Alfa Romeo Giulia Quadrifoglio vs Mercedes-AMG C63 S: super saloon twin test

Anyway, enough pleasantries. Now to the small matter of Turin versus Affalterbach; great white hope versus reigning power. It’s that Alfa against the formidable Mercedes-AMG C63 S saloon. Get ready for burnt rubber.

We’ve taken the liberty of simplifying this exercise, partly because the brilliant handling that the Giulia displayed on our first acquaintance with it so clearly merited a shot at what we consider to be the best car in the Quadrifoglio’s class. A BMW M3 or a Lexus GS F in the mix might have provided a neat coverline and some easier meat for the new kid, but so what? For Alfa Romeo, only an unequivocal demonstration that the dynamic capabilities, performance attributes and mechanical lures of its flagship Alfa Romeo Giulia amount to more than those of the hottest Mercedes-Benz C-Class will be enough to back up all the big talk. Only that will prove here and now that the greatest sporting passenger cars in the world can once again be made in Italy. 

Alfa is evidently serious about proving such things, because the Giulia Quadrifoglio enters this test with every bit as much horsepower on paper as the C63 S. It’s carrying 75kg less kerb weight and has double wishbone front suspension, a carbonfibre propshaft and an active differential – all ingredients likely to earn a nod of approval from Alfa’s opposite-number engineers at AMG.

But the Alfa’s twin-turbocharged 2.9-litre V6 faces a twin-turbo 4.0-litre V8 today, and an AMG V8 at that. AMG is widely renowned for ‘giving good engine’. If an epitaph for the company were ever needed, that could be it. The Giulia’s engine isn’t lacking in pedigree, though, being from the maker of some of the finest V6s ever to grace any car and also being ‘inspired’ by (or closely related to, depending on who you ask) the V8 in the current Ferrari California. And Ferrari V6 versus AMG V8 sounds like a very fair competition to me.

A great engine is of huge importance to a fast saloon, I reckon. It can make a reputation, it can redeem an otherwise prosaic and reserved car, and it should always dominate the driving experience. And the turbo V8 powering the C63 S is nothing short of a great engine. It so plainly goes above and beyond what most sports saloon engines can do that its stature is beyond question. It sounds brilliant. It’s outstandingly powerful. It has a spectacularly good style of delivery. And it knows about good cruising manners, too.

But the really head-scrambling thing about this engine is how unstressed it seems. Its well of torque is not just fathoms deep but also ocean wide. You can delve into it at almost any crank speed, and when you do, the swell of acceleration on which the car is carried arrives in such timely fashion, perfectly matched to the pedal input you’ve just applied, that the engine barely feels turbocharged at all.

Except that it would have to be turbocharged; no atmospheric engine could come up with that much torque. The woofle and roar that accompanies its ire is rich, authentic and wonderful. The sheer ferocity of the V8 as the needle passes 5000rpm is incredible, too. Strength is heaped upon strength, until the absolute supremacy of the C63’s powertrain is as plain as the three-pointed star on its radiator grille.

A BMW 3.0-litre turbo straight six can’t live with the pressure this mighty V8 exerts, or the many high standards it sets. Neither can Lexus’s 5.0-litre atmospheric F-branded V8. And, as it turns out, neither can Alfa’s new turbo V6. That’s setback number one for the Giulia Quadrifoglio: its Ferrari-related engine may be good, but it’s not magic.

Drive the Alfa in isolation and you certainly wouldn’t complain about such things. But in direct comparison with the Mercedes-AMG, the Giulia’s throttle response is soft, the breadth of its powerband is relatively narrow, the richness of its combustive soundtrack is wanting something and the outright potency of its performance comes up just a little bit short. 

Such things are to be expected when an engine with less swept volume and fewer cylinders is tasked with making the same power as a larger one. Nonetheless, when you read ‘503bhp’ against the vital statistics of both of these cars, you disregard that which you know to be true about engine design and somehow expect parity in what they bring under the bonnet. You shouldn’t. Of course you shouldn’t.

In the real world, you have to wait for a second or two for the Alfa’s midrange thrust to rush in behind the position of your flexed right foot, as the rev needle sweeps up somewhat lazily to 3000rpm, only to then surge towards 4000rpm and on to 7000rpm in a frenzy of industry but without the sledgehammer force of the AMG. And although the rasp of the V6 is loud and multi-tonal when Race mode is selected on the Alfa’s customary DNA rotary mode selector, it does come across as a little flatulent and contrived at times. You’d stop a long way short of calling it sweet-sounding by Alfa’s own exceptional standards.

At Alfa’s request, we didn’t performance test the Quadrifoglio – and wouldn’t have got a definitive set of numbers even if we had. A car with a six-speed manual gearbox was all that Turin could provide, and given that all official UK cars will be eightspeed autos, it’s better that its date with our timing gear comes later.

But here’s the next hole in the Cloverleaf’s boat: on this evidence, I think it would be unrealistic to expect the car to go quicker than the C63 S. Perhaps more concerning, I think it would be equally unrealistic to expect it to match Alfa’s 3.9sec 0-62mph claim. In the real world, it just doesn’t feel quite that quick.

On a dry surface and with a nearperfect getaway, I’ve been witness to a C63 S knocking out a 4.1sec 0-60mph run – not in this test, but only last year, when the C63 S beat an M3 and a Vauxhall VXR8 GTS and proved itself our current super-saloon class champion. And the Mercedes feels like a much more potent car than the Alfa. 

It’s perhaps doubtful that Quadrifoglio buyers would list outright pace as the aspect that attracted them most to their new car. More likely, they’d be after the best-handling sports saloon on the block, and handling is what we’re coming to next. Even so, performance cars should be capable of making good on their manufacturer’s claims. For now, it’s only a hunch, but I’m not convinced that this one will.

But make of that what you will. It’s more important that the Giulia makes good on Alfa’s intent to restore its reputation as the maker of great-handling rear-driven performance cars. And there’s mostly very good news for Alfa diehards on that front: sure enough, the Quadrifoglio does outhandle the C63 S on a flat and smooth stretch of serpentine road. Its handling response is crisper, its roll control and grip level are greater and the cornering balance is marginally sweeter. It feels every inch the lighter, keener, pointier saloon of the two. That’s a victory for Italy – only one, but a hugely significant one.

But, truth be told, both cars are fabulously engaging, almost equally direct and precise, supremely poised and wonderfully flattering things when you begin to approach their adhesive limits. Both are magnitudes better to drive than you might expect any four-door family car could be. And where it loses out by a hair’s breadth to the Alfa as detailed, the Mercedes-AMG hits back with better control feedback and defter damping as the car’s body movements become more exaggerated and the road’s surface more testing.

Is the Giulia the better driver’s car overall? It’s close enough to come down to personal taste – but for me, not quite. It’s more habitable than the C63 S, the coarseness of the AMG’s ride testing your enthusiasm for it at times. It’s also a better handler on its own terms, but not over a typical British B-road, where the relative lightness of the Alfa’s steering and the occasional vagueness of its vertical body control can’t beat the brilliant weight and feel of the Mercedes’ hydraulically assisted steering and the unerring consistency of its damping.

The C63 S is an unapologetically hardcore saloon whose rougher edges you embrace like the burn in your throat that comes between swallowing a slug of good single-malt whisky and feeling it warming your cockles. So rigid are the car’s rear suspension mountings that a student of Braille could probably read the maker’s mark off every manhole cover and drain grate going under its wheels. Yet it’s not an uncomfortable car. The spring rates are well judged and the adaptive dampers capable of compliance as well as dependable cradling support. And the sense of connectedness with the road flowing through both the seat and the wheel is so remarkable that it wouldn’t disgrace a Lotus sports car.

And so Italy will have to be content with runner-up spot here, its sporting debutant losing out to a machine of quite awe-inspiring abilities that has already batted away the challenge of much more established rivals on these pages, built by the outfit whose cars have been the most consistently brilliant performance saloons and estate cars of the past decade. There’s absolutely no shame in that, by the way. AMG beats Alfa Romeo, but Turin gains more from even contending – and contending well – than Affalterbach does from one more success among many. 

Mercedes-AMG C63 S - Mighty powerplant, tactile controls and balanced, biddable handling combine with Merc’s numerous other ownership qualities. Unbeatable.

Rating 4.5/5; Price £67,450; Engine V8, 3982cc, twin-turbo, petrol; Power 503bhp at 5500rpm; Torque 516lb ft at 1750rpm; Power to weight 304bhp per tonne; 0-62mph 4.0sec; Top speed 155mph (limited); Gearbox 7-spd automatic; Kerb weight 1655kg; Economy 34.4mpg (combined); CO2/tax band 192g/km, 35%

Alfa Romeo Giulia Quadrifoglio - Handling lives up to the hype, but the engine, ride, steering and cabin quality aren’t quite on the AMG’s level. Typically alluring and likeable, though.