Audi walked away from a certain customer in 2004. Well, that’s what any hardcore forced-induction protagonist will tell you of the late, great “B5” S4’s demise. That particular car was the first S-car to be based on the A4 sedan and powered by a 250-hp twin-turbocharged V6. Back then, the S4 was the step up for rally fiends – a grown-up, higher dollar take on the all-wheel drive turbo genre inspired by the World Rally Championship, which also spawned the likes of the Subaru WRX and the Mitsubishi Lancer EVO. Highly tunable via a rich aftermarket, one could drop a few g’s on an S4 and toy with supercars at the track. And, if you ask the B5 loyalisti, the magic was lost when Ingolstadt shoehorned its burly 4.2 V8 into the B6 generation S4 – faster out of the box, but also more of a GT and with less tuning potential. Going back to forced induction… well, that has everyone talking for sure… from the loyal B5ers to most anyone else looking for a more efficient take on high performance.
Engine and Transmission
At the heart of the new “B8” S4 is a new 3.0-liter V6 fitted with all of Audi’s latest hardware like direct-injection FSI, and then stacked with an Eaton 4-vane roots-style supercharger on top. The setup is good for 333-hp and 324 lb-ft from a wide 2900-5300 rpm. That’s 11-hp down from the outgoing B7, though we all know horsepower doesn’t tell the whole story. Torque goes up 12 lb-ft – increased over a broad range, and that helps explain why the projected 0-62 mph figure for the car 5.1 seconds, which beats the B7’s 5.6 by a half second.
Yes, we know this engine is referred to as the “3.0T”, and there are those “V6T” badges adorning the car’s quarter panels where a chrome V8 was perched last time around. We’re told the letter T now stands for anything forced induction at Audi. We also overheard a snarky explanation suggesting T stands for “thoopercharged” – a goof on letter choice that raises a good question. Why would Audi choose a supercharger after so many years of turbo experience?
For that we posed the question to the Volkswagen Group’s executive director of engine and powertrain Wolfgang Hatz. As Hatz tells it, the switch was a difficult decision. When the S4 project began, his engineers initially began exploring a V6 application with turbochargers. During development though, one of his team suggested they consider a supercharger, so a second concept began development alongside.
Hatz explained that there are challenges in packaging turbocharger systems with Audi’s current crop of V-configuration engines. These engine packages are short, which invited placing the turbo atop the engine… but this raised fitment issues on the V6, particularly due to the tight constraints for which it was planned. Putting the turbos far away, like behind the engine, makes it harder to achieve ULEV2 emissions and also increases turbo lag.
With two concept engines developed, Hatz says the choice became clear. The German still believes turbos are the go-to tech for super high-performance like the RS 6, but thinks the supercharger setup is better applied to a 300-350 hp program like the S4, as the supercharger benefits from more compact packaging and more immediate torque delivery akin to a V8.
Refinement was another important parameter for the 3.0T. It sees duty in 333-hp guise in the S4 and eventually the S5, but this engine is bound for plenty more Audis as the demand for more fuel-efficient engines rises. A 280-hp version of this mill has already been shown in the facelifted A6, while fitment in the Q5 is planned and we wouldn’t be surprised to see the 3.0T replace the base 3.6 in the Q7 when that model gets a facelift next year.
Given the proliferation of 3.0T-powered models, there was a big push to minimize noise vibration and harshness and make the forced induction virtually invisible. You’ll strain to hear even a hint of supercharger whine under partial throttle at around 2100 rpm, though this will likely be your ear’s only clue. Audi even dipped into its TDI bag-of-tricks to aid in this push for refinement, adding padding to the airbox as it does for diesel models in order to minimize sound. Even the bark of the S4’s engine is only truly appreciated from outside the car. No doubt the aftermarket will come up with solutions for S4 owners seeking proof of performance they can hear.
Audi also touts the engine’s efficiency. In their presentation on site in Mallorca, Audi AG’s product planning staff echoed the sentiment. The new engine is said to use 27% less fuel. Off-the-record early estimates at EPA figures put the car at 17 mpg city / 26 mpg highway for the 6-speed manual transmission car and 17 mpg city / 27 mpg highway for those fitted with Audi’s new 7-speed S-tronic.
Yes, the S4 will come with both a 6-speed manual and Audi’s new 7-speed S-tronic. Those following news of the new S4 and the demise of an Avant version may have feared that Audi would simplify to just one gearbox as well. Fortunately, we get the manual gearbox, and the Tiptronic is replaced by Audi’s latest dual-clutch sequential – a first fitment for the North American market for this longitudinally-mounted 7-speed manumatic.
Audi says the outgoing S4 sold in a 50:50 ratio of manuals to automatics, though expects that to change to 40:60 in favor of S-tronic due to the technical superiority – faster shifts, better fuel economy and equal acceleration performance to the stick.
A new forced-induction engine in the schema of the S4 is a big deal, but even bigger is a fundamental change to Audi’s quattro all-wheel drive system. Yes, the S4 still uses the tried and true 40:60 split Torsen center differential, but Audi introduces a new facet of quattro with the pairing its latest sport differential at the rear.
This evolved setup utilizes a superposition gear on both the left and right sides – connected via a multi-disc clutch that can apportion almost all of the power by an electro-hydraulic actuator to the right or left rear wheel. Action is controlled by computer able to act in under 100 milliseconds.
The main function of the sport differential is to send power to the outer rear wheel in a turn to help stabilize and even throttle-steer the car. Where ESP helps control the car via braking by utilizing sensors for yaw, speed, steering angle, throttle, etc., the sport differential does the same with throttle in an effort to neutralize the effects of understeer. The rear sport differential is optimized to work even when the car is coasting and even when the clutch is engaged. Think of it as the antithesis of ESP.
Cars like the test vehicles we encountered in Mallorca paired the sport differential with the Audi Drive Select (ADS) system. In addition to its three-tiered (Comfort, Auto, Dynamic) settings for steering weight and ratio, throttle, dynamic suspension and shift points in the case of an automatic car, the Sport Differential also gets three levels of tune when paired to ADS.
In Comfort, the Sport Differential is used exclusively for enhanced stability. One way it does this is by eliminating load-reversal upon accelerator lift or quick brake application. In Dynamic, the focus is the car’s agility. Auto mode sees a mix of the two, influenced by the input characteristics of the driver.
Audi of America is still determining how to package the Sport Differential for America. They could make it standard equipment, a stand-alone option or pair it with Audi Drive Select. We’d vote standard equipment, but understand the price competitive pressures placed on the S4. That considered, we’d next vote for the sport differential as a stand-alone option.
Word is the Sport Differential would retail for roughly $900. Paired with the already expensive Audi Drive Select ($2900), that’s just shy of $4,000 more in added cost. Plus, the enthusiast driver who will demand the Sport Differential is also likely to want to install his own suspension from H&R, KW, STaSIS or the like, and these aren’t exactly cohesive with the complex Audi Drive Select system… at least not yet.
Out on the roads of Mallorca, the S4’s increased torque was readily on tap. Inside, the car seems quiet – almost too quiet. The engine note you hear has the bark of the V6 without the more recently familiar wail of the elder S4’s V8. What exhaust note there is comes off as muffled from the inside – perfect for those looking for refinement, though we bet many S4 owners will turn to the aftermarket for audible enhancement and the side benefit of freeing more ponies.
The S4’s Eaton kompressor is barely audible at all – again by design we’re told. A discerning ear will pick up a brief whine just over 2000 rpm and probably off throttle. Audi erred on the side of refinement again, figuring most customers will want it seamlessly indistinguishable, while those who want more probably know who to call to make it bawdier.
Under full acceleration, torque comes on fast. Throttle inputs seem quicker than previous Audis we’ve driven and our Audi Drive Select-fitted car is running in Dynamic mode. Depress the accelerator and you feel the torque build perhaps a bit unnaturally – the only real give-away that it’s a supercharged six if you’re intimate with the power delivery of the 4.2 V8 in the S5.
Though we’re in an all-new car, there’s a lot that feels familiar here. Handling settings seem nearly identical to ADS-fitted S5s we’ve driven – something we confirm with Audi staff later. The ADS-fitted variable ratio and weight steering is also precise, well-weighted and communicative.
Our car sports Audi’s new longitudinal 7-speed S-tronic and it feels more sorted than pre-production units we’ve driven in the past. Standing starts come as seamlessly as a torque-converter Tiptronic, though shifts happen much faster and cog choice is much more intuitive in auto mode. The transmission doesn’t have launch control, but it does vary depending on the setting of the Audi Drive Select System. There’s no Sport selection point on the shift gate, so those looking for spirited handling and dynamics without spastic revving for daily use will want to set up an Individual tailored program in the MMI system.
In roundabouts or tight curves not bordered by stone walls fifteen years older than dirt, we push the S4 hard trying to get a feel for the sport differential. We think we feel the car push into a bit of oversteer as we power through a traffic circle, but we don’t know the roads and we’re on our way to a track so there’s no need to go all Ronin on this little Spanish town.
Shortly thereafter we’re at the Circuito Mallorca. The track is a very small, tight track with a map that looks like a set of tangled iPod earbuds. It is well-suited for fleshing out the handling dynamics of the S4 sans the straights needed for nosebleed speeds. And here’s something interesting – we’re here to test an Audi with the next evolution of quattro and it just started raining.
We take our first few laps of the course with Audi Drive Select in Dynamic and ESP still fully engaged. Learning the course, the added stability of the system is clearly evident. Where we expect the car to chatter its way into ESP-numbed oversteer, the S4 continues to track. Pushing it further, the S4 actually begins to dance.
Hit a corner wrong, with harsher aggressive steering or throttle inputs and the new S4 does what we expect it to do – a willingness to understeer and engage the ESP, sapping speed via the brakes. Then again, it does seem a bit smoother – a bit less likely to fall back on ESP in the first place. A few more laps and we are learning that the S4 is willing to forget about ESP almost entirely and focus on Sport Differential-controlled corrections. Oversteer and throttle-on drifting to a point of opposite correction are both viable… even with ESP still active so long as you’re smooth with your lines and your inputs.
Disengaging ESP, the Sport Differential is still active. Go hot into a corner and turn in – you can feel the trailing throttle begin to slide you around. Stay on the long pedal, correct the steering and she’ll slide out in full four-wheel drift. It’s hard to believe the S4 would be this animated on a dry surface, but the dynamics are still there. Audi claims a 55:45 weight distribution, though the car actually feels more balanced than that.
Where S4s and Audis of old were still enjoyable to toss around in such conditions, the Sport Differential dials it up to virtually full-on hooligan as you might expect in a rear-wheel drive BMW… except there’s a safety net – front wheels pulling you along as well. Sliding around yet another tight corner on the Circuito Mallorca, we’re ready to declare this the best handling Audi ever, second only to the R8. The Sport Differential is a game changer and we can only hope it will proliferate into as many Audi quattro models as possible.
Outside and In
You have to hand it to Audi design, the S-car formula is so defined that you could guess how this car was going to look from the moment you’d seen your first A4 S-line. Elements expected were the S-line body treatment with red S-badges, painted sills, aluminum trim at the front and rear like the S5 and the same grey grille with chrome struts seen on all the other S-models. Standard 18-inch wheels, minimum to fit over the S4’s front brakes, and optional 19s again are straight out of the S-car partsbin. We didn’t foresee the larger trunk lid spoiler, actually a newer more aggressive lid like the one on the B7 RS 4, or the “V6T” badge on the quarter panel – a few unexpected details thrown in for good measure.
The S4 will likely be panned for its subtle exterior design. With the more conservative 18-inch wheel diameter, the car looks a little too run-of-the-mill A4… but then again S4s have always had a sleeper air about them and wheels can be easily changed. Our only real beef is the “V6T badge”. We get the marketing cache of using one letter “T” to denote forced induction, but think it might be lost on the traffic light audience who “ooh” and “aah” over V8 and V10 badges on other S-cars. We’re guessing they also won’t be much impressed by a less exotic V6 setup. Instead, we’d prefer a subtle “Supercharged” badge similar to the rectangular S-line adornments, but these are merely minor complaints. The car itself is understated and handsome – the best of the A4 breed thus far.
Inside, the S-car formula continues. The standard A4 digs get the same upgrades as the S5. This means bespoke instrument cluster, shift knob, accented stitching, the more bolstered sport seat available in contrast leather colors or alcantara and belt line trim in carbon fiber, aluminum, wood or steel weave… just like the S5. It may be formulaic, but all components are so good – so natural feeling in this car that it seems just right and we’d change very little.
During our time in Spain, we had a chance to spend some time in a range of S4 cabins. Our white sedan used for photography had the two-tone leather with a dark brick red-like leather insert, while another Avant tested had all black leather and the Imola Yellow track cars sported the S4 signature leather and alcantara mix in an all-black combination. All were handsome, though the two-tone configuration just doesn’t translate as well in an all-leather pairing… not like the old dark leather with colored alcantaras once offered.
S-tronic cars get the same shifter handle as run-of-the-mill Tiptronic A4s and here’s where we’d dip further into the Audi partsbin if we called the product shots. An alloy knob/lever like that of the TTS would be a welcome change to differentiate this car’s S-tronic configuration. While we’re at it, we’d also retain the shifter’s Sport selection point for shifting into aggressive shift points on the fly. Alas, such a setup won’t happen this time around, and the configuration offered is far from a consolation and we’ll happily suffer in silence all the way to the track.
If it’s forced induction and it’s Audi, you can bet the aftermarket is already chomping at the bit to augment the 3.0T FSI even further. Of course, upgrading a supercharged direct-incjection engine won’t be as easily performed as it was with the the old 2.7-liter biturbo, but players in the aftermarket are still bullish.
Checking in with aftermarket players like APR and VF Engineering, we weren’t surprised to find both forced-induction-focused companies more than interested in the 3.0T FSI. VF’s Nik Saran suspects the natural path in the beginning will be focusing on the duty cycle of the supercharger and fuel system, as well as recalibrating the ECU.
APR president Stephen Hooks got specific in what he expects we’ll see first from the Audi aftermarket. He envisions there will be an initial wave of products that hit the market centering on software upgrades, pulleys, belts, downpipes and exhaust. Hooks estimates these should net horsepower in the low-to-mid 400 range. A larger supercharger would be needed for further power levels and space is already known to be confined. As a result, bulged hoods may become a necessary design cue in staged aftermarket development.
The new S4 will begin sales in Europe as early as Q1 of 2009. Pricing has already been announced at 50,950 Euros for the sedan and 52,600 Euros for the Avant. That’s a welcome 4,500 Euros below the outgoing B7 S4. Asia is next to get the S4, with cars arriving next summer. Finally, North America gets the car in the fall of 2009 with the coming of the 2010 model year.
Given the timing, we expect the new third generation (3G) of MMI to also be fitted, including real-time traffic data in major markets and 3-D building modeling in areas where data is available.
The Sport Differential will be available in the S4 from the outset. As mentioned, Audi product planners are still debating the value of making this piece of kit standard, a stand-alone option or part of a package with Audi Drive Select. Whatever they decide, we’re told you can expect the S5 to also get the same at that time, though the coupe will remain a V8 at least until its scheduled facelift.
One other note, we hear that a power sunroof will be standard. In today’s world of US-specific curtain airbags, the days of cost-effective sunroof-delete options may have gone by the wayside. We’re told there are three roof stampings for the S4 – US sunroof, rest-of-the-world sunroof and rest-of-the-world no sunroof. Like the S4 Avant, demand for a no-sunroof S4 is so low, there just was no business case for developing two American market roof stampings nor was there reason to go no-sunroof on all S4s.
All things considered, the next 10 months until the S4 arrives stateside are going to be long ones indeed. When it does hit dealers, the latest S4 will undoubtedly square off against the likes of the BMW 335i – a natural rival for which it’s well prepared to compete. A more fuel-efficient and tuner-friendly engine in the larger, lighter and more balanced B8 chassis topped off with the new sport differential wild card make for a car that will be the best from-the-factory S4 yet, and one that gives much more weight to the needs of the hooligan.
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