Vitamin S- A Look at the New Audi S4

Boost. No, it's just not a crappy energy drink or lame synonym for car theft. Boost from a supercharger or turbocharger, paired with smaller displacement engines and often all-wheel drive, is a shared theme in a genre of cars born out of the WRC. There's a generation of kids who grew up on PlayStation rally games, saved up for their first WRX or Evo, and now are ready to take the next step. It is this rally generation — one not unfamiliar with the idea of natural resource conservation or the need to be greener, who should be most interested in the 2010 Audi S4.

Of course, Audi is not new to forced induction or rally racing. It made its modern name in rally and raised the word "quattro" to legendary status. The first S4 was of the breed as well — a 250-hp, twin-turbocharged V-6, all-wheel drive sedan that pre-dated both the Evo and the WRX in the American market.

Most car enthusiasts know where it went from there. Audi dropped the turbo V-6 in favor of a V-8 engine with one more horsepower than its M3 peer's inline six. Boost was blown off, if only for a while.

That brings us to 2008. The BMW M3 has gone V-8 as well, and moved upmarket to duel with the likes of the outgoing Audi RS 4. Meanwhile, that rally generation is graduating from college, making more money, thinking about kids, and looking to trade out of their boy-racer rides. BMW was already in buyers' sights with the turbocharged, all-wheel drive 335xi sedan, but Audi was staying the course with its naturally-aspirated V-8. With the 2010 S4, however, the brand is looking to chase after boost fiends again, this time with a supercharger.

Essentially, Audi has taken a built 3.0-liter version of its direct-injection V-6 and fastened an Eaton four-vane, roots-style supercharger on top. The setup is good for 333 hp and 324 lb-ft from a wide 2900 to 5300 rpm. That's 11 horsepower down from the old V-8 S4, but the power curve tells the story: Torque is up by 12 lb-ft over more revs, dropping the car's official zero-to-62 figure by half a second, to 5.1.

You'll notice a "V6T" callout on the front quarter panel, but that's a little confusing. We hear "T" stands for any forced induction — not just turbos — in Audi-speak. We overheard a snarkier explanation — "T" stands for "thoopercharged," but that's definitely not the official word. It begs the question though — why a kompressor and not a turbo?

To answer that, we hooked up with the VW Group's engine czar Wolfgang Hatz. Hatz says they ran two programs internally — one examining turbo technology, the other examining superchargers. A challenge in design, according to Hatz, is the packaging. Audi's V-package engines are short, so optimum placement for either getup is in the cylinder valley. Placing turbos behind the engine made ULEV2 emissions hard and turbo lag worse, and placement in the S4's crowded engine bay would be tight.

Torque was another factor. It's more immediate with the supercharger, making it feel like a V-8 — which makes sense, as this engine is expected to see duty in the A6, Q5, and Q7 as well. Hatz still believes turbos are the go-to tech for higher-performance models like the RS 6, but thinks the supercharger is better for 300-350 hp applications.

No surprise, this engine is more fuel-efficient than its predecessor. Audi touts 27 percent less consumption and off-the-record early estimates at EPA figures puts the car at 17 mpg city and 26 mpg highway for six-speed manual models, while and 17 mpg city and 27 mpg highway is the unofficial figure for cars fitted with Audi's new seven-speed S-tronic.

Those are the two transmission choices: a six-speed manual and Audi's new seven-speed S-tronic — their name for a dual-clutch transmission. Audi says the outgoing S4 sold in a 50:50 ratio of manuals to automatics, though they expect that to change to 40:60 in favor of S-tronic due to its technical superiority — faster shifts, better fuel economy, and equal acceleration performance to the stick.

All of it sounds good so far, but it'll still need more of a hooligan factor to win over the aging Evo guys. That's where Audi's new rear sport differential comes in. 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 individual wheels, the sport differential does the same with engine torque 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. If it sounds familiar, that's because similar systems are employed under various names by Mitsubishi (the Evo's Super All-Wheel Control) Acura (Super-Handling All-Wheel Drive) and BMW (the X6's Dynamic Performance Control).

The sport differential itself 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 that reacts in under 100 milliseconds.

All of the cars we sampled 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 response, dynamic suspension, and shift points on the automatics, 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 seeks a mix of the two, influenced by the input characteristics of the driver.

It is believed that the sport differential and Audi Drive Select will be offered separately as options when the S4 hits dealers next fall as a 2010 model. Word is the sport differential would retail for around $900, and ADS already sells in the A5, S5, and A4 for $2900.

Inside, the car seems quiet — almost too quiet. The engine note you hear has the bark of a V-6 without the wail of the elder S4's V-8. 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. Likely buyers of this car know the capabilities of the aftermarket and aren't shy about exploiting it.

The S4's supercharger is barely audible — again by design, we're told. There's a brief whine just over 2000 rpm off-throttle. Audi erred on the side of refinement again, figuring most customers will want the blower seamlessly indistinguishable, while those who want more probably know who to call to make it more bawdy.

Under full acceleration, torque comes on fast. Throttle inputs seem quicker than previous Audis we've driven and we've got the ADS system set to "dynamic." Depress the accelerator and the power comes on a bit unnaturally — the only real give-away that it is a supercharged six if you're intimate with the power delivery of the V-8.

Our car sports the new seven-speed S-tronic and it feels more sorted than pre-production units we've driven. 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 how high the engine revs before engaging the clutch, depending on the setting of the Audi Drive Select system. There's no "sport" selection point on the shift gate for ADS cars, so those looking for spirited handling and dynamics without spastic revving for daily use will want to tailor their own settings in the MMI system.

Once free of roundabouts and tight curves bordered by looming stone walls, we push the S4 hard. The steering, variable in both ratio and weight, is precise and communicative. The sport differential pushes the car into a bit of oversteer as we power through a traffic circle, but the roads are unfamiliar and we're on our way to a track. There's no need to go all Ronin in this little Spanish town.

Shortly thereafter we're at the Circuito Mallorca. The track has a very small, tight layout that looks like a set of tangled earbuds in the bottom of your man-purse. It is well suited for fleshing out the handling dynamics of the S4, sans the straights needed for nosebleed speeds. To make things interesting, it's just started raining, which should make the car that much more animated.

The first few laps of the course are taken with Audi Drive Select in "dynamic" and ESP still 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.

Hit a corner wrong, with harsh steering or throttle inputs, and the new Audi does what we expect it to do — understeer and engage the ESP. Then again, it does seem a bit smoother, like it's a bit less willing to fall into the ESP safety net in the first place. A few more laps and we are learning that the S4 is willing to forget about the nets almost entirely and focus on differential-controlled corrections. Some throttle-on oversteer is 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. Keep your boot in it, correct the steering and the S4 will slide out in a full four-wheel drift. It's hard to believe the S4 would be this cheeky 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 mildly enjoyable to toss around in such conditions, the sport differential makes this one seriously entertaining. Sliding around yet another tight corner on the Circuito Mallorca, we're ready to declare this the second best-handling Audi ever behind the R8. The sport differential is a game changer for Audi, and we can only hope it will proliferate into as many of their cars as possible.

Exterior differences from the A4 are formulaic given Audi's consistent design language. New elements are almost identical to the S5's changes — S-line body treatment with red S4 badges, painted sills, aluminum trim at the front and rear and the same grey grille with chrome uprights. Standard 18-inch wheels, minimum to fit over the S4's front brakes, and optional 19s again are straight out of the S-car parts bin. The only design wildcards here are a larger spoilered trunk lid and the "V6T" badge on the quarter panel that kind of loses some cachet in translation, especially when parked next to a V-8 or V-10 on an Audi lot.

Inside, the S-car formula continues with more bits seen first in the S5. This means a different instrument cluster, shift knob, accented stitching, and bolstered sport seats available in contrast leather colors or Alcantara. As with the coupe, beltline trim comes in carbon fiber, aluminum, wood, or steel weave. It's a top-notch formula, but formulaic nonetheless.

A quick call to a couple of tuners after we returned gave us a little bit of insight on tuning potential for the motor. Alabama's APR Tuned got the most specific, speculating on what we might see for the car. They envision there will be an initial wave of products that hits the market centering on software upgrades, pulleys, belts, downpipes, and exhausts. President Stephen Hooks estimates these should net horsepower in the low-to-mid 400 range. A larger supercharger would be needed to raise the power further, and space is already at a premium. As a result, bulged hoods may become a necessary design cue in staged aftermarket development of the S4.

The new S4 will begin sales in Europe as early as Q1 of 2009. Pricing has already been announced at €50,950 for the sedan and €52,600 for the Avant. That's a welcome €4500 below the outgoing B7 S4, and we hope the newfound economy will carry over to the States.

Will Generation Rally accept the S4 as a stepping stone from an Evo or the like? We suspect it will. The S4 lacks the raw edginess of those turbo toyboxes, but most of us start to grow out of stark interiors and buckboard rides as our hairline recedes and our 401K grows. When they're ready for the move, the Audi S4 — with its all-wheel drive, forced induction and refined hooligan nature — should be a familiar configuration with a lot more luxury and refinement.