Under the skin: Why the Lotus Emira’s four is more exciting than its V6 Car News

The well-known Toyota supercharged 3.5-liter V6 engine might be the obvious choice for many buyers of the new Lotus Emira, but the smart money could be on the alternative: the Mercedes-AMG 2.0 unit. turbocharged liters.

The M139 is Affalterbach’s last four-cylinder engine, and it is claimed to be the most powerful production turbocharged four-cylinder engine in the world.

In AMG applications there are two versions, one producing 382 hp and 204 lb-ft and the other delivering 415 hp and 369 lb-ft. cylinder engines. At these relatively conservative levels, the door is wide open for Lotus to tap more into the enormous potential of the AMG engine going forward.

Aside from pure performance, the attributes of an engine have a major influence on whether or not a car is fun to drive. The M139 spins freely at the top end, thanks to a torque curve that extends maximum torque up to 5,000 rpm in both AMG versions of the engine. It is also at high revs, with the red line at 7,200 rpm, and its manufacturer claims that its power output is similar to that of a naturally aspirated engine.

The design of the intake and exhaust system has a lot to do with this. The turbocharger is double scroll, which means it is fed from the exhaust manifold through separate passages, with two cylinders feeding each volute.

The advantage is quick low-end response combined with enough capacity to produce high power at the top end. The matching of the exhaust ports avoids the exhaust back pressure created by the presence of the turbo which hinders the scavenging of the exhaust gases from the engine. The compressor and loader turbine rotate in roller bearings that reduce friction and improve response when spinning up to a maximum of 169,000 rpm.

Elsewhere, the direct piezo injectors and spark plugs have been repositioned, leaving room to significantly increase the size of the exhaust valves (compared to those of the previous M133 engine), allowing freer passage of the exhaust gases. exhaust from the combustion chambers.

The engine also features two-stage injection, with a second set of solenoid-port injectors delivering additional fuel into the high-powered intake manifold. Some modifications have been made in order to install the engine in the Emira. Although still mounted transversely, it sits amidships and drives the rear wheels.

In AMG cars it has been rotated 180 degrees (compared to the old M133) to improve packaging. This places the exhaust and turbo in the rear, against the firewall, with the intake system up front in front-wheel drive AMG cars, but the engine has been adapted to fit the Emira with a new air intake system and a new exhaust system.

Sounds like a compelling package: This new, handcrafted engine could potentially be the best four-cylinder ever installed on a Lotus.

Extreme power density

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This notice was published: 2021-08-01 23:01:24

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