Mercedes Benz Previews Wild A45 AMG

By James Mackintosh, 15 June 2012

The new Mercedes-Benz A-Class will be here soon, making it's first trip over to the United States since the model's debut back in 1997.  It's been drastically recast from it's original image as a tallish MPV into a more mainstream shape, to include a pretty 3-door hatch as well as a small sedan.  This is all good, but what's really interesting is the upcoming AMG version.

AMG has never had an official version of the A-Class before, but that's set to change with the third generation model.  To be called the A45, this smallest of AMG's will pack a bunch of firsts for the AMG brand.  It will be the first transverse-engine AMG, and the first four-cylinder AMG.  If you're thinking that's a sign they've gone soft, a look into the specs of the engine will force you to think again.

Under the hood of the A45, you will not find a 4.5L anything - it's powered by a 2.0L turbocharged inline-four, called the M133.  Reports on power vary, with some sources saying 330bhp, and Autoblog stating (from an interview with AMG engineers) that it will be more like 370 horsepower and 300lb-ft of torque.  If the latter is true, that puts the M133 in rarefied air as far as specific output goes - 185bhp/l is in the realm of high-strung sports bikes, the old Mazda RX-7 (255bhp out of 1.3L) and the highly modified Evo IX FQ-400.  The A45's two most obvious competitors - the Audi RS3 Quattro and BMW M135i, make 134 (335bhp/2.5L) and 105 (315bhp/3.0L), respectively.

Of course, we know that  bhp/l is about as relevant as A/C bills to Eskimos.  After all, the ZR1 Corvette just barely breaks 100bhp/l, and it doesn't exactly hang around.  330bhp out of 2.0L is a fairly severe 165bhp/l, and the first thought comes to mind there is "turbo lag, and lots of it."  It's a distinct possibility: even with direct injection, and a low-inertia twin scroll turbocharger, there's bound to be a downside somewhere.  More surprising is the relatively low 6,300rpm redline for the M133.  Perhaps it will drive like a MazdaSpeed3 on steroids - tons of boost, and then no more breathing room above 6,000rpm?

Concerns about the A45's driveability might be premature, considering it's had engineering input from AMG's racing engines division.  The engine itself will be assembled alongside other Benz 4-cylinders in the plant at Kölleda (instead of in Affalterbach), but the hand-assembly element remains.

Obviously, channeling 330-370 horsepower through the front wheels of an A-class isn't going to work, which is why the A45 will have active AWD.  An active center differential is a good guess, considering that "sport" mode will channel more power to the rear wheels.  Like all the other AMG's, the A45 will be limited to 155mph, with a "Performance Package" bumping that up to 174mph.  The A45 is rumored to weigh in around 3,300lbs - fairly light for the class, and a good indication it'll be an entertaining steer.

Still, a 185bhp/l 2.0L Turbo with AWD sounds a bit like a Mitsu Evo to me - a world apart from the old AMG design ideas of "stuff a V8 in there.  If it won't fit, hammer away at the engine bay until it will."  It's a sign of the engine downsizing the market - even the high end market - is going through.  Can't wait to see how it drives!

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