Mercedes-Benz A45 AMG 2012 Review - International

Riding in cars is not motoring.com.au’s thing; not when what we’d rather be doing is driving them.

Too many still-secretive models get a sneaky leg up in the press with semi-serious evaluations because they get ridden in long before they’re driven. And, normally, it’s not our go.

Still, we can compromise when it’s appropriate and, for AMG’s first four-cylinder car, we think it’s appropriate.

The A45 AMG rings in a whole world of firsts for Benz’s AMG powerhouse, including its first ever four-cylinder production engine, its first all-wheel drive passenger car in yonks, its first front-wheel drive-based car and its first dual-clutch gearbox.

What’s more, this car won’t make its official debut before the 2013 Geneva motor show next March, before arriving in showrooms somewhere around the middle of next year.

But AMG, the maker of a whole range of things bent on destroying their own rear tyres with V8 and V12 engines, knows it can’t let its foes continue to have this fast hatch caper all to themselves.

That’s why it’s building a 280km/h missile to turn the A-Class from a once-conservative choice for older folk into something younger people may not automatically laugh at.

At least, that’s what AMG development boss Tobias Moers is telling me as he flicks the Sport button on to sharpen up the throttle response, slash the gearshifting times and open up the exhaust to make big-boy noises as he heads out on the Hockenheim circuit.

Mr Moers, one of the better drivers amongst car industry executives, has already taken us on a 50km loop in the surrounding countryside and was now determined to attack the track to show the little A-Class AMG was, indeed, a real AMG.

You could be forgiven for thinking it might not be. After all, it runs a Haldex all-wheel drive system, and that’s never ideal for hard-core drivers. It’s also based on the A-Class, which has historically been aimed at retirees far more than hot-hatch tyros.

And yet, here it is, bucking and sliding through mid-corner wet patches, tucking its nose back in or letting its tail walk wide whenever Mr Moers asks it to by tweaking his brake or throttle angles.

And it goes. Hard. Mr Moers insists the little A45 AMG will punch to 100km/h in around the “4.6 to 4.8-second range”, though the exact details aren’t confirmed yet.

There is “at least” 450Nm of torque on hand from 2000rpm and Mr Moers insists the car will have “around 350 horsepower” or 260kW when it launches early next year.

The rivals are obvious – BMW and Audi. While Audi’s five-cylinder not-for-Oz RS3 was a key benchmark (and one that Moers claims is six seconds a lap slower around the Nordschleife than his baby), the other was BMW’s 1 Series M Coupe.

“The big market here in Germany is under 50,000 euros, including tax - that’s what the target is for the A45 AMG,” Mr Moers said.

It’s a no-brainer that AMG has turbocharged the living daylights out of it, with a single big, twin-scroll turbo cramming up to 2.8 bar of pressure into the motor and still belting out huge blobs of low-end torque.

Then there’s the noise. Cruising around the country roads in its Normal mode, the A45 AMG sounds a little flat, but kinda deep. It’s a different story when the whip gets cracked in Sport mode, with a savagely crackling, popping braaaap on every up shift, a lingering depth to every rpm and an outrageous blip on the throttle on each down shift.

Then there’s the ride quality, which feels too hard on some of the cobbled German village streets, but sits nicely flat on Hockenheim’s wide open curves. The reason, Mr Moers explained, is that it eschews variable damping rates in favour of a fixed-rate spring and damper set-up. And he admits the mix isn’t quite right yet.

From the passenger seat, though, it doesn’t feel far off. Certainly, the pops and crackles on each gearshift will need to be toned down for the road, even if they’re cool for the track. The dual-clutch gearbox is terrifically quick and the handling balance looks – with a big rider here – better than the layout suggests.

But it’s the engine that always counts most at AMG, and instead of taking Benz’s 1.8-litre in-line four-cylinder, they’ve gone their own way. Sort of.

The external dimensions of the new direct-injection engine are identical to the mainstream Benz stuff, as are its bore spacing and its bore and stroke dimensions. There is no variable valve lift but the A45 borrows Benz’s variable timing on both the inlet and exhaust cams, but that’s about where the similarities end.

Where the block for the Benz 1.8-litre motor is die-cast, the AMG version is sand-cast, like most pure performance motors, and so is the crankcase.

“We can use different materials in sand-casting versus die-casting,” Mr Moers explained. “We use the same dimensions as the A-Class engines because it means you can use the same parts outside the engine and bolt into the same bolt holes as the A-Class.”

Or, as AMG’s senior powertrain engineering manager Dr Jörg Gindele explained, it’s basically a brand-new engine that fits into the holes of a less interesting engine.

“It’s nearly brand-new, this engine. There are some parts we try to share with the base engine but it’s not many,” he said.

“We nearly made a completely new development for this, but not just this but the gearbox and the drive system, too. To have such a high power output, we need to change almost every part.”

That program began with the decision to sand-cast the crankcase, which scored particular attention because of the added stiffness it needed to handle the added combustion pressures.

“The peak pressure in combustion we increased from 90 to 140 bar. That’s a lot and we need a very stiff structure,” Dr Gindele said. “New pistons came next, then new camshafts, new cylinder-heads, new connecting rods, new crankshaft…

“The block is new and the head is new. We keep the bore spacing but the structure is new because with sand-casting we can make the structures more compatible for higher engine loads. We have a better stiffness in the structure.”

Even the water pump is new, because with the A45 AMG’s extra urge comes the need for about 20 per cent more cooling volume and the standard item simply couldn’t generate it.

But just because its main headline act is high torque and high power from a turbocharged engine, don’t believe the A45’s engine won’t rev.

“We are revving to 6700rpm for the limiter on this car,” Dr Gindele explained. “But we get the power peak at 6500rpm.

“We have taken this one repeatedly out to 7200rpm in testing and maximum torque is there between 2000rpm and 4800rpm. We tried it and it was working but we don’t see any need to rev higher than this 6700 in production.”

Unlike the standard V8 twin-turbo motor, the A45’s little 1.8 won’t be offered with a repowered Performance Pack – and not just because Volkswagen has pinched the traditional AMG packaging name for the Golf, either.

Nor will the engine be just a grunter, because Dr Gindele predicts fuel economy that may dip into the high sixes on the combined city/highway cycle in litres/100km. That will mean a highway cycle in the mid-to-high fours.

Alongside all that engine sits a dual-clutch seven-speed gearbox that feels as smooth as it does fast – except when AMG deliberately interrupts its work to make some more noise.

It sits with the lead-in parts of the Haldex all-wheel drive system, designed to run as a front-wheel drive most of the time, but with all-wheel drive on offer when it’s needed.

“The car can send 50 percent of the drive to the back diff if it needs to and you vary the the torque split with the ESP button. It’s normally front-wheel drive with the AWD as a traction support system, but in Sport it moves more torque to the back,” Mr Moers said.

While the core of the dual-clutch ‘box is the same as it is in the A250 Benz, it has been heavily reinforced internally and has had its cooling rates bumped up, too.

“We changed a lot of gears.” Dr Gindele admitted. “Most of them, we just choose a better material for them instead of changing them.

“If you look at what we’ve done, we have we made better materials and make the individual gears a bit thicker and reinforced the the clutches.”

While the powertrain represents the biggest upgrade from the A-Class, it’s not the only upgrade. Almost the entire suspension has been ripped out and replaced, with a couple of exceptions that AMG forced through onto the main layout when the A-Class was under development.

For example, the steering knuckle is the same one that Benz asked AMG to develop for the A250, but with a few more tweaks, and the rear subframe and all-wheel drive clutches are the same, too.

“These are over-engineered for the A-Class, at our insistence, because that’s what we needed in this car and it’s better this way around” Mr Moers admitted.

So that will be the same, but the rest of the suspension is completely different - different kinematics, different steering, different layout, different springs and dampers and different bushes.

And, if the A45 AMG is a bit too hard, the upcoming CLA sedan will use essentially the same AMG-developed hardware and software, but will ride a bit softer than its hatchback stablemate.

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