Audi RS4 vs BMW M3 2008 Comparison

January, 2008

"Are you the blokes with the M3 and RS4?" Barely waiting for a reply, our new friend pulled up a chair.

"I've just ordered a new M3," he breathlessly admitted, "and would love to hear what you think."

By the time our cool-beyond-measure super-sedans rumbled out of Ulladulla, on the NSW south coast, we'd established that Alan personified the aspirational heartland of muscle motoring. After various V8 Statesmen, two HSVs - including his current GTO - plus a 6.0-litre Calais V as daily wheels, Alan craved a change. The lure of Euro-tech, plus a hint of premium-badge envy, had enticed him to BMW's new V8 screamer.

Now, just two days after confirming his order - with delivery not before June 2008 - anticipation nerves had set in. Should he stick with the manual gearbox, or take a chance with the latest SMG-style tranny that would, according to the dealer, put back his M3 to September or October? Or about the time the M3 sedan arrives. Alan, in love with the coupe flair, had discarded the RS4 from his search, but was the Audi worth a second look? Uncertainty building, Wheels had rolled into town.

Who better to ask?

Head-to-head testing on some of the best driving roads on the planet, roads seemingly created for pace notes, had finally thrown up a definitive answer. But, we assured Alan, drive either of these potentially intimidating, yet practical, powerhouse machines and you'll wonder if anybody really needs an exotic supercar. We'd have happily parked either car in our fantasy garage, except by then we knew that one would make us just a tad happier. Which one? Well, that's what this story, and our conversation with Alan, set out to explain.

So broadly talented was the recently departed E46 M3 that when Audi set out to beat its arch rival, the company adopted a similar philosophy, adding a monstrously powerful engine with two extra cylinders and the trademark all-wheel drive. The engineers had learned their lessons well, for nothing Ingolstadt has done since the original Quattro - except, perhaps, the even newer R8 supercar - has been as convincing.

This is not your conventional comparison test - the RS4 is now out of production, with the twin-turbo V10 RS6 due in July and a new RS4 not before 2010 - but the rivalry between the standard-setting Audi and the new M3 is so obvious, so compelling, we couldn't wait for the March '08 arrival of the Mercedes C63 - AMG's challenger for the same crown - or the much-anticipated V8 Lexus IS-F. Besides, for a lucky few, there are still some RS4 sedans and Avant wagons to be found in local showrooms.

Nothing better illustrates the competitive relationship between the $164,500 RS4 and $157,000 M3 than their respective power outputs. You guessed it - both make the same 309kW. The all-new 4.0-litre BMW V8 (replacing the 24-valve inline six that served the M division so effectively for more than two decades), is derived from the M5's V10, hits peak power at 8300rpm and develops 400Nm at 3900rpm. Audi's direct-injection 4.2-litre V8 muscle is generated at 7800rpm, and its torque of 430Nm at a deceptively high 5500rpm. Significantly, in terms of the engine's astonishing flexibility, it also makes at least 400Nm all the way from 2250rpm to 7600rpm.

Not to be outdone, the BMW V8 produces 85 percent of its maximum torque (340Nm) across a remarkable spread of 6500rpm. In a neat touch, aimed at protecting their sophisticated internals, both provide oil temperature gauges - precise to the nearest degree - and lower the redline until the engine is properly warmed.

However you evaluate these rival V8s, they rank among the great road-car engines of this era. So characterful and muscular at 8000rpm plus, yet tranquil and effortless at low revs, despite the menace of their evocative idle notes. Especially the Audi. Courtesy of modern electronics, fuel injection and variable valve timing, both offer exceptional tractability - as proved by their capacity to accelerate from 1000rpm in sixth gear; no hesitation, no driveline shunt. In one final attempt to upset the RS4, we ran its V8 down to 500rpm in sixth (that's below idle) and still it pulled cleanly. Up hill.

The M3 is shaded by the RS4 in low to mid-range acceleration where the Audi has a small, but discernible performance advantage. Over the last 2500rpm to the 8400rpm cutout, where the M3 does its explosive best work, the Beemer gradually begins to win back the lead. We're talking nuances here, but the M3 V8's character is a touch more sporting, the Audi more linear, in its power delivery - which helps explain why, at eight-tenths or more, you always prefer to be one gear lower in the RS4. Telling, when the overall gearing is near identical.

Mechanically, the major difference between the two is instantly obvious when launching them on the track. On the RS4, as usual for a high-performance Audi, power reaches the road via a (new-generation) Quattro four-wheel-drive system. No dramas, no excess of wheelspin, just feed in the clutch at 5500rpm and the RS4 takes off, chirping all four wheels and dispatching the Oran Park straight damned near as quickly as a 911 Carrera S. For both, we're talking 0-400 metres in the very low 13s and 5.1sec to 100km/h.

The M3 - rear drive of course - is entirely more complex, courtesy of an iDrive-controlled chassis set-up that offers the choice of three stability control modes. Try a launch with the DSC active and the engine bogs down, regardless of the revs. Switch off the electronic intervention and even 2500rpm instantly lights up the rear wheels, tacho needle quickly bouncing off the cutout in first and second, clutch slipping in sympathy.

Overall, however, the acceleration numbers are so close that any differences count for nothing on the road.

If the surface is slippery, the RS4's 70kg extra mass (1650kg versus the M3's 1580kg) is offset by the benefit of all-wheel-drive traction. Where the Audi confidently puts down all its power, regardless of DSC setting, the M3's stability control light is constantly flashing on the same blacktop. Nothing the M3 can do, wet or dry, matches the Audi's traction out of a second-gear hairpin. In normal conditions, the RS4 sends 40 percent of drive to the front wheels, 60 percent to the rear, but the spread varies from 65 percent to the fronts and as much as 85 percent to the rears, depending on how the car's sensors read the conditions.

Mostly, the set-up does a brilliant job of disguising the RS4's 60 percent front-end weights bias, and you're left asking why other Audis don't change direction with the same fluency. In isolation, because it rides, handles and, miraculously (this is an Audi) also steers with precision, the RS4 feels so naturally balanced that you're hard pressed to detect the extra weight over the nose.

When you belt the M3 - 51 percent mass over the front wheels - through the same series of dry, twisting mountain roads, the steering only gets better, more precise, the harder you drive. The Beemer always asks for less steering lock, allowing the driver to adjust the neutral chassis balance millimetre by millimetre via the throttle, a technique which quickly becomes an incredibly rewarding reflex action. The RS4 is slower to turn in to corners, and often hints at understeer where there is none in the M3. The preferred M Dynamic mode allows the driver to lean on the M3's outside rear wheel, balancing the car on the throttle to counter any front- end push or oversteer. Turn off the DSC completely and the M3 demands concentration and immense talent, despite the exceptional grip of specifically developed 18-inch (19s are optional) Michelin Pilot Sport rubber, if all that eruption of top-end power is to be exploited. Save the tyre-shredding, opposite-lock oversteer - utterly inappropriate (and slower) on the road - for track days, but be prepared to fund Michelin's executive bonuses. Brakes? Mighty stopping power, but the pedal travel on both is longer and less confident in feel than expected.

For the M3, BMW has separated the damper settings from the power (no extra kWs, like the M5, but a sharper throttle), steering and stability control choices. It's a canny decision that brings massive benefits on our lousy roads. In the comfort (softest) damper setting the M3 rides brilliantly, soaking up the worst irregularities and coping with bumps that so upset the chassis in the Sport setting that it really should be reserved for the track. Even in the intermediate 'normal' mode, the M3 ride is more comfortable than the taut RS4 and, surprisingly, the sister 335i Coupe, and brings an obviously tighter control of body masses.

The trade-off in 'comfort' is a slight reduction in body control, but since it's possible to save all your preferred selections, via the iDrive menus, to the M button on the steering wheel, swapping between the settings is painless. Debate over the two steering- weight settings is a contentious issue among Wheels' testers. Some find the light mode too vague, but I prefer its extra sensitivity to the heavier setting that adds nothing in the way of genuine feel, but does definitely detract from the car's low-speed handling fluency and communication.

In general, however, the M3 controls are firmer, heavier, than those of the RS4. Regardless of the BMW's settings, the Audi steering is lighter, feels quicker at low speeds and has none of the on-centre remoteness that has been an unwelcome Audi trait for decades. Clutch take-up is less progressive on the M3 and, because the gear change is also notchy, the BMW is slightly harder to drive smoothly in traffic. Which makes the M3's notably superior ride comfort all the more incongruous. The RS4's short, sharp vertical suspension movements mean the ride is fidgety and unsettled. It may be this that contributes to an occasional groan and shake through the body when a fast travelling, and loaded, wheel jars as the suspension copes with a bump or pothole. In these circumstances, the M3's body feels more rigid, which may account for the lack of wind and road noise - both flaws that undermine the RS4's refinement.

On a car with so many layers of technology, an old-fashioned clutch and manual gearbox somehow seem out of place, especially since the M5 only comes with the - admittedly difficult - seven-speed SMG. As Alan's dealer communicated, next year the M3 (and M5 and M6) get a new gearbox. Details are scant, and BMW's saying nothing, but we know the eagerly awaited seven-speed M DCT uses a twin-clutch system, operating through steering wheel mounted paddles, and is expected to answer most of the issues raised by M5's complexity.

BMW takes a surprisingly subtle approach to the M3 interior as there is little to distinguish it from the 335i Coupe. In contrast, the RS4 looks special though, in reality, it doesn't work as well as the M3. Those deep, race-style buckets look brilliant, but so high and hard are the cushion side bolsters that they demand a special egress technique. Tall drivers will quickly discover a lack of lower lumbar support, while their depth drastically cuts into rear-seat knee room. The flat-bottomed steering wheel looks the part, but the lower section's plastic trim is a shoddy touch in an otherwise beautifully finished interior. And why are the seats manually controlled, and why do you need to turn the ignition key - right of the wheel - and then press a button on the central console to start the engine?

If the M3 interior lacks the class of the RS4, it provides a superior working environment. The brilliant front seats are more comfortable, yet offer just as much lateral support, while the rear compartment is more spacious thanks to the less intrusive front buckets. The M3 also gets power seat adjustment (including side support) and a slightly more sporting driving position (though some testers would have preferred the seat to go even lower) than the vaguely rally-ish, over-the-wheel location of the RS4. The M3 starter button is on the dash next to the entry point for the ignition slot; better than the Audi but still an unnecessary gimmick.

We found Alan's card under the M3's wiper after the coffee break.

"When you have time, would you please phone me to discuss your thoughts on the M3?" No need. Alan was happy, though when we left him he was still confused about the gearbox choice.

For us, the decision is a tough one. How do you decide between two sensationally effective and seductively quick road cars?

The M3 wins because, ultimately, it is the superior driving machine - at least on dry roads - with a markedly better ride and because it makes more effective use of the interior space. The margin is so narrow, however, that we still look upon the RS4 as an achievement of the highest order. And envy all those who drive one. Next year, however, it won't be envy, but naked jealousy when our new mate Alan takes delivery of his M3.