The most powerful hot hatch in series production. Well, until Audi once again put the brakes between the RS3’s teeth. Well of course. Ding-dong, turn two, turn one, the A45 is the main bonebreaker of hot hatchback power wars. And now completely new from scratch.
The first A45 appeared in 2013 with 355bhp and more than double AMG’s sales target. More generation variants: GLA Crossover, CLA Sedan, CLA Shooting Brake Estate. The same thing will happen this time: the business is too good not to be. The new one copies the 4WD, 4cyl turbo model, but that’s about it: I ask Ralph Illenberger, head of AMG engine design, if anything stuck, “yeah, two bolts, I think.” I’ll talk more about the engine, but before I get too carried away, here’s what you need to know.
As with the other AMGs, the A45 is now available in two variants, A45 and A45 S. The latter, with an additional 33 hp, more kit as standard, larger wheels (19 instead of 18), larger exhaust pipes large, twice as many diffusers. fins, bigger brakes, variable drive modes and more, it’s the only one to come to the UK. It will cost around £50,000. The CLA saloon goes on sale at the same time, costs around £2,000 more and offers a nearly identical driving experience: the hardware is the same for both cars (except for a minor adjustment to the rear track width), the software was modified to give the CLA a moderately less harsh outlook.
The bodywork has been significantly strengthened with a new under-engine skid plate, a strut-mounted cross member, front and rear lower struts to support the subframes, and front wheel arch inserts connecting the track rails. frame with the A-pillars and stop the deformation under the compression of the suspension. It’s quite an assembly.
While the old car had a relatively rudimentary 4WD system (drive forward until you spot a skid), this one is much more sophisticated. The system takes information from everywhere — yaw sensors, steering angle, throttle, that bottle rolling across the floor — and then distributes it (typically 50/50) between the axles. Up front, a mechanical slip differential distributes power to both sides, but at the rear it’s entirely electronic: a pair of sophisticated clutch packs can send 100 percent to either wheel. Not 4WS, but the effect is similar. Drift mode, available if you max out each setting and put ESP into suspension, carefully limits torque to the front axle as long as you give it maximum lateral attack with steering and throttle.
Now, that engine: It’s hard to call a humble four-cylinder highly specialized, but keep that in mind as I tell you about it. It has been rotated 180 degrees so that the intake is at the front, the exhaust and single turbo at the rear, usefully shortening track lengths and lowering the height of the engine at the front, which allows for a more aerodynamic hood line. Now consider the heat buildup. Forget the hot V8, Illenberger calls it “hot-back” because the exhaust and turbo sit next to each other.
The cooling is amazing. The turbo is cooled by water, oil and air, the latter being channeled through an inlet behind the grille, under the engine cover, then through the exhaust and turbo and through an opening deliberately left in the ground. . The heat shield is considerable. There are three water pumps: electrically driven for the intercooler and cylinder block, plus a more robust mechanical pump for the cylinder head. The latter can pump 280 liters of water per minute, more than double the flow rate of a standard car. The intercooler has to lower the inlet temperature from 200 degrees to 50. When it can’t cope, you can ask the cabin air conditioning system for help.
The engine block is new and is not used anywhere else. It is capable of withstanding combustion pressures of 160 bar, basically as strong as a diesel block. Illenberger admits that he considered twin turbos and turbo-supercharger design before rejecting both for packaging reasons. Apparently AMG boss Tobias Moers’ eyes widened when Illenberger walked in and said he thought he could get 415bhp from a single 2.0-litre turbo with the specs for power, response, emissions etc. correct. The twinscroll blower, which runs on roller bearings, has two separate air supplies from cylinders 1-2 and 3-4. It is pressurized at 2.1 bars.
Speaking of power characteristics, these have fundamentally changed. In the old car, the torque peaked at 2,250 rpm and peaked at 5 km. For a more naturally aspirated feel and to give you a reason to hold each gear, peak torque (369 lb-ft) no longer runs until 5,000 rpm, with delivery revving through the midrange, rather than jumping to the bottom end and then just backtrack.
One other thing: there’s a sound generator in the cabin that relies on a sensor in the exhaust, the gearbox is an eight-speed multi-clutch DCT, it weighs 1550kg, promises a 0-62mph in 3.9 seconds, a 167 mph max, plus 34.0 mpg and 189 g/km CO2. It’s a very different beast to the AMG A35 that appeared last year, using an AMG version of a 2.0-litre Merc unit. The current Class A has specialized in design and technology. Can the full AMG fight off the Audi RS3 and BMW M2 and bring the focus back to the driver?
Our choice of the range.
What’s the verdict?
The last A45 was a great commercial success. Therefore, Mercedes-AMG has done what it does best: invest heavily in R&D of its replacement. The 415 hp engine, the 4WD system, the stiffness of the body, the suspension, the electronics that support everything, everything is very impressive and very well integrated.
It’s a very particular kind of car: an explosive hatchback, big on speed and outgoing mannerisms, lacking a bit of finesse and fit. Leave that for coupes like the BMW M2 or Alpine A110. The A45 has another specification: go fast and have fun. This lines it up precisely with the Audi RS3, a car that is both less talented and less charismatic. The A45 has a pretty big sweet spot: it looks good inside and out, runs quietly when you’re not demanding much, and gets really wild when you are.
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Source : topgear.com