New compact king of the Nordschleife

The drift angle in the first Nordschleife bend is almost like a Moselle hairpin bend, in the Hatzenbach there is wild dust as the car cuts over the curbs, and actually the only thing missing are the vineyards off the Eifel asphalt – the Mercedes-AMG A 45 S 4Matic+ almost turns the Nordschleife into a special stage thanks to its highly dynamic all-wheel-drive technology and conjures up a bit of Rally Germany flair in the cockpit.

While the A 45 S is already lunging with a sharp two-liter growl out of the right-left corner combination of the Hocheichen section toward Quiddelbacher Höhe and the airfield, we briefly turn our attention to the standout technology highlight of the muscle A-Class.

Dynamic wonder all-wheel drive
Hans-Dieter Seufert

Depending on the driving situation and the driving program, propulsion is distributed separately to both rear wheels. Control of the drive torques to the front and rear axles and between the two rear wheels is electromechanical.

The team from Affalterbach calls the variable all-wheel drive system “AMG Performance 4Matic+ with AMG Torque Control” with two electronically controlled multi-plate clutches, which are hidden in the rear axle transmission and are each connected to a drive shaft on the rear axle. This means that the drive power can not only be continuously and variably distributed between the front and rear wheels, but also between the left and right rear wheels.

Depending on the driving situation and the driving program, the drive is distributed separately to both rear wheels. The drive torques to the front and rear axles and between the two rear wheels are controlled electromechanically.

Six driving programs are available: Smooth, Comfort, Sport, Sport+, Individual and Race. The A 45 S will never become a sedan, but the drive programs offer an astonishing spread and influence parameters such as the accelerator pedal characteristic curve, shift times and shift points, the characteristic curve of the optional adaptive dampers, the steering characteristic curve and the setting of the exhaust gas flap system. It’s logical which setting is chosen for the Nordschleife visit: Race and ESP off! Attack!

253, 254, 255 km/h – the power of the hot A-Class becomes apparent at the latest when the compact sports car approaches the Schwedenkreuz section. Clock comparison: Here the A 45 of the predecessor series W 176 had “only” 243 km/h on its Nordschleife lap. With a rated output of 421 hp, AMG gives the inline four-cylinder turbo 40 hp more than its direct predecessor. And only finicky advocates of naturally aspirated engines harp on the fact that a gentle torque dip can be felt in the lower rev range. The maximum torque of 500 Newton meters (previously 475 Nm) is available at 5,000 rpm – the high-revving design almost has a bit of naturally aspirated engine character.

Most powerful production four-cylinder

Mercedes-AMG A 45 S 4Matic+, Motor

Compared with the predecessor model, the engine has been rotated 180 degrees around the vertical axis. Added to this is a new twin-scroll turbocharger with 2.1 bar maximum boost pressure.

It is not only the power and torque that have increased. To optimize air flow by means of shorter paths and fewer deflections, the engine has been rotated 180 degrees around the vertical axis compared with the predecessor model. New twin-scroll turbocharger, compressor and turbine wheel shafts mounted in anti-friction bearings for the first time, 2.1 bar maximum boost pressure – theoretically, one could now philosophize for much longer about what AMG calls “the most powerful four-cylinder turbocharged engine produced for a large series,” but in practice the Aremberg curve is already approaching.

Braking, fifth, fourth, third gear. Unlike in the A-45 predecessor, there are not seven gears available, but an eight-speed dual-clutch shifts gears – and especially in the race program, this is extremely snappy. Recommendation: It’s better to shift up and down the gears yourself in manual transmission mode, since the transmission takes a bit too long to downshift when braking dynamically in automatic mode. Here, too, the perfect time for upshifting is visualized by the digital instrument cluster, which can be set in three instrument looks (Classic, Sport, Supersport). In the Supersport instrument look, the shift lamps flash red at the lower edge of the tachometer.

Neutral handling

Turn in, get on the gas early, and then let the all-wheel-drive system do the work. How does that feel? Similar to a rear-wheel drive car, the rear of the compact high-flyer presses lightly under load over a wide curve. In this way, the A 45 S transforms understeer into neutral handling. Without exaggeration: If you “turn on” the fast A-Class at the entrance to the bend via a snappy steering impulse, you can easily drift through numerous bends on the Nordschleife with this highly dynamic all-wheel drive system.

To be honest, you actually have to pull yourself together quite a bit not to drive too much and too sideways with the A 45 S. At Hockenheim, for example, the dip and the south curve tempt you to combine both curves in a long drift. The fact that this dynamic all-wheel-drive system is not just for show, but that the mixture of slightly pushing rear end and propulsion is ideal for fast lap times, is not only evident now on the Nordschleife, but also impressively on the GP circuit at Hockenheim.

Here, the compact sports car chiseled a lap time of 1:55.7 minutes into the asphalt – a lap time, a demonstration of power and a challenge at the same time. This suddenly puts the compact from Affalterbach in the league of the Porsche 718 Cayman GT4 (lap time individual test sport auto 11/2019: 1.55,0 min) and BMW M2 CS (lap time individual test sport auto 10/2019: 1.55,8 min).

Uncompromising tire choice

Mercedes-AMG A 45 S 4Matic+, Rad

Of course, the current choice of tires also plays a major role in the increased lateral dynamics. Instead of the standard Michelin Pilot Sport 4S tire, the A 45 S now wears the optionally available Pirelli P Zero Trofeo R.

It’s not just the comparison with the supposedly stronger competitors that shows that the A 45 S put in a great lap at Hockenheim in the super test. The muscle A-Class is a full five seconds faster than in the individual test in sport auto 10/2019. Of course, the current tire choice also plays a major role in the increased lateral dynamics. Instead of the standard Michelin Pilot Sport 4S tire, the A 45 S now wears the optionally available Pirelli P Zero Trofeo R.

We don’t need to go into detail about the Trofeo R’s suitability for everyday use at this point. As expected, the Italian semi-slick, which is optimized for dry grip, needs a considerable amount of working temperature even with the special Mercedes-AMG specification (MO1), as the moderate cold braking value shows. Once up to temperature, these hardcore slicks shine and perfect the hot A-Class.

Whereas in the individual test with the Michelin standard tire the moderate deceleration (100-0 km/h warm: 35.8 meters) had to be criticized, the A 45 S now claws its way into the asphalt and puts down a sports car-like braking value (100-0 km/h warm: 32.9 m). The braking system also works steadily in the standard braking test and during the fast racetrack laps.

However, not only the high grip level of the Trofeo R is responsible for the exceptionally fast lap time at Hockenheim, but also the very good boundary conditions with cool outside temperatures on the test day. And: You have to adapt the way the all-wheel-drive technology works to your driving style. If you want too much at the entrance to the bend, you push the A 45 S into dull understeer – miracle all-wheel drive or not.

Weight? Yellow-red card!

Mercedes-AMG A 45 S 4Matic+, Leistungsmessung

If it weren’t for the weight! Just imagine the lateral dynamic regions the A 45 S would be in if it were 200 kilos lighter. 1,625 kilograms is simply too much. Period!

After all, there’s one thing that even clever technology can’t hide from a certain point: the front-heavy weight distribution and the high total weight. 61.7 percent of the total 1,625 kilograms are on the front axle. For the weight increase of 51 kilograms compared to the predecessor, there is the yellow-red technology card – sorry, AMG, we are still talking about a compact model here.

The trick to eliciting fast lap times from the A 45 S despite its fat pads? Don’t brake late into the corner, but decelerate early at the entrance to the corner and step on the gas pedal all the sooner for it. If you take this to heart, the compact hero from Affalterbach will first impress you with its precise turn-in behavior at the entrance to the bend and then with a dynamic fireworks display that you wouldn’t have thought possible. Under load, the all-wheel drive vehicle then throws itself into the further course of the bend with a wonderful mix of brute traction and a slightly oversteering rear end.

Progressively depress the accelerator pedal from the apex? No, the hardcore A-Class almost greedily demands a different driving technique – turn in and then slam the accelerator pedal down on the floor assembly as quickly as possible. The rest is taken care of by the great all-wheel drive technology.

Back to the Nordschleife: Particularly in slower cornering passages with tighter curve radii, such as in sections à la Aremberg, Kallenhard, Wehrseifen or Steilstrecke, where compact sports cars with front-wheel or all-wheel drive naturally always like to push into understeer, the AMG compact sports car scores with very neutral handling, or it even surprises with slight power oversteer.

Ideal set-up for the Ring

Mercedes-AMG A 45 S 4Matic+, Lenkrad

The optional adaptive suspension called AMG Ride Control offers three damper settings: Comfort, Sport, Sport+.

It is not only the new all-wheel drive technology that deserves high praise from a driving dynamics perspective. Especially the tuning of the newly developed AMG suspension at the limits immediately shows that the driving dynamics developers from Affalterbach spent a lot of development time on the Nordschleife.

The set-up of the optional adaptive suspension called AMG Ride Control with three-stage damper adjustment (modes: Comfort, Sport, Sport+) springs tightly in the sportiest mode, but not as hard as its predecessor. The tendency to roll at the limit on the Nordschleife remains low. The A 45 S casually slurps away bumps and crests. The A 45 S is also extremely sure-footed on fast curbs, such as the Fuchsröhre or the Wippermann section.

The compact sports car impresses with an astonishingly high level of mechanical grip, and not just because of its choice of tires today. The sensitive and precise, but not too sharp, electromechanical steering with speed-dependent servo assistance, variable steering ratio (14.4:1 in the center position) and two characteristic curves fits into the overall driving dynamics concept.

And then you fly over the crest of Pflanzgarten 2 into the Stefan-Bellof-S section, already uncorking the champagne in your mind to celebrate the A 45 S a little later at the finish line at T13 for its outstanding lateral dynamics performance. And then this: Suddenly, at a speed of around 190 km/h, fifth gear jumps out, the A 45 S changes to “neutral” with a warning message on the instrument cluster and rolls along with no propulsion.

New compact king

Mercedes-AMG A 45 S 4Matic+, Exterieur

Despite or thanks to everything: With 7.49 minutes, the Mercedes-AMG A 45 S is the new compact king in the super test – and with a large gap to the competition. Congratulations, Mercedes-AMG!

Most likely, this action is a kind of component protection of the all-wheel drive system, which intervenes when special parameters fear a technical knockout of the system. This problem also occurred on the few warm-up test laps beforehand – and exclusively at this point on the Nordschleife, when the wheels on the front and rear axles are unloaded or loaded under full load at short intervals. Especially on the Pflanzgarten-2 crest and on the bumps of the right-left-right alternating passage of the Stefan-Bellof-S, highly different forces act on each individual wheel.

In this situation, you really appreciate the steering column gear selector lever, which is one of the few details that doesn’t really fit in with the sporty character of the compact car. Pull the lever three times and fifth gear is back in, and the Nordschleife chase continues at full throttle. However, it feels like the action took two minutes. In your mind, you almost bite the yellow 12 o’clock mark out of the upper steering wheel, which, like the entire interior, impresses with its high-quality materials and very good workmanship.

In reality, the technical faux pas only gives away eight tenths of a second – 7.48 minutes turns into a lap time of 7.49 minutes. So the great Nordschleife performance and its new title only detracts from the action to a very limited extent: the Mercedes-AMG A 45 S is the new compact king in the super test – and by a wide margin over the competition. Congratulations, Mercedes-AMG!

Survey

… simply lunacy! Totally inappropriate.

… simply awesome! And hopefully not yet the end of the line.

Nürburgring Nordschleife
7.48,80 min

With a lap time of 7.49 minutes, the A 45 S is 15 seconds faster than its direct W-176 predecessor with 381 hp. Not only the increase in rated power is responsible for the significantly improved lap time, but also the much more dynamic handling. Much of the agility gain is due to the new all-wheel drive system. On the Nordschleife, the A 45 S moves largely neutrally. In tight corners it even pushes very slightly with the rear under load. The optional semi-slicks significantly improve the grip level. And the braking system? Remains consistently stable at the Ring!

Hockenheim-Ring Small circuit

With a lap time of 1m 55.7s, the Mercedes-AMG A 45 S is the fastest compact sports car on the GP circuit. As on the Nordschleife, it shines at Hockenheim with neutral handling, thanks above all to the new all-wheel-drive system. But physics eventually reaches its limit with a high vehicle weight of 1,625 kilograms. It’s important not to set the braking points too late and to start braking a little earlier so that the variable all-wheel drive can show its dynamic prowess. If you overdo it at the entrance to the bend and push too hard, the A 45 S will quickly rush into dull understeer.

Acceleration / braking
19.5 sec

Thanks to its increased performance, the A 45 S sets itself apart from its predecessor in this discipline. The Launch Control works reliably and smoothly. However, at 4.7 seconds (129.2 m, 11.9 m/s²), the predecessor was slightly better at 200-0-km/h deceleration.

Acceleration 0-200 km/h:
14,7 s
Braking 200-0 km/h:
4,8 s

Wind tunnel

The optional aero package (modified front splitter, additional flics on the front apron, rear wing) improves the aerobalance. In contrast to the predecessor model, the current A 45 S thus has slight downforce on the rear axle at 200 km/h for the first time.

Front axle at 200 km/h:
9 kg lift
Rear axle at 200 km/h:
5 kg lift

Lateral acceleration
1,30 g

Compared with the A 45 predecessor model of the W 176 series, the maximum lateral acceleration values of the current model are somewhat lower. Not surprisingly, under load the rear end of the current A 45 S pushes quite slightly with slight power oversteer. Even though the minimal stall on the rear axle promotes agility, lateral acceleration drops as a result.

36-meter slalom
137 km/h

The little AMG copes better with the wide radii of the fast 36-meter slalom than with the twisting 18-meter slalom. The all-wheel-drive car counters load changes with lateral stiffness. It’s advisable to keep the throttle on at all times and steer in a bit earlier, so the rear wheels stay on track even during the rapid succession of direction changes.

Swerve test
149 km/h

The body tilts visibly and noticeably during the short, hard turnovers in the swerve test. The A 45 S seems a bit sluggish here, it wants to be steered in earlier and reacts clearly to load changes. The suspension tuning is a bit too soft for the special driving dynamics disciplines, so the potential of the semi-slicks cannot be fully exploited.

Conclusion

It’s astonishing to see the driving dynamics spheres the A 45 S can reach. Apart from the gain in agility and the fast lap times, the new all-wheel drive technology also offers great driving fun potential. I’ve rarely driven an all-wheel-drive vehicle as sideways as I do with the A 45 S. Just as crazy: the outrageously high test car price of almost 80,000 euros.

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