new Audi S4

[구태균]

November 11, 2008

2009 Audi S4 First Drive: Pray for Rain
By: Chris Ostberg

For those of you with short attention spans, we'll cut right to the bottom line. The new B8 S4 is better than the old one. The supercharged V6 is better than the V8. The new car is lighter, faster, more fuel efficient, more rewarding to drive and cheaper to boot. The optional rear sport differential rocks - no question. The B8 S4 may be more fun than any other Audi (save for the R8) in the rain. There's no Avant for the US, and that's probably not going to change. Yes, we asked twice. Do we have your attention? Would you like to know more? Perhaps you're skeptical of these bold claims. In any case, keep reading as there's a lot more to the story...

Our experience with the new S4 begins in Majorca, an island in the Mediterranean Sea nestled about halfway between Spain and Africa. With its mild climate, beautiful beaches, and picturesque mountains, Majorca is one of the premiere tourist destinations for many Europeans. Most travelers coming to the island expect clear sunny skies, and anything less could easily be interpreted as the makings of a disappointing vacation. Sun and sand may have been what Audi visualized when planning the launch of their mid-sized sport sedan, the B8 S4, on this Spanish island. Other visitors were undoubtedly irritated after being ambushed by bouts of heavy rainfall. For those of us behind the wheel of the new S4 equipped with a torque vectoring sport rear differential, the rain couldn't have been more welcome.

The B8 platform is the basis of Audi's latest A4, their best selling vehicle. Audi calls the all-new underpinnings a Modular Longitudinal Platform or MLP for short. The brand is banking on a "modular" system, meaning they will be able to share the same basic architecture throughout their model lines (currently A5/S5 with plans for A6/A8) to save on development, tooling and production costs. Perhaps the most notable feature of this platform is the new packaging proportions which are a departure from traditional Audi layout.

The wheelbases of the respective vehicle lines have been lengthened, resulting in less front overhang. Through some creative engineering, Audi has changed the relative locations of the front differential, clutch, and steering rack assemblies in order to push the engine back over 6 inches compared to previous A4/S4 offerings. The resultant effect is a more balanced weight distribution and a reduced polar moment of inertia; the car will be more willing to rotate and eagerly respond to the driver's steering inputs.

After a well received launch of the mainstream A4, Audi's muscular and more exclusive S4 is waiting in the wings to be sent to North American shores late 2009 as a 2010 model. Unlike the transition from the B6 to B7 S4 variants (which was largely cosmetic changes), the B8 takes the concept of a mid sized all-weather sports sedan in an entirely new direction. The revised MLP platform has improved weight distribution to 55F-45R. Instead of the previous 4.2 liter 344 hp V8, the B8 S4 is propelled by a 333 hp FSI 3.0 liter V6 with an Eaton 4-vane Roots belt driven supercharger nestled cozily between the 90-degree cylinder banks. Audi has oddly dubbed this engine as a 3.0T ("T" has typically stood for exhaust driven turbocharging in Audi's nomenclature) despite forcefully engulfing air with a "Kompressor".

Yes, you read that correctly. The new and supposedly "improved" B8 S4 is down 11 thoroughbred Deutsche Pferde right out of the gate when compared to the outgoing V8 model.

"What's the point of that?" you may ask.

Hold on, pause a second, it all makes perfect sense. Long story short, this IS a stronger engine despite the slightly misleading peak output figures. Aside from the last 500 RPM of the useable rev range, the V6 engine is making more power basically everywhere. The supercharged V6 has a flat torque plateau of 325 lb-ft starting at 2,900 and carrying out to 5,300 RPM. Looking at the two output curves overlaid below, one can easily see that the V6 engine is creating more horsepower and more torque at nearly every RPM point compared to the normally aspirated 4.2 liter V8. The end effect is a more responsive engine. Area under the power curve is the secret here.

A broader torque curve is not the only motivation for the smaller force-fed engine. With increasing emphasis on global greenhouse emissions and reducing fuel consumption, all major automakers have been working on engine downsizing. The concept of downsizing is simple: use a lower displacement engine with forced induction to generate the power of a large engine and the fuel consumption of a smaller one. Besides an absolute improvement in efficiency, the yearly taxation benefit in many countries outside of the US (which tax vehicles according to engine size) can equate to hundreds of dollars or more.

Audi is one of the pioneers of this downsizing design strategy as seen in the original 1.8T. Modern technologies like direct gasoline injection and advancements in turbocharging have made this design strategy even more potent. With the 4.2 liter V8 notorious for being a gas guzzler, the decision to "re-downsize" the S4 platform was clear for Audi engineers. According to Audi, the B8 S4 uses 27% (!) less fuel than the V8 powered B7. More performance and drastically lower fuel consumption? Sounds like a winner.

Was this the correct decision? Has Audi abandoned the turbocharger, which has done them so well in the past? According to Audi, a biturbo direct injection version of this engine was developed in parallel. After a long testing and development process, a decisive nod was given to the mechanically supercharged version. The advantages of the mechanical supercharger are plentiful - easier to package, quicker throttle response and boost buildup and overall simplicity.

At the modest power levels and boost pressure targeted by the S4 development team (0.8 bar manifold), the supercharger concept yielded the best overall package, with emphasis on drivability and throttle response. Audi will admit that on higher powered applications (say 400+ hp), the turbocharging solution will be superior. The 580 hp 5.0 liter V10 from the RS6 and the upcoming 4.0 biturbo V8 is proof that Audi hasn't abandoned turbochargers.

Tech minded aficionados will not be disappointed. The Eaton supercharger has 4 lobes with a high angle of twist which greatly boosts thermal efficiency over previous offerings. At rated power, the energy input required to drive the supercharger is just over 20 hp, which is quite good considering the unit is capable of blowing out over 1 ton of air per hour. Twin liquid-to-air intercoolers are housed under the supercharger within the intake manifold. Bosch's latest FSI system is employed boasting 150 bar of injection pressure. Direct gasoline injection allows a high static compression ratio of 10.3:1 to be possible without engine knock.

Further benefits are increased efficiency, power, and off boost response. The closed deck aluminum block (with etched Alusil bores) is very compact and lightweight (73 lbs). Audi has made their own proprietary modifications to the supercharger housing to improve NVH characteristics. The intake camshafts are equipped with a variable valve timing system. Audi's new Valvelift strategy is not employed, perhaps leaving the door open for future output expansion.

All the technology in the world doesn't matter unless the final product delivers what it promises. Admittedly, we were skeptical. We have grown to love the prodigious torque and effortless acceleration that Audi's turbocharged engines of the past are famous for.

My personal car is a biturbo B5 S4 warmed over to the tune of 500 hp, so it takes some muscle under the hood to impress me. Luckily, two days of blasting up and down the Spanish countryside have left me very impressed. Audi has done a great job with this powertrain!

The throttle response is at least as good as the outgoing V8, perhaps better. If you gingerly take the 3.0T up to about 3,000 RPM in first gear and mash the go pedal, you will be drop kicked in the sternum with an immediate surge that no turbocharged car will compete with. It responds NOW. Even the best turbocharged cars, especially at higher power levels, will need a few split seconds to build boost as the torque pours on like heavy molasses. Turbochargers have a delay, superchargers don't. The lack of a cliche supercharger whine will fool many people into thinking there is muted 5.0+ liter engine under the hood. Other than certain light throttle conditions at low revs, one would be hard pressed to identify it.

The near telepathic response is pretty amazing, and admittedly addicting. In what we consider a good decision, the behavior of this engine is not overly dulled electronically. While being refined in nature, it still has a slightly raw feeling to it when pushed hard. Turn off the ESP, and you can light up the tires on a hard 1-2 upshift, especially in the wet. The free revving nature is much quicker than the old 2.7T engine and on par with the RPM-happy V8's. The power delivery does not let up as you approach redline, but it doesn't build to a frantic crescendo like a highly strung normally aspirated car either.

There exists a certain segment of S4 fans who have bought into the platform solely for the V8 experience. Perhaps slightly superficial in their needs, the staccato V8 bark may be a make-or-break feature. For those who can try the car with a logical and open mind, the performance of the supercharged V6 is superior in every aspect...except for the soundtrack, which did leave us a little disappointed. In our opinion, the sound is slightly overmuffled, with an industrial Shop-Vac overtone at full kick. It lacks the authoritative bark of the V8, the mellow and smooth nature of the B5's biturbo V6, or the soul-stirring wail of the inline 5's of yore. Perhaps the aftermarket will find a way to uncork things a little.

On the plus side, S4's equipped with the new S-tronic 7-speed DSG box will be rewarded with playful cracks through the quad tailpipes on the lightning quick upshifts (ignition timing being retarded) or rev matching downshifts so perfect that any human short of the Stig would be unlikely to recreate them. Those 6-speed manual die-hards will be stuck with a less stimulating aural sensation, so you better pony up for the excellent Bang & Olufsen sound system.

When benchmarking other comparable engines, the 3.0T has raised the bar in this mid sized sports sedan segment. A glance at the spec sheet shows you this new engine is competitive; it sports 333 hp and 325 lb-ft of torque which easily puts it ahead of its closest competitor - the BMW 335i twin turbo. At a scant 189 kg (417 lbs), the 3.0T is lighter than the outgoing V8 (195 kg) and on par with the less powerful BMW twin turbo I6 (187 kg). For additional reference, the cast iron block 2.7T tips the scales at 200 kg. The 3.0T is also inches shorter than all three of those engines which is a huge benefit on a quattro equipped vehicle that still has an entire engine hanging forward of the front axle line. Audi promises the new engine will yield better performance and significantly improved fuel efficiency.

Initial engineering estimates predict 17 mpg city/27 mpg highway for the S-tronic 7-speed car, figures the V8 could maybe achieve coasting down the steep side of a mountain pass. With a tailwind. Electing to shift gears on your own will cost you about 1 additional mile per gallon on the highway. Chances are at least one of the S4 variants will be able to drop the gas guzzler tax.

The beefy torque curve and instant throttle response is well matched to either transmission choice. The B8 S4 is Audi's first vehicle to offer a true DSG S-tronic gearbox on a longitudinal vehicle platform (engine oriented North-South). There are 7 well spaced ratios for optimum acceleration, and the 7th gear is taller than the highest ratio found on the manual transmission netting slightly better highway fuel consumption. For those concerned about durability of this complicated gearbox behind a powerful engine, the rated torque capacity of the S-tronic is actually greater than that of the traditional 6-speed manual (369 lb-ft vs 332 lb-ft).

There is no type of "launch control" built into the S-tronic, so acceleration out of the hole isn't breathtaking. Launching above 2,000 RPM is out of the question. However, the shifts are performed blitzkrieg quick which will make up ground on manually shifted cars very expediently. Each new iteration of DSG we've driven is a significant improvement over the previous. We found the shift speed and shift logic of this unit a marked improvement over the TT's transverse DSG. The 6-speed manual is smooth and precise, lacking the rubbery feel of the 335i. We fully expect acceleration figures to be smack-dab between the outgoing B7 S4 and RS4 models. Despite Audi's conservative quoted figures, US magazines (who traditionally use 12" or 0.3 seconds of rollout) should be running about 4.7-4.8 second 0-60 times and dashing through the quarter mile at 13.4@105 mph if our Popometers are still calibrated to TUV specification. You heard it here first.

As good as the new engine is, don't take our gloating the wrong way. Audi's S cars have always been about more than a small car with a powerful engine. The overall package must be well rounded - a veritable decathlete if you will. Fortunately, the driving dynamics of the B8 platform are on par with the new engine - meaning, improved in every category.

Much like Porsche, the very basis of Audi's design concept does bring about dynamic compromises. Front engined cars with quattro still have the entire engine mounted fore of the front axle line creating a nose heavy car. Audi has spent decades taking this inherently flawed idea, and honing it to near perfection. In the past, this often meant that chassis behavior at the limit of adhesion was compromised to some extent. In most situations, factory stock Audis would tend to push or understeer at the limit. Although a safe and predictable response, this left many enthusiasts wanting more control over the rotation of the car at the limit of traction.

Beginning with the B7 RS4, quattro equipped cars started sending more torque to the rear axle than the front under normal conditions. Admittedly a step in the right direction, this was not a radical change in performance. Now Audi has a new technical solution, the "sport differential", which is capable of drastically changing the dynamic response of a nose heavy platform. Using innovative technology to overcome what was previously a shortcoming is what Audi's "Vorsprung duch Technik" tagline is all about.

Simply explained, Audi's quattro sport rear differential is ESP in reverse. A more generic term for this technology is torque vectoring. As we know, ESP (electronic stability control) combines wheel speed, steering angle, and yaw angle sensors to individually brake any of the 4 wheels on the car when a slip angle is detected. Those of us who have made that yellow triangle on the dash illuminate madly know the feeling all too well. Just as the car starts to slide, the electronic nanny steps in and straightens things out while scrubbing off speed. Somehow the same electronic widgetry deployed to harness your speed often manages to take the fun out of the equation at the same time. It's usually a little on the intrusive side. While a good feature for safety, it can easily become a hindrance on the race track or when enjoying an AWD car in slippery conditions. If you're one of those who tends to turn your ESP off as things start to get a little wild, you're a prime candidate for the sport rear differential option.

How does it work? The center section of the differential is surprisingly no different than a traditional open unit. On each outboard side, there is "superimposed gear stage" meaning an overdriven gear capable of turning either of the rear wheels 10% faster than the input speed. Each side has an electronically controlled clutch pack which can engage the "overdrive" gear. The clutch engagement is variable meaning either side can be sped up at any interval between 0 and 10%. This speed differential can send nearly all of the rear axle torque to one side, as long as both wheels are getting traction. The engagement of the differential clutches is dictated by the same sensors which control ESP operation (wheel speed, steering angle, yaw, etc). The behavior of the system can be further altered by the ADS (Audi Drive Select) mode.

End result, by speeding up individual rear wheels, this system can provoke the car to rotate in the same way ESP prevents the car from rotating. The system is active on acceleration and deceleration. Unlike ESP, the system can begin working before slip angle is detected, meaning the operational sensation is seamless and fluid. For an example on how the system would work, imagine negotiating a bend to the right. In this case, the sport differential can speed up the rear left wheel, causing the car to rotate and maintain a neutral cornering characteristic before understeer sets in. It can even induce and control oversteer!

Admittedly, we found the differential to have limited use during normal daily operation. The narrow Spanish roads in Majorca were not a prudent venue to test 10/10 handling characteristics. The level of grip on dry pavement is very high, so creating a traction loss situation on public roads will take bravery, or stupidity, depending on how you look at it. For my driving skillset, it's a heaping portion of the latter. Given a more familiar stretch of road under the right conditions, we would have been more willing to "play" with the car.

It's also worth noting that the sport differential will become active in an emergency maneuver and work with the ESP system to stabilize the car, it's not exclusively for hooligan-like tailslides, drifts, and donuts. Good thing, that'll make our significant others that much more eager to buy into the deal. Safety? Yeah! We NEED that. On the con side, we'd prefer to see a true limited slip or locking mechanism employed in the center section of the rear differential. Although not typical usage, lifting a rear wheel would still result in wheelspin just like with a standard open differential.

Once we reached the small roadcourse named Circuito Mallorca, our impression of the sport rear differential changed substantially. By this time, the sky had become completely overcast as rain bellowed down from above. Audi couldn't have planned the weather any better.

On the rain slicked, tightly wound, yarn-tangle of a circuit, the effects of the sport rear differential were immediately felt. Under braking and backing into corners, a light hand could be felt in the rear helping the car rotate. On corner exit, the throttle could control the cornering attitude of the car, just as much as the steering wheel. Our first 2 laps were completed with the traction control and ESP systems active. This will allow a small slip angle (slight oversteer) before power is reduced and slip angle is eliminated. Once comfortable with the course, we disabled traction control and ESP by holding the button down for a few seconds. Now the fun was on.

THIS is what quattro is all about. The synergic combination of an improved weight distribution (~5% better than previous S4's), rearward torque bias (40:60 static) and the quattro sport rear differential rewards the driver with a chassis dynamic we've never experienced in a front-engined Audi before. The prevailing behavior is quite neutral, with early throttle inputs causing the tail to rotate easily. If one was to come in too hot and induce understeer, the rear differential will work its magic to bring things back to neutral. Get brave, and you can tailslide the B8 S4 nearly as well as a RWD car, with the added control of AWD to send torque forward and straighten the whole mess up on demand. You can look and feel like Walter Rohrl power-sliding the Audi S1 at full opposite lock up Pike's Peak with a fraction of his driving ability.

This differential was flat out amazing in wet conditions. We're willing to bet it would be at least as much fun in snow. Hopefully the system is equally effective on dry tarmac, but unfortunately we were not given the opportunity to verify this. Even if the B8 S4 isn't significantly quicker than its predecessor around handling metrics like the Nürburgring Nordschleife, the improved "at the limit" response is well worth the price of admission. The cost of the sport differential will be about $900, a bargain for those who plan on getting the most out of their S4.

Also adding versatility to the driving experience is Audi's optional ADS system (Audi Drive Select). This electronic network can link the suspension, steering, transmission (if S-tronic), and rear sport differential (if equipped) to tailor the vehicle response to user selectable modes. Four distinct settings are available; Comfort, Auto, Dynamic, and Individual. On the comfort setting, steering input is reduced, the ride is softened, and the ESP/DSG/ and sport differential calibrations take comfort and safety as the number one priority. In the Auto mode, the computer chooses the best settings based on conditions and your driving inputs. Dynamic mode sharpens the steering (quicker ratio, stiffer feedback), quickens DSG shifts, firms up the suspension, and makes the sport rear differential respond more aggressively. Individual allows the user to adjust each individual system independently using the MMI interface. The difference between modes was easily felt. We found dynamic to be the most enjoyable overall choice. Despite a firm, well damped, sporty ride, the body motions were not overly harsh and the more aggressive steering sensations were appreciated.

The rest of the car holds no surprises. The interior quality is top notch, with the two tone seating surfaces (featuring contrasting stitching) found in our test vehicle providing an interesting visual contrast. The MMI interface is intuitive and has a shorter learning curve than BMW's i-Drive system. Ergonomically, the B8 scores very well, with perfectly placed pedals for heel-toe shifting. The HVAC and center console area may be a little congested with controls, but should not pose problems after the user gets acquainted with the environment. The switchgear has a high quality feel and should wear well. The frontal cockpit offers a comfortable driving position with ample room, and the rear seats appear to also feature improved legroom...a long time A4/S4 platform shortcoming.

Visually, the B8 S4 takes the conservative route. There is little to distinguish the S model from the standard A4 trim. Slightly more aggressive bodywork, quad pipe exhaust, sliding brake calipers featuring an S4 cover plate, and more aggressive rubber are the telltale signs. The LED daytime running lights do provide a menacing presence and are becoming a trademark feature of Audi's fleet. Some may find the exterior styling too bland and prefer something more distinctive, though this boils down to personal taste. Our feelings were that the optional 19" RS4 style wheels fit the car much better than the standard 18" wheel package.

Despite being an overall larger car, the weight of the European model promises to be lighter than the outgoing V8 S4. If you believe Audi's preliminary data (which has failed us in the past), the EU spec car weighs in at just over 3,600 lbs. As long as there aren't any surprise DOT mandated binges, we're hoping the US spec car won't be much more than this.

This new platform brings about some interesting propositions on the tuning horizon. The S4 has always been a popular vehicle for those who like to modify their cars above factory spec to suit their desires. Sure, it's expected that power enhancing options like supercharger pulleys, ECU tunes, and exhaust systems will boost engine output to north of 400 hp. That's just a matter of time. What has us intrigued are the new chassis tuning opportunities hidden within the Audi Drive Select and sport quattro rear differential. It's quite feasible that tuners could manipulate the suspension, steering, and rear differentials to a sporting and more aggressive level above what the factory allows. "Race" mode with max rear differential lock, super quick steering, firmed up damping, and DSG launch control? We can only hope *hint hint*.

So what about that beautiful Spanish island? Oh yeah, it was OK. Honestly, we were too busy enjoying the drive to notice much around us. Although a riot to drive on the rain slicked race track, the S4 truly shines as a deceptively fast point-to-point vehicle on real roads. Sure, the new advancements make the B8 S4 more enjoyable to drive at the limit of traction, but few do this on their daily commute. The newfound point-and-squirt torque curve, the confidence inspiring brakes, the improved interior, the tailorable response from the Audi Drive Select system, boy-racer (errr, safety!) appeal of the sport quattro differential, and the real world savings provided by substantially better fuel consumption make the new S4 a formidable performer for almost any driving situation.

Is there any way to sweeten the deal? Sure. How about making it cost less than the outgoing model. European pricing has slated the new B8 S4 at roughly 4,500 Euro less than the current model. North American pricing is still being worked out, but we fully expect the B8 S4 to be competitively priced starting in the mid $40k range.

 

[자미로콰이]

헤드라이트 부분이 약간 bmw7시리즈와 닮은듯한...

[GrayRS4]

앞뒤 무게 배분이 나아 졌다고 하지만 아직도 앞부분이 무겁게 느껴 지네요. 새로운 기술이 많이 적용 됐는데 그중에서도 Sport Differential 기능이 포인트거 같습니다. 뒷바퀴 좌우 토크 배분이 된다고 하는데 얼마나 언더 스티어 현상을 줄이는데 도움을 줄수 있을런지 무척 궁금합니다. 수치상의 기록을 보면 B8 S4가 B7 S4 보다 나은거 같은데 8 기통 타다가 6 기통을 어떻게 탈수 있으런지 모르겠습니다. 귀로 들리는 소리도 운전자를 즐겁게 하는 중요한 소요중에 하나인데 경제적인 문제로 8 기통의 감성을 더이상 못느끼고 듣지 못해서 아쉽습니다.

[클럽아우디]

세월이 흐를수록 이제는 8기통, 10기통 엔진들은 수퍼카에서나 볼 수 있는 희귀 존재가 되겠지요. 경제문제가 대두되면서 과급엔진들이 더욱 기술 발전을 이룰 것 같습니다. B8로 오면서 눈에 띄는 것은 아반트 형의 디자인이 더욱 좋아졌다는 것이네요.