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All-new Mercedes-AMG 2.0-litre breaks cover

Mercedes-AMG A45 scores up to 310kW/500Nm from world’s most powerful four-pot engine

7 Jun 2019


MERCEDES-AMG has finally unveiled details of its all-new 2.0-litre four-cylinder direct-injection turbocharged petrol engine that is destined to debut in the upcoming A45 4Matic hyper hatch.
Dubbed the M139, the twin-cam 16-valve unit with ‘Camtronic’ variable valve timing, two-stage fuel injection and a twin-scroll turbo with maximum charge pressure of 1.9 bar is tuned to deliver 285kW of power at 6500rpm and 480Nm of torque between 4750-5000rpm in its basic iteration, and a heady 310kW at 6750rpm and 500Nm from 5000-5250rpm in top-line S-model guise (with maximum charge pressure of 2.1 bar), making the 1991cc engine the most powerful production turbo four-cylinder engine in the world. 
This is up to 30kW/25Nm more than the previous M133 2.0-litre engine that Mercedes-AMG offered in its MFA transversely mounted modular front-wheel drive architecture models, as defined by the previous-generation A-Class. 
Like the latter, the newcomer has been specifically designed for the overhauled MFA2 platform that debuted with the existing (W177) A-Class in the middle of last year.
Along with the 2020 A45 4Matic, other initial recipients of the M139 are expected to be the upcoming CLA45 4Matic sedan and GLA45 4Matic compact SUV. 
However, it is understood that the imminent B-Class, CLA coupe sedan and GLB compact SUV are unlikely to receive the engine in the foreseeable future. 
According to Mercedes-AMG, the fresh two-pronged engine output strategy for the new four-pot turbo follows in the footsteps of the AMG V8 performance models that debuted with the existing E63 and E63 S versions in 2016, giving buyers a choice of powertrain to suit their needs.
The company claims leading response characteristics, as a result of the so-called “torque shaping” that creates the maximum outputs within the more natural driveability range of the engine, which is built by hand at Mercedes-AMG headquarters in Affalterbach in Germany.
“With this configuration, the AMG engineers have achieved a power delivery similar to that of a naturally aspirated engine for an even more emotive driving experience,” Mercedes-AMG said in a statement. 
“The engine developers were also able to realise a dynamically increasing torque curve in the lower engine speed range, thereby improving agility. The increasing torque at higher RPM makes the engine more free-revving.” 
Another factor in the development of the M139 was its innovative manufacturing processes, which involved, among other things, improved production processes to safeguard quality levels within what is a highly complex piece of engineering.
One key difference between the new engine and its M133 predecessor is the fact that the newcomer is rotated around its vertical axis by 180 degrees, resulting in the turbo and exhaust manifold shifting to the rear and the intake system migrating to the front, for a lower bonnet line and improved aerodynamics. Total engine weight is 160.5kg.
Furthermore, better exhaust gas flow is said to bolster torque response at both lower and higher revs, roller bearings have been integrated into the turbo for reduced friction and greater response speeds, the electronically controlled wastegate now operates more efficiently, ambient air now helps the turbocharger cool down (along with oil and water), there’s now an additional radiator behind the front wheelarch, the all-aluminium crankcase is now stronger than before helped by ‘closed-deck construction’ properties that boost rigidity while cutting mass, there’s a new coating process called Nanoslide technology to minimise friction between the pistons and cylinders, larger exhaust valves are fitted thanks to repositioned injection nozzles and spark plugs, and more efficient cylinder head cooling techniques have been developed.
According to Mercedes-AMG chairman Tobias Moers, the M139 is proof that the high-performance petrol engine still has a bright future.
“We already set the benchmark in the segment with the preceding engine,” he said. “This fundamentally new four-cylinder presented us with the challenge of doing even better. 
“And we succeeded with a number of sometimes revolutionary solutions. With the M139, we have once again impressively demonstrated the engine expertise of Mercedes-AMG. Not only is the output per litre unrivalled for a turbocharged engine, the high level of efficiency also demonstrates that the internal combustion engine still has further potential."

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