Under the skin: Why the Lotus Emira's four is more exciting than its V6
The Lotus Emira’s M139 engine is hand-built by Mercedes-AMG on a ‘one man, one engine’ basis
The familiar supercharged 3.5-litre
Toyota V6 engine might be the obvious choice for many buyers of the new
Lotus Emira, but the smart money could well be on the alternative: the turbocharged 2.0-litre
Mercedes-AMG unit.
The M139 is the latest four-cylinder engine from Affalterbach, and it is claimed to be the most powerful turbocharged four-cylinder production engine in the world.
In AMG applications, there are two versions, one producing 382bhp and 204lb ft and the other delivering 415bhp and 369lb ft.
Lotus quotes the power output of the Emira “across the range” as being between 355bhp and 395bhp, encompassing both V6 and four-cylinder engines. At those relatively conservative levels, the door is left wide open for Lotus to further tap into the AMG engine’s huge potential in the future.
Sheer performance aside, an engine’s attributes have a major influence on how thrilling a car is to drive, or not. The M139 is free-revving at the top end, thanks to a torque curve that extends maximum torque up to 5000rpm in both AMG versions of the engine. It is high-revving, too, with the redline at 7200rpm, and its maker claims its power delivery is similar to that of a naturally aspirated engine.
The design of the induction and exhaust system has a lot to do with that. The turbocharger is twin-scroll, which means it is fed from the exhaust manifold through separate passages, with two cylinders feeding each scroll.
The Lotus Emira’s M139 engine is hand-built by Mercedes-AMG on a ‘one man, one engine’ basis
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