BMW M135i v Mercedes A45 AMG-7

BMW M135i v Mercedes-Benz A45 AMG: Comparison Review

Hatches don’t come any hotter than the BMW M135i and the Mercedes-Benz A45 AMG. Nor do rivalries come any fiercer.

BMW has been building fast hatchbacks since the 130i of a decade ago, and its M division is esteemed in building compact six-cylinder performance models seemingly since the dawn of time.

Mercedes-Benz AMG, however, has after several decades of trying and through a number of model-cycle revisions, only just made its current C63 a worthy rival to the M3.

Yet the plucky performance division from Affalterbach has already turned its attention to making its first production hot-hatch, utilising its first four-cylinder engine, and one that not only eclipses a six-cylinder BMW for outputs, but is the world’s most powerful production four-cylinder.

It also boasts a specific output of 133kW per litre of capacity that is unbeaten by any production car, regardless of engine size or price.

The A45 AMG doesn’t so much stroll into territory owned by BMW, then, but struts in with swagger and plenty of big-talking.

In some ways the BMW M135i has little to prove but everything to lose.

Despite not being a fully-fledged M model like the departed 1 Series M Coupe was, this one-tier-lower M Performance model is not only brilliant, but inarguably the best model in the manufacturer’s current range now that the M3 is departing.

Among a patchy current range that has largely been lagging against equivalent Mercedes-Benz models, BMW Group Australia knows the M135i is its greatest return-serve. Quietly, to us, Mercedes-Benz Australia executives ackowledge that, too, but they also think the cocky A45 AMG can beat it.

Both local posts desperately wanted this comparison to happen, so much so that Mercedes-Benz made the sold-out A45 available for us for a day in Melbourne, and BMW trucked a demonstrator M135i from Sydney down to do battle – a logistical nightmare, but a 6am till 8pm drive and photo shoot was on.

(As an aside, we couldn’t wait till December for the Audi S3 to launch, and at $59,900, the bigger question may be be whether it’s worth the extra over a Golf GTI Performance Pack…)

A combative competitive spirit can also be seen in among the most aggressive pricing and specification seen in a comparison test.

Since we last tested the BMW M135i (in April 2013) the price of the eight-speed automatic model tested here has fallen by $7500 to $64,900, which also makes the car $10,000 cheaper than the Mercedes-Benz A45 AMG.

That, however, is not the end of the story.

Option the M135i with the equipment standard in the A45 AMG – including reversing camera with auto-parking assistant ($1170), Harman/Kardon audio with digital radio ($1100), electrically adjustable front seats ($2730), sunroof ($2600), and lane departure warning/collision detection and warning ($1400) – and the price is just $1000 less than the A45 AMG.

The BMW still misses collision auto-braking and heated front seats, though, and gets 18-inch alloy wheels to the Benz’s 19s. Our test M135i was also further optioned with adaptive M suspension, which for $1420 made the car just $420 more expensive than our unoptioned A45 AMG.

It would be difficult to find a more evenly matched showdown.

There are, however, many mechanical differences between the two rivals. In addition to the BMW being a six-cylinder and the Mercedes-Benz a four-cylinder, the M135i sends drive through an eight-speed torque converter automatic to the rear wheels only, where the A45 AMG utilises a seven-speed dual-clutch automatic and all-wheel drive.

Despite their differences, the 2.0-litre AMG engine and 3.0-litre BMW engine each with a twin-scroll single turbocharger and produce an identical 450Nm of torque.

But where the M135i produces its maximum pulling power between 1250rpm and 5000rpm, the A45 AMG makes just 250Nm at 1500rpm before rising to its full output between 2250-5000rpm.

The A45 AMG also makes 265kW of power at 6000rpm, compared with 235kW at 5800rpm in the M135i, but runs into its rev limiter at 6600rpm where the BMW will extend all the way to 7200rpm.

Partly thanks to standard launch control and all-wheel drive, the A45 AMG claims a 4.6-second 0-100km/h. Despite the M135i weighing 1445kg, or a full 110kg less than its rival, it scrabbles for traction off the line and claims a half-second-slower time to triple-figure speed.

Slide into the AMG’s slickly finished cabin – with lovely woven carbonfibre-look trim on the dashboard, stubby Affalterbach-embossed gearlever, silver and red highlights, superb Recaro sports seats, and Alcantara-trimmed steering wheel with chilly-to-touch magnesium paddle shifters behind it – and it immediately feels premium beyond its price tag.

Further back, the A45 AMG also has more rear legroom than the M135i, particularly for the centre rear passenger thanks to a less intrusive tunnel, although the 341-litre boot is 19L shy of its rival’s.

The engine starts with a throaty bark, and the sports exhaust – optional overseas, standard here – pops distantly as an accompaniment. Start to drive the A45 AMG and the exhaust dominates the aural experience. The four-cylinder simply doesn’t sound inspiring, its slightly grainy and thrashy soundtrack drowned out by an exhaust blurt on every upshift, or pop and crackle after every throttle lift.

In Comfort mode, the automatic gearbox is slow to respond to the dull throttle, which doesn’t help when there’s some lag down low – remember the 250Nm at 1500rpm. Switch to Sport and the car comes alive, holding gears more prudently, but still not downshifting aggressively enough under brakes.

The manual mode is required during hard driving, but there’s a sizeable gap between second and third gear – the latter ratio is 1.05:1! – which along with the low-ish rev ceiling can be frustrating. The gearbox also reacts too slowly to the slap of the left paddle.

No such problems with the BMW eight-speeder. Although the interior of the M135i looks relatively bland, with anorexic-looking front seats, dark colours, and cheap plastics, the engine and transmission feel more special than those in the Benz.

Particularly off the line or when above 5000rpm, the A45 AMG is untouchable. But despite the lower power output, the lighter M135i feels just as fast when the throttle is flattened from any speed. The automatic slurs into tall gears like the AMG’s does, but the throttle is much sharper, and the gearbox is much quicker to respond.

Although dual-clutch gearboxes are typically quicker to shift than torque converter automatics, the ZF-sourced BMW auto is faster and has a better spread of ratios that team perfectly with both the extra torque down low and extra revs up top.

The creamy, raunchy six-cylinder soundtrack beats the four-cylinder AMG’s hands down, too, even if the exhaust isn’t as shouty. The engine dominates the BMW experience in the same way as the exhaust always dominates in the AMG, and we know which we’d prefer…

The A45 AMG may feel more premium inside, but the M135i feels more premium in terms of its ride and refinement.

The Benz has a very hard suspension tune that, in isolation, is acceptable for a focused hot-hatch, but the constant jiggling segues into abruptness over sharp-edged road imperfections. On really rough roads, bump-steer can throw the car off line.

We’ve previously tested the BMW with the standard M Sport suspension, which proved mostly excellent but also a bit soft on really rough roads.

With the optional adaptive dampers fitted to our test car comes three different suspension settings – Comfort, Normal and Sport. All three are excellent, but Sport’s ability to just hold the car’s body tighter to the road surface without compromising comfort is a masterstroke.

From point to point between corners, the A45 AMG is undoubtedly quicker than the M135i. It sits flatter and has astonishing thrust out of bends thanks to its all-wheel-drive system, which always sends drive to the front wheels but can briefly push 60 per cent of drive to the rear.

Unlike in the Volkswagen Golf R – which like the Benz is Haldex-branded – the system actually works, so punching the throttle early in really tight bends can result in slight oversteer.

Yet take some speed into the same bend and the A45 AMG will, in typical all-wheel-drive fashion, push into understeer, and understeer earlier than the M135i will.

Take the bend again and hold the brake deep into the corner to keep the nose pointing towards the apex, and the rear will start to unhinge and make the car feel edgy. It’s the same if the throttle is held into the corner then lifted (see the below pic where it’s cocking a wheel…).

Depending on the conditions and driver input, the A45 AMG presents a variety of different attitudes. The Mercedes-Benz may run the full gamut from feeling blunt to feeling edgy, but it’s sometimes difficult to find its sweet spot.

No such difficulty with the M135i.

This is a hot-hatch that speaks fluently to its driver in all conditions, seamlessly blending a sharper, lighter front end – there’s a heavier six-cylinder up there, but no driveshaft – with sublime rear-wheel-drive response. The BMW rolls more than the Mercedes-Benz, which can initially be disconcerting, but it actually helps the driver better feel the exquisite balance.

On smooth roads the A45 AMG may be quicker point to point, but the M135i pounds over imperfect surfaces – in other words, Australian backroads – far more comfortably and confidently.

The BMW, with its quicker transmission, greater low-down torque and closer ratio set, also allows the driver to be faster and more fluent more of the time than in the Mercedes-Benz, even if the A45 AMG has the potential to be faster when everything gels.

Standard variable-ratio electro-mechanical steering in the M135i is also superior. It’s rare these days for a BMW steering system to trounce a Benz equivalent, but in this case it offers fewer turns lock-to-lock (2.2 turns versus 2.7) and more incisive on-centre feel.

The A45 steering isn’t quite as feelsome as that in other AMGs, with a slight vagueness when trying to pin a fixed line through a corner, but it is otherwise excellent in isolation.

The single blot on the BMW’s scorecard is its electronic stability control (ESC) calibration. Curiously, an electronic differential lock – which brakes a spinning inside wheel during hard cornering – only enables when ESC is completely switched off.

It works brilliantly, and although power-oversteer manouevres are harder than they would be if it had a proper mechanical limited-slip differential, it allows plenty of bum-wiggle while acting like a subtle ESC.

In many ways it should be labelled ESC Sport, as it is in the A45 AMG. The Benz system is less intrusive than the BMW’s when left on, but then it can rely on extra all-wheel-drive traction that keeps the body straight.

Despite its heritage, the BMW M135i was always the underdog in this contest.

It isn’t a ‘proper’ M-car, to many eyes looks a bit awkward – though we love the proportions – and doesn’t shout from loud exhausts and sparkly trimmings about world-firsts and straight-line speed like the A45 AMG can.

But even placing aside the subjective preferences between straight-line speed and point-to-point pace (A45), and touchy-feely chassis intimacy (M135i), in core assessment terms the BMW has a better transmission, superior steering and a far more soothing ride.

The Mercedes-Benz hits back with a nicer interior and better stability control, but on our watch that’s only two against three...

The Mercedes-Benz A45 AMG is an excellent first-time attempt at building a mega hot-hatch, but particularly with recent price cuts, the BMW M135i is more impressive than ever and remains the one to beat.

This comparison review first appeared in the October/November issue of the CarAdvice iPad magazine app. Head to the Apple App Store to download the entire issue.

Photography by Cristian Brunelli.

BMW M135i

Price: $64,900
Engine: 3.0-litre 6-cyl turbo petrol
Power: 235kW at 5800rpm
Torque: 450Nm at 1250-5000rpm
Transmission: 8-speed automatic
0-100km/h: 4.9 seconds
Fuel consumption: 7.5L/100km claimed
CO2 emissions: n/a

Mercedes-Benz A45 AMG

Price: $74,900
Engine: 2.0-litre 4-cyl turbo petrol
Power: 265kW at 6000rpm
Torque: 450Nm at 2250-5000rpm
Transmission: 7-speed dual-clutch automatic
0-100km/h: 4.6 seconds
Fuel consumption: 6.9L/100km claimed
CO2 emissions: 161g/km

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