Depending on your point of view, the fast station wagon is either automotive perfection, or as pointless as ordering a Diet Coke at McDonalds.
Its detractors will argue there’s no point giving a family car head-banging performance, as you’ll simply end up with a spouse that wants a divorce, children floating in a sea of vomit and a dog that looks like it’s been three rounds in a tumble dryer.
For those on the other side of the ledger, fast wagons provide hope. They prove petrolheads needn’t be punished for procreation, that needing space for prams and baby seats doesn’t mean spending the rest of your driving days in a beige people mover.
Fast wagons allow you to not only have your cake and eat it too, but hit 100km/h in less than five seconds while doing so. No prizes for guessing which viewpoint we subscribe to – fast wagons bloody rock.
There’s an extra reason to celebrate the two cars we’ve gathered together for this test: both Audi’s RS4 Avant and the Mercedes-Benz C63 AMG Edition 507 Estate (snappy title, huh?) house two of the finest naturally-aspirated V8 engines ever built, a formula that’s increasingly going the way of the dodo.
AMG has already confirmed the next C63 will be turbocharged, and it’d be a brave punter that bet against Audi following BMW’s lead in downsizing to a force-fed six-cylinder for the next generation of RS models.
Which will be a crying shame, as the 331kW/430Nm 4.2-litre unit in the B8 RS4 is a work of art. How the boffins from Ingolstadt managed to get an undersquare engine to rev to 8250rpm only they know, but the advantage of the long-stroke layout is great low-end response – you could never exceed 5000rpm and still cover ground seriously quickly.
But to do so would be to deny yourself access to the RS4’s incredible top end. Above five grand the tacho needle charges towards the redline, the engine note hardening from a guttural growl to a feral scream. It feels like it could rev forever, so it comes as a surprise when it begins to stutter against the limiter.
Unfortunately, our performance figures were recorded while Victoria was baking in a summer heatwave, and the Audi seemed to suffer most from the 35-degree plus temperatures. If you’ve ever entered a sauna and found it almost impossible to breathe, then you have some idea of the conditions these cars were facing.
Despite using launch control, the RS4 bogs down off the line, costing it a couple of tenths, before recovering to hit 100km/h in 4.93sec and through the quarter in 13.08sec at 173km/h. Each successive run was a tenth slower, suggesting the cooler the conditions, the better it’ll do against the stopwatch.
The Mercedes was no doubt similarly affected by the heat, but it sure didn’t feel like it from the driver’s seat. AMG’s Race Start system allows clean getaways with just the right amount of wheelspin for 0-100km/h in 4.72sec and a 12.83sec quarter mile at an Audi-crushing 182km/h. That the C63 is 0.3sec behind at 40km/h yet over two seconds faster to 190km/h illustrates just how much faster it is than its fellow German on the strip.
Of course, a regular C63 is pretty handy in a straight line.
Adding the Performance Pack just makes it more impressive and the new ‘Edition 507’ upgrades make it borderline psychotic. Forged pistons from the SLS, new connecting rods and a lighter crankshaft have reduced inertia and lifted outputs to 373kW/610Nm. The mods give the Merc’s 6.2-litre V8 the top-end to match its monstrous mid-range.
Getting all this power to the ground is another matter, a problem exacerbated by no longer being able to option yourself a limited-slip diff in the C63 wagon. With measly 255/30 ZR19 tyres at the rear, grip is easily overwhelmed in the first three gears, the inside rear tyre furiously spinning the power away.
The lack of a proper diff also robs the handling of some predictability, which is all the more frustrating considering the rest of the package is so good.
Initially the Merc feels quite soft, diving under brakes and rolling in corners, but the balance of the chassis and communication through the steering gives you the confidence to throw this family wagon around like a 500hp Toyota 86.
While turn-in is sharp and the rear-end very agile, it telegraphs its movements so clearly it never feels wayward, just brilliant fun. Relatively skinny rubber (the fronts are just 235mm wide) means grip levels aren’t high, but like all the best driver’s cars it gives you options: neat and tidy or wild and lairy.
In contrast, the Audi isn’t interested in options; it simply wants to get down the road as quickly as possible. With all its settings in ‘Comfort’ it bobs along serenely, engine burbling away quietly, but switch the systems to ‘Dynamic’ and the whole car stiffens, like you’ve filled its fuel lines with Red Bull.
Body roll is banished, occupant comfort ignored, the RS4 dealing with bumps by simply pummelling them into submission.With 265/30 ZR20 rubber all ’round, it has huge reserves of grip, and the optional sports differential banishes the understeer that dogged Audis of old.
Any front-end push can be countered with more throttle, the power shuffling to the outside rear wheel to pivot the whole car towards the corner exit. Get your entry speed right and you can get hard on the gas pre-apex, firing out of a bend at max rpm and leaving the C63 in your dust.
But while the Audi’s limits are high, finding them is more difficult – you’re never quite sure how much grip is left in the front end. Its variable-ratio steering is super fast at just 2.2 turns lock-to-lock, but turn-in isn’t as sharp as the Mercedes and it’s more difficult to place on the road.
Part of the problem is that while the RS4’s Drive Select system offers a choice of steering and suspension modes, none of them are quite right. In Comfort the steering is alarmingly light but the added weight in Dynamic makes it feel like you’ve run out of power steering fluid. Similarly, setting the dampers to Comfort translates into too much body roll in the bends, but switching to Dynamic makes the ride almost intolerable.
In theory, this duality should offer the best of both worlds, yet in reality it feels a bit ‘jack of all trades, master of none’; too often you’re searching for a setting somewhere in the middle.
The C63’s set-up would provide a good benchmark. As mentioned, its hydraulically-assisted steering is beautifully communicative, while the fixed rate damping is superb. It’s on the firm side, sure, but it filters out most of the annoying road imperfections and keeps the hefty 1795kg kerb weight under strict control.
The Mercedes doesn’t have it all its own way, though. Despite similar on-paper specs, the Audi’s brakes are superior in power and feel, and its dual-clutch gearbox feels a generation ahead of the C63’s occasionally recalcitrant wet-clutch auto, the DSG’s lightning shifts making it the perfect partner for that incredible V8.
Would a six-speed manual improve the driving experience? In this case, I’m not sure it would. Only some pretty agricultural low-speed behaviour, particularly when coming to a stop in manual mode, marks it down.
Agricultural isn’t a word you’d use to describe the Audi’s interior, though. Despite being based on a humble A4, everything you see and touch feels and looks expensive and the low-slung driving position is spot-on.
A word of warning, however, about optioning the RS bucket seats. They’re superbly supportive, but about as easy to get in and out of as Alcatraz – before it became a tourist destination. Driving the Merc feels like sitting on a bar stool in comparison, but with the all-new C-Class arriving later this year, things might not be so clear cut for long.
Looks, of course, are subjective, but to my eyes the Audi gets the nod here as well. To the uninitiated it looks just like another Audi wagon, but you’ll receive knowing nods of appreciation from those who’ve spotted the pumped guards and signature silver door mirrors.
The C63, on the other hand, is about as subtle as a Metallica concert. Adding side stripes and the bonnet from the C63 Black Series has ramped up the aggression quota but the overall effect’s like a bodybuilder who doesn’t know when to stop taking steroids.
So having traded blow after blow, which one takes the title? The RS4 is mind-blowingly capable and you’d never, ever tire of the way that V8 screams towards redline, but driving it hard quickly becomes an exercise in ‘how fast can I go?’ rather than ‘how much fun can I have?’ It’s impressive, but fails to reach the dizzying heights of its predecessor or, indeed, its bigger brother, the RS6.
Which leaves the C63. It’s feeling its age in certain areas, but the combination of that engine in that chassis creates a driving experience that has few peers when it comes to putting a smile on your face.
The doyen of sports commentary, Bruce McAvaney, would call it ‘special’. We’d call it bloody awesome. Think of it like this: if the RS4 is Sebastian Vettel, then the C63 is Mark Webber. One is undoubtedly faster and probably technically better, but I know which one I’d rather share a beer with.