra-low level without incurring higher costs.