Mercedes A45 AMG vs Audi S3 vs BMW M135i: CAR Giant Test (2013) | CAR Magazine

Mercedes A45 AMG vs Audi S3 vs BMW M135i: CAR Giant Test (2013)

Published: 08 August 2013 Updated: 18 August 2015

Photography by James Lipman

Within months of each other, the big three premium German carmakers have released their own £30k-plus hot hatch. All boast turbocharged engines and 300bhp, but which is best: Mercedes A45 AMG, Audi S3, or BMW M135i? Read on for the definitive CAR verdict.

A new breed of fast family car

We used to be driving ourselves dizzy up here in trick Mitsubishi Lancer Evos and Subaru Imprezas on steroids, relatively affordable fast cars that loomed large inside our heads and on our bedroom walls. Ten years on, however, the once untouchable four-door Japanese batmobiles are about as en vogue as a Nokia 3110 mobile phone or Rio MP3 player. Instead, the compact crackerjacks most petrolheads embrace in 2013 still can be had with four doors, four-wheel drive and turbocharged four-cylinder engines, but they are no longer street-legal derivatives of rally-bred icons made in the Far East. It’s Deutschland über Alles these days, premium eclipsing mainstream, Freude durch Kraft dressed up in more socially acceptable formats. Offering a similar mix of exciting dynamics, engineering excellence and fire-breathing performance, the latest masters of the super-GTI segment are the 296bhp Audi S3, the 316bhp BMW M135i, and the new (and utterly rampant) 355bhp Mercedes A45 AMG. Gentlemen, start your engines for a two-day, no-holds-barred shootout on the Dolomites’ finest tyre-shredding, brake-eating turf.

Normally in June, all passes connecting Italy to Austria and Switzerland are open, but since this spring is an autumn which has been pulled forward, evidently erasing summer in the process, we had virtually the entire Alps to ourselves. Wherever a sign read ‘Road closed due to snow’ there was 15-20 miles of virtually traffic-free dream territory lying ahead. Add to this a felt 50 miles of visibility and you’re on the threshold of driver’s paradise. It’s the perfect place to showcase just how much the hot hatch has changed: in 1976 the first VW Golf GTI had 110bhp; the new Mk7 GTI has 217bhp; but now this mad AMG Merc has 355bhp.

Tell me about the mad Mercedes A45 AMG’s hardware

To turn this torque punch into a mighty kick in the butt, Mercedes has mated its reinforced seven-speed twin-clutch transmission to an aggressively tuned 4Matic driveline. The software of the Speedshift ’box is borrowed from the SLS AMG GT, which is why the sportiest A-class features a computer-generated heel-and-toe downshift action, a Racestart function and, in Manual and Sport settings, the same ultra-quick shifts as the flagship gullwing supercar. In C (for Controlled Efficiency), Friends of the Earth may relish start/stop and super-smooth gearchanges at low revs. In S, the same process is repeated at a brisker pace. In M, you play the paddle piano, so don’t expect the black box to help out when the needle of the rev counter suddenly hits its 6250rpm limit. But the transmission will not accept early downshift orders. It will only shift down when it reckons that the revolutions are evenly matched, which definitely takes too long on the fast approach to a slow bend. It’s a fault that afflicts every AMG, from A45 to SLS, to varying degrees.

What’s the A45 AMG like to drive?

Did the SLS-inspired A45 AMG convince us with a rapid-fire throttle response? Yes and no. In combination with the new sports exhaust (with a continuously adjustable flap pinched from the SLK55 AMG) the twin-scroll turbo (which runs at a high 1.8bar) swings the whip hard and early, and when you’re deep in the rev range there’s no issue with throttle response. But it’s the ’box which can undermine this effort by sometimes preselecting the wrong ratio, by taking a little too long to make up its electronic mind now and then, and by occasionally triggering a counter-productive upshift. A software issue perhaps, but one that needs addressing.

On a different front, the AMG computer chips do a splendid job relaying a hackle-raising sensation of speed. By momentarily retarding ignition and injection, they make lead-footed all-out upshifts bark as angrily as the SLS’s V8, they voice an angry blat-blat during downshifts, and they telegraph a catchy cocktail of ’charger whine and wastegate whistle into the cabin. It’s artificial, but rather nice. And there’s bite to match the bark: with Racestart active, this 1480kg A-class will howl in 4.6sec from 0-62mph, officially return around 40mpg, and if you spend a small fortune on the AMG Driver’s Pack, the top speed rises from 155 to 169mph, which almost equals the engine’s cut-out speed. It doesn’t feel as manically fast as the most extreme Evos and Scoobys of old, or gap the Audi and BMW with quite the ease you’d expect, but there’s no doubting the punch of that little four-pot.

The engine delivers quantifiable extra urge with real authority, the steering fuses input and feedback to a wonderfully three-dimensional level of control, the four-wheel drive distributes torque with the eerie professionalism of a poker ace dealing his rounds, and the brakes bite with vigour and determination until, at the foot of the pass, smoke signals beg for mercy. The A45 AMG is as chuckable as it is sure-footed. It can corner on three wheels, decelerate at a ridiculous yaw angle, and put the power down even earlier than the Audi.
What it cannot do is ride well, period. Even on smooth blacktop it is patently obvious that eiderdowns were not on the shopping list. Worse, this is on relatively smooth roads in mainland Europe, yet CAR’s long-term A-class diesel already struggles on broken British Tarmac. And unless you’ve got a crush on your osteopath, stay away from the optional AMG Performance suspension, which features even tauter spring and damper tuning. We’d like more weight from the steering wheel during fast cornering too, and matt pewter paint aside, for the A45 to look less like any other A-class with the optional AMG bodykit.

How does the Audi S3 compare?

The rivals? As luck would have it, not all cars arrived in the required specification, which resulted in the widest possible variety of drivetrain and suspension options. Our S3 was one of the few specimens not fitted with the desirable dual-clutch S-tronic transmission. The manual shifter works well – short throws, positive action, pragmatically spaced gears – but at 5.2sec to 62mph it loses four-tenths to the paddle-shift equivalent simply by taking more time to pass on the slices of the nicely stacked torque cake. At 280lb ft, the turbocharged 2.0-litre unit is not quite as well endowed as its rivals, and yet it rolls out the dough all the way from 1800 to 5500rpm.

WRX STI and Evo IX ran turbochargers the size of an infant’s head, causing serious throttle lag followed by even more serious forward thrust. In the wake of these two wild, winged warriors the motor industry has learned a lot about the art of turbocharging, virtually eliminating delay to throttle orders in the process. At least that’s what we thought before setting off on the trails of Hannibal in these highly tuned triplets. No more turbo lag? Hop into the S3 and the ancient vice is back, large as life and annoying. The extra-cost S-tronic may to an extent cushion the effect, but in the manual version one must change down early to keep at least the bottom two LEDs of the boost gauge lit most of the time.

Which is a shame because after the delay there is always enough oomph on tap to zoom the car towards the next apex. It takes an adjustment in attitude and timing to step on the gas earlier so that little momentum is lost when Snow White is propelling herself onto the next straight. Perhaps this occasionally blurred communication between accelerator and engine control is partly due to the fact that the 2.0 TFSI unit blends direct injection (at low and high loads) with indirect injection (at part loads).

After the A45 the throttle response feels lax, and the brakes bite more sharply but without the AMG’s potency, but at ten-tenths pace the S3 is so easy to drive. The M135i will want to understeer into a corner and oversteer at the exit, but the Audi goes round bends like a slot racer with a second pin between the rear wheels. Neutrality is the name of its game. Boring? Wrong term. The S3 rewards its driver with a different pot-pourri of talents. The roadholding is so tenacious, and although the steering is overly light and a little mum (no matter how you set the weighting via the Drive Select menu) it nonetheless turns honing the line into a surprisingly entertaining pastime. Plus the easy-to-modulate brakes are strong enough to push the point of no return way past the apex, and thanks to these super-sharp anchors, the reassuring tyre grip, the low kerbweight, and a guardian angel named Quattro, the 296bhp S3 can stay in touch with its 316bhp and 355bhp challengers. Up to a point. Eventually, the gap will widen and the Audi will drop back, yet still gracefully maintain its composure. Especially at a 10/10 pace, the S3 is even easier to drive than the BMW.

Is the ‘M-Performance’ 1-series a poor relation?

The M135i feels significantly softer edged than the now-defunct 335bhp 1-series M Coupe. That little bruiser, mixing the M3’s suspension and brakes with a squat chassis, manual gearbox and punchy turbo engine was a riotous experience, but the M135i is different. Believe it or not, but the high-end 1-series makes the charismatic 1M Coupe pale in more ways than one. How come? Because this half-breed M car is benign instead of brutal, cossetting instead of crash-bang hard, relaxed instead of highly strung, easily accessible instead of radically focused.
Through the countless hairpins, up steep slopes, and on a very mixed bag of winding roads, the absence of driven front wheels and a limited-slip differential looked at the beginning of our drive like a deciding dynamic deficiency of the BMW – but we were wrong. Thanks to its good dynamic weight distribution, the chip-controlled traction management and those fine composed-to-order Michelin Pilot Supersport tyres, the semi-M car rarely put a foot wrong. 

That engine is sweeter than apfelstrudel with cream, whipping eagerly through the revs, the mighty mid-range urge putting the four-cylinder competition into perspective, the two extra cylinders of the straight-six ensuring there are absolutely no artificial ingredients involved in making this 3.0-litre motor sound spine-tinglingly good when the mixture gates open. The optional eight-speed automatic cracks quickly through the upshifts too, is keener to downshift than the Merc’s dual-clutch ’box, and hides any trace of turbo lag. And the BMW also is clearly the most comfortable car in this group: even with the driving experience selector in Sport or Sport Plus, the suspension will soak up most vagaries with a smile.

But marketing calls these niche models M Performance Automobiles, and that’s exactly what the M135i is: M make-up plus a performance engine and chassis, all wrapped up in the clothes of a compact gran turismo. The M135i was our number one choice on the poorly maintained Italian autostrada, but it is a touch too laid-back to bring your blood to the boil on those memorable Alpine special stages. Furthermore, the brakes are on the soft side when pushed, the quick steering (only two turns from lock to lock) feels overdamped and under-transparent, and there is more roll and pitch and dive than we expected from a 1-series model wearing the M badge. Full marks for ride quality, panache and refinement, but only 3.5 stars out of five for absolute sportiness and driver involvement.

Would the M135i have won if it looked better and felt more special inside? It might have come closer, but it would still be more of a GT – and we still wonder how the 1-series was ever type-approved for daytime operation on public roads. Thankfully a facelift will right that particular wrong in 2014. The Audi? It is tight-lipped, monosyllabic and reserved, strangely robotic in the way it performs, and flawed in its ability to turn a near-faultless performance into a tangible feelgood experience. There are too many layers of indifference and artificiality in what is, in essence, a solid concept.


It means, after 48 hours, 500-odd miles, 269 litres of premium unleaded, and three fresh shirts, the A45 AMG takes the trophy ahead of the BMW and the Audi, off-putting price tag notwithstanding. The M135i feels like a neatly spiced up 1-series, the S3 feels like an S-line A3 with more poke. In contrast, the A45 feels more AMG than A-class, more special than mainstream, more bespoke than bespoilered. For the time being, this Mercedes rules the microcosm that was once owned by Scooby, Mitsu & friends. But as soon as the 355bhp M2 and the next 375bhp RS3 are ready to pick up the gauntlet, we shall return to these dream driving roads for an encore.