Break out the adenoids.
In this brave new world where AMG chases volume with 53- and 35-badged models, it’s easy to forget that the boffins at Affalterbach still employ very old-school processes to achieve the very best out of their cars. And while the smallest AMG cars like the A-Class (and derivatives like the CLA, GLA, and upcoming GLB) are usually not afforded such care and concern, it seems there’s been a change of tact among the decision-makers.
The prevalence of less potent, higher volume variants is likely why they’re splurging on the flagship A45 this time around. The still-unlaunched model is now in its ramp-up process ahead of introduction, and as part of that cycle, AMG’s letting some air out of the hype bag to talk about its all-important powertrain.
Questions have been asked about the necessity of a 45-badged A-Class since the A35 already offers up 225kW from its 2.0-litre four-pot, which is plenty potent for most. With a premium over that model, the 45s had better be a thing of engineering beauty which, AMG assures, it will be.
The all-new M139 engine is engineered to tolerances hitherto unseen in a road car, with both the 45 and 45S models set to benefit from race-derived innovations. In the 45S, all that work will produce an engine offering no less than 310kW and 500Nm, while the ‘lesser’ 45 will have to make do with just 285kW and 475Nm.
Salivating yet? Wait, we’re going to get geeky.
AMG has managed to achieve this by engineering a rev-happy mill that only derives forced induction from one scrolling turbocharger, which is an impressive feat within itself. The 7200rpm redline (!) means that AMG’s been able to engineer the M139 mill to deliver power & torque in a surprisingly linear fashion, though we remain skeptical about their claim that the engine behaves like a naturally-aspirated mill (we get you’re crack engineers, but you’re not magicians).
The M139 is very much a ‘bespoke for application’ sort of mill, a characteristic that AMG is very keen to point out. The distinction from the 4-banger in the A35 is most notable in terms of orientation, with a 180º turn in placement allowing for a more direct route for both turbo & exhaust for improved breathing. Additionally, the single twin-scroll turbo features a turbine-housing with dual flow pathways running parallel to each other which, working in conjunction with division ducts within the exhaust manifold, result in the negation of negative-influence from individual cylinders during heavy-load situations. The turbo also features roller bearings, reducing friction and therefore response times.
It’s not all about the turbo though, with the mill itself featuring multiple AMG innovations for maximum performance. It’s designed to work with an all-aluminium crankcase, a forged-steel crankshaft, and forged-aluminium pistons that cooperate with cylinders lined in Nanoslide coating. There’s also a port- and direct-injection system (alternating between driving conditions), and repositioned injector nozzles and spark plugs that make room for larger exhaust valves.
And with the ‘bang’ part sorted, it’s now time to talk about cooling. This highly-strung motor will feature an electric water pump that (notably) works totally independently of the engine, maintaining optimum operating temperature throughout. There will also be a secondary radiator which will act as a supplementary cooling system to the main radiator in the front, which to us speaks volume about the tolerances this mill is operating at.
It seems that the W177-generation A45 will live up to its status as a performance benchmark in the segment, carrying on the standards set by the previous-generation model. But with greater dynamic capability and improved technological innovation on board we must admit, this new-generation A45 will be one cracker of a thing when it debuts later this year.