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2021 Mercedes-AMG CLA 45 S v BMW M2 Competition comparison test

By Louis Cordony, 19 Feb 2021 Car Comparisons

2021 Mercedes-AMG CLA 45 S v BMW M2 Competition comparison test

With 310kW, AMG’s new CLA45 S ‘coupe’ packs some serious turbocharged punch – but enough to knock-off one of MOTOR’s favourite cars?

As the Victorian sun melts into the horizon, lighting an impossibly beautiful sunset behind our pair that’s set up for a photo, snapper Ellen says she’s never seen anything like it.

It’s true. But in my mind, I’m thinking the same thing about the Mercedes-AMG CLA45 S parked in front of our BMW M2 Competition. While these compact German rockets differ in many ways – body shape, drive, engine placement, equipment levels and cylinder count – they share a basic purpose: lure new and younger customers into showrooms. And this AMG has gone to mind-boggling lengths to do so.

Three hundred kilowatts is a lot to ask from any engine, but what about just four cylinders? It’s unheard of in production road trim. Bonkers stuff. And yet, that’s what AMG has managed with the all-new M139 plugged into this CLA’s nose. Offering 310kW and 500Nm, it might increase outputs on the old CLA45 by only 30kW and 25Nm, but it’s still a plasma-bore coated, twin-scroll turbocharged marvel. And there’s good reason AMG’s engineers worked so hard on it.

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The last CLA45 spent its life trading blows with Audi’s RS3 sedan, taking some big hits that called for retaliation. Here, AMG wound up a haymaker behind the new A- and CLA-Class, while on a broader level the engine signals a new chapter of thinking. Tobias Moers, AMG’s soon-to-be ex-chief destined for Aston Martin, has said the M139 engine will appear in “not necessarily east-west applications”. If we were betting people, then we’d put a few bob on this four cylinder being closely examined for the next AMG C-Class.

But as one chapter begins, another continues. Over at BMW the M2 Competition replaced its sonorous N55 3.0-litre twin-turbo straight six with the M3/M4’s S55 engine to boost outputs and side-step emissions. It touts an impressive 302kW/550Nm. But given the incoming M3 will debut an even more advanced S58 inline six, this remains the S55’s last stand.

Here, against the CLA, the M2 Competition’s rear-drive pedigree might seem excessive against what is, at face value, a front-wheel drive car over-engineered into an all-wheel drive beast – especially since the M2 has stared down rivals across a broad sweep of price points. The thing is, though, the fundamental hardware behind the CLA45 S, like a ‘Twinster’-style rear LSD and new eight-speed dual clutch transmission, have priced its donor car, the A45 S hatch, at $93,600. Swap in the CLA’s unique wind-cheating shape and suddenly you’re at $111,200 before on-roads. Or a couple grand over the M2 Competition’s $109,900.

We should also mention these two come dangerously close on something other than price. While the CLA engine extracts a huge amount of bang from each litre of capacity – its 155kW-per-litre trumps the M2’s by 55kW, although it also beats a Porsche 911 GT2 RS’s 135kW-per-litre, so the BMW powertrain department shouldn’t feel too disheartened – the fight is fairer on power-to-weight thanks to the CLA’s considerable bulk. The CLA’s shell might use the same 2729mm wheelbase as the A45 S but it straps on a longer tail for a CLS-style silhouette. This increases boot space and overall length, but also helps add 50kg and hoists its total kerb weight to 1600kg. Consider that the M2 weighs 25kg less, and suddenly the CLA’s 194kW-per-tonne only just shades the M2’s 192kW.

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But there’s a remarkable difference in how that plays out at Heathcote Raceway. Not only does the CLA’s all-wheel drive deploy grunt through a variable torque split, but huge 255mm Michelin Pilot Sport 4 S tyres dig in at either end. They’re so grippy that the CLA’s launch control bogs for a moment off the line as it tries to motivate all that Michelin rubber. The M139’s adjusted torque delivery is partly to blame since it’s concentrated its shove above 3000rpm.

After 3000rpm, though, the CLA is so explosive you barely register what happens over the strip’s first half. Since its second, third and fourth gears are closely stacked and its shift mapping in auto doesn’t like venturing past its 6750rpm power peak, the CLA reaches fourth as soon as 115km/h. Lightening quick upshifts deliver 100km/h only 4.09sec after leaving the line. Four hundred metres pass in 12.21sec, setting a time it’ll match over and over with metronomic consistency thanks to a launch control program that awards any idiot.

Such praise is not lost on the M2’s launch system, either, since it handles another 50Nm with half the driven wheels. On the line the system pins revs around 2000rpm, which plays base camp for a 550Nm torque peak that lasts from 2350rpm to 5200rpm. Release the brake and 265mm Michelin Pilot Super Sports only hold for a moment before breaking loose. The ESP’s MDM mode quickly reigns in the first-gear wheelspin, allowing the M2’s ballistic engine to find second gear some traction. Left to its devices the M2 storms to 100km/h from rest in 4.59sec and eventually tags the finish line in 12.57sec. If you’re desperate to emulate its factory 4.2sec 0-100km/h claim then allowing its engine to rev out completely in second might prune a couple tenths, but it needs more road.

Yes, the CLA dominates here. An insatiable appetite for revs, boost and gears drive its slippery nose through the air to overcome greater mechanical drag and snatch a commanding lead. The two car lengths it pulls on the M2 at the 100m mark are almost doubled at the strip’s end. It’s impressive. But on a roll the speed traces reveal that an extra quarter mile or so might crown a different winner. Because while the CLA is travelling 6km/h faster at the 100m mark, that speed difference has shrunk to less than 3km/h once it passes 400m. Remember, the M2 flexes its power peak over a wider band from 5250-7000rpm. It also produces 40Nm more per tonne. So when traction issues finally disappear it slowly closes the gap in speed. But we’ll have to find that out another time.

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Leaving Heathcote Raceway reveals the CLA as the go-to pick for high-speed blasts across country. A relatively long wheelbase only boosts confidence in the all-wheel drive’s road-holding, while a variable-rate steering system that points true around straight ahead nails the CLA towards your intended direction. The M2, meanwhile, can’t spark the same confidence after just hopping in. On paper it is not as short, or wide, as you think it is, but mounting the driver’s seat relatively high closer to the rear axle exaggerates the awkward feeling about its proportions. Its fixed steering ratio helps you judge fine inputs bombing along at speed, but there’s no doubting that its rear footprint, and its huge track width increase over the front’s, creates the suspicion it might bite if you let down your guard.

Reach some corners and you’ll discover BMW engineered on-limit understeer into the M2’s front-end to reduce this possibility. That’s because, again, the rear axle dominates the experience, with how hard you can push the M2 depending on how much torque the rear tyres accept. An active rear differential helps given its computer-controlled locking rate can instantly react to the engine’s twin-turbocharged wave of torque, while retuned dynamics software harmonises the diff and DSC with the power delivery. Together they turn what could be a wicked car into a surprisingly eager corner carver – as long as you respect it. 

Big, sticky tyres help. Pilot Super Sports surround the M2’s powerful brakes with tremendous grip and offer surprising turn-in and traction once they’re warm. Up the commitment, however, and while their limits are high, the tyres transmit little warning about when they’re ready let go. The ESC’s ‘halfway’ MDM mode is quick to react when it does, but a soggy throttle pedal and fuzzy steering feel means suspension squat is your only tactile marker on rear grip. Luckily, the M2’s passive dampers are expertly judged for hard driving – striking a good balance between body control and compliance, even if they’re short on travel.

The CLA, by contrast, is a more accessible device. Fundamentally, grip is outstanding, it steers with laser-like precision and rockets from corners like a Tomahawk missile. But AMG, in hopes of injecting more involvement into the CLA45 S, has bolted an electronically controlled twin-clutch LSD between its rear axles, yet at first it’s hard to notice its effect. Granted, the car’s adaptive damping helps by shifting weight around its footprint. Pin the throttle early and you can feel it squat to push itself along a neutral line.

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Awakening the ‘Twinster’ differential’s playful side, however, requires twirling the powertrain dial on the CLA’s wheel into Race with ESP in Sport (no Drift Mode today). We’re told most of the time only 50 per cent of engine torque goes rearwards so you’ll need big gobs of throttle to overcome the front axle’s tenacity, which quickly feels like you’re forcing it to do something it doesn’t want. Instead, belt at a corner, stab the brakes, throw it in and just when the rear-end lightens, pick up the throttle. Given the differential can direct all its received torque to either wheel, it’ll then tweak your angle a few degrees into oversteer and then shoot you down the road – much like an Audi Sport differential.

Between corners the CLA’s four cylinder is a freak of nature, building shove like an atmo engine twice its capacity. The throttle is so responsive it feels like your right foot is tied to its butterfly valve. All it lacks is an authentic note. AMG banished a cabin exhaust button since regulations have forced it to abandon pops and crackles, but our CLA does not pack a new optional noise amplifier that pumps recorded exhaust noise through the speakers for $680. It’s still convincing in volume, and finds a throaty rort from the active exhaust in Race. But its wail can’t match the M2’s sizzling six for theatre. I’ve dismissed the S55 as bland in the past, but in the M2 Competition with an upgraded exhaust system, it’s orchestral. The gravelly snarl down low transforms into a hard-edged howl that finishes with a gnashing zing.

BMW might not have granted the M2’s seven-speed dual-clutch transmission another life in its all-new M cars, which seems like a loss right now given how rapid it responds. Its long gear ratios also nicely spread out grunt on twisty roads, often placing you in the meat of its mid-range and poised to exploit the S55’s top-end sting for a dab of opposite lock. The CLA’s transverse eight-speed dual clutch, meanwhile, is just as obedient and snappy. The metal AMG paddles are nicer to pluck, too, and easier to find behind the wheel. But for uphill corners the CLA’s second gear, limited to 80km/h, feels too short while the 120km/h third gear is a touch long.

AMG prioritised the CLA and A 45’s ride during development and while it is far from the last word on suppleness, the adaptive damping chassis encourages pushing ahead on roads where the M2 cowers. This extra absorbency also equals superior everyday comfort. Add good low-speed throttle response to that, partly thanks to improved clutch engagement on the new transmission, and it stacks up as easier to use every day. But if you’re regularly darting through traffic then it’s the M2 that offers better outward visibility.

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On looks it can be argued, as it was at MOTOR HQ, the CLA apes a GT63 from some angles. Someone also pointed out its new bum stretches it to the length of a C-Class. The M2, meanwhile, looks more special because it’s obviously so different. Those comically wide guards and the exposed rear muffler canister add a true sense of occasion that invites you to turn around after parking it every time.

When it comes to value, however, the CLA makes a stronger case. It’s a nicer place to sit inside, with a newer cabin that’s littered with high-end technology (but the heads-up display is $790). Radar cruise or even Apple Carplay’s absence reveal the M2 was built to a price. In its defence, and despite their similar asking figure, the M2 is a different proposition. It’s slower off the line but offers a more rewarding drive on account of handling that demands respect but rewards in equal measure. And it has an X-factor lost on the CLA – thanks to its unforgettable sound, cheeky rear-end antics and unique look.

Ultimately, though, it lacks the CLA’s broad spectrum of talent. AMG’s efforts to inject the CLA45 S with ride comfort, low-speed polish and genuine involvement has given it more purpose of being as well as true duality. It’s a mini GT one moment before a click of a dial switches it into an apex predator the next. To extract all this from its four cylinder front-wheel drive origins is astonishing – and j-u-s-t enough to take the win. Because Ellen was right, we’ve never seen anything like it.

MERCEDES-AMG CLA45 S SPECS

Price as-tested: $119,200
Body: 4-door, 5-seat sedan
Drive: all-wheel
Engine: 1991cc inline-4, DOHC, 16v, turbo
Bore/stroke: 83.0 x 92.0mm
Compression: 9.0:1
Power: 310kW @ 6750rpm
Torque: 500Nm @ 5000-5250rpm
Weight: 1600kg
Transmission: 8-speed dual-clutch
kW-per-tonne: 194kW/tonne
Suspension: struts, coil springs, adaptive dampers, anti-roll bar (f); multi-links, coil springs, adaptive dampers, anti-roll bar (r)
L/W/H: 4693/1857/1413mm
Wheelbase: 2729mm
Tracks: 1605/1585mm (f/r)
Steering: electrically assisted rack-and-pinion
Brakes: 360mm ventilated discs, 6-piston calipers (f); 330mm ventilated discs, single-piston calipers (r)
Wheels: 19.0 x 9.0-inch (f/r)
Tyres: 255/35 ZR19 (f/r); Michelin Pilot Sport 4 S

Rating: 4.5/5

Pros: Laser-like precision; incredible grip; rapid acceleration; promising everyday package

Cons: Over shoulder visibility; expensive for a four-cylinder; potential tech overload

MERCEDES-AMG CLA45 S PERFORMANCE

0-10km/h: 0.26 sec
0-20km/h: 0.61 sec
0-30km/h: 1.02 sec
0-40km/h: 1.40 sec
0-50km/h: 1.76 sec
0-60km/h: 2.12 sec
0-70km/h: 2.51 sec
0-80km/h: 2.99 sec
0-90km/h: 3.50 sec
0-100km/h: 4.09 sec
0-110km/h: 4.69 sec
0-120km/h: 5.36 sec
0-130km/h: 6.21 sec
0-140km/h: 7.05 sec
0-150km/h: 7.94 sec
0-160km/h: 8.88 sec
0-170km/h: 10.04 sec
0-180km/h: 11.31 sec

0-400m: 12.21 sec @ 186.24km/h

80-120km/h: 2.42 sec

100-0km/h: 37.83m

SPEED IN GEARS

1st: 56km/h @ 7200rpm
2nd: 80km/h @ 7200rpm
3rd: 122km/h @ 7200rpm
4th: 174km/h @ 7200rpm
5th: 240km/h @ 6350rpm
6th: 270km/h @ 5570rpm
7th: 270km/h @ 4960rpm
8th: 270km/h @ 3925rpm

BMW M2 COMPETITION SPECS

Price as-tested: $114,800
Body: 2-door, 4-seat coupe
Drive: rear-wheel
Engine: 2979cc inline-6, DOHC, 24v, twin-turbo
Bore/stroke: 84.0 x 89.6mm
Compression: 10.2:1
Power: 302kW @ 5250-7000rpm
Torque: 550Nm @ 2350-5200rpm
Weight: 1575kg
Transmission: 7-speed dual-clutch
kW-per-tonne: 192kW/tonne
Suspension: struts, coil springs, dampers, anti-roll bar (f); multi-links, coil springs, dampers, anti-roll bar (r)
L/W/H: 4461/1854/1410mm
Wheelbase: 2693mm
Tracks: 1579/1601mm (f/r)
Steering: electrically assisted rack-and-pinion
Brakes: 380mm ventilated discs, 4-piston calipers (f); 330mm ventilated discs, 2-piston calipers (r)
Wheels: 19.0 x 9.0-inch (f); 19.0 x 10.0-inch (r)
Tyres: 245/35 ZR19 93Y (f); 265/35 ZR19 98Y (r) Michelin Pilot Super Sport

Rating: 4.5/5

Pros: Relentless shove; hair raising exhaust and engine noise; enchanting looks; endearing handling

Cons: No adaptive damping; high seat position; fuzzy steering feel; soggy throttle pedal

BMW M2 COMPETITION PERFORMANCE

0-10km/h: 0.52
0-20km/h: 0.90
0-30km/h: 1.34 sec
0-40km/h: 1.76 sec
0-50km/h: 2.16 sec
0-60km/h: 2.57 sec
0-70km/h: 2.97 sec
0-80km/h: 3.40 sec
0-90km/h: 3.91 sec
0-100km/h: 4.55 sec
0-110km/h: 5.14 sec
0-120km/h: 5.79 sec
0-130km/h: 6.54 sec
0-140km/h: 7.39 sec
0-150km/h: 8.40 sec
0-160km/h: 9.39 sec
0-170km/h: 10.54 sec
0-180km/h: 11.82 sec

0-400m: 12.57 sec @ 186.15km/h

80-120km/h: 2.35 sec

100-0km/h: 37.21m

SPEED IN GEARS

1st: 57km/h @ 7500rpm
2nd: 105km/h @ 7500rpm
3rd: 160km/h @ 7500rpm
4th: 214km/h @ 7500rpm
5th: 250km/h @ 6875rpm
6th: 250km/h @ 6500rpm
7th: 250km/h @ 5170rpm