The 1.8T powerplant will go down as the most readily tunable VW engine since the air-cooled Beetle's good old 1600cc boxer. Hugely significant gains could be made with only improved airflow and revised engine management parameters, often executed on a completely stock bottom end. The 1.8T was, and is, the epitome of efficiency, functionality and potential.
If you're considering a turbocharged VAG car with a view to increasing its power output by, say, half again or more, the 1.8T is likely your best bet. The reasons are twofold: first, the 2.0T (scion of the 1.8) is still fairly difficult to modify, given its FSI direct-injection technology and one-piece turbo/exhaust manifold assembly. And second, all the parts you'll need for any given power level or chassis adjustment for a 1.8T model are readily available from a number of sources.
A good case for this is the Stasis A4. The 1.8T-equipped B6 has been around for about a year and a half, and is a near mirror image of its sister car, assembled by Stasis for the Sports Car Revolution show aired on Speed TV. Stasis claims that many of the modifications can also be adapted to the B5 S4 and B6 A4.
Powerplant aside, most critical to this project is the chassis and suspension setup. According to Stasis, all added components--springs, dampers, brakes, differentials, anti-roll bars--are designed to be interdependent. When put together properly, they work together to provide maximum performance at an OEM level of comfort. Stasis' aim is to design a holistic package for all driving conditions, from hot laps at the track to the ordinary day-to-day street driveability you'd expect from a premium-level sedan. This philosophy treats the car properly as a system of parts--which any car definitely is--rather than focusing on one or two areas of mechanical performance and throwing off the vehicle's inherent balance.
Suspension mods consist of Hyperco linear-rate coil springs wound on Ohlins double-adjustable dampers (with remote reservoirs up front) and single-adjustable dampers in the rear. The springs and dampers are coupled with a stock anti-roll bar in front and a new, hollow bar in the rear. On this particular car, the spring rates were kept in the middle of the rigidity spectrum (700 lb/in. front, 1000 lb/in. rear) to keep things relatively civil on the street while still offering improved performance for more spirited driving sessions. The hydraulic, nitrogen-charged Ohlins dampers are rebound- and compression-adjustable to fine-tune ride quality and steering response. The whole system rolls on new, 8x18-inch Work Emotion CR wheels wrapped in Conti SportContact 2 tires.
The brakes are something else. We've seen them installed on a few other cars and have become infatuated. The system uses Goodridge braided stainless steel lines and Alcon hardware. The front assemblies are comprised of four-piston monoblock calipers and 14-inch full floating discs. Friction is provided by SBS carbon-ceramic pads. The rear brakes run two-piece 12-inch rotors, stock calipers and Ferodo DS2500 pads.
Naturally, the engine has been worked over, running a Stasis `Stage III-plus' turbo upgrade which pushes this 1.8T into the 300-hp realm. The upgrade includes a cast Inconel manifold, Garrett GT28 turbocharger, a front-mount intercooler and supporting hardware including new fuel injectors. This equipment is enhanced with the appropriate Stasis engine management software and a new high-flow cat-back exhaust to reduce backpressure and enhance boost response.
Modifications along the driveline also include new center and rear differentials. The center diff is a Torsen (torque-sensing) unit that directs torque to either the front or rear depending on where it's needed. Diving into a corner hard on the brakes will yield more power directed to the front. Coming out, hard on the accelerator, the balance will shift to the rear wheels via the Torsen diff and a new limited-slip diff on the rear axle. You've got a pretty competitive sport sedan you can drive to the track.
Stasis treatments are available individually, but the sweet deal is the complete package. A Track Sport package is also available for less money, but this car wears Stasis' A4 Motor Sport package, the top level offering which nets the Ohlins suspension, turbo upgrade and limited-slip rear diff.
And late-model 2.0T enthusiasts fear not. The company has launched a `Signature Series' line of tuning options for the late-model Audi A4, as well as the A3. Two trim levels are available. The Touring Series program provides a more sporting platform with additional power, increased suspension spring rates and digressive damper valving, 19-inch forged wheels and bigger brake rotors. The Challenge Series takes things a few steps further, integrating the above modifications as well as a DTM-inspired aero kit, a high-bias Torsen center differential, a bit more engine power and torque, and a new braking system similar to that on this red car. The package price, rolled into the car's dealer MSRP and starting a shade over $35,000 for a Touring Series 2.0T, offers one hell of a good deal and comes far cheaper than purchasing the upgrades individually. Better yet, these kits are covered by a four-year/50,000-mile warranty, seamless with Audi OEM coverage. That's something you won't see a lot of aftermarket outfits offer.
2005 AUDI A4 1.8T
Longitudinal front engine, all-wheel drive
1.8-liter in-line four, dohc, five valves per cylinder, turbocharged and intercooled, Stasis `Stage III+' turbo kit, software, high-flow exhaust
Six-speed manual, Stasis high-bias Torsen center diff, Stasis clutch-type limited-slip diff
Hyperco springs, Ohlins adjustable dampers, H-sport rear anti-roll bar
Alcon four-piston monoblock calipers, 14-inch floating rotors, SBS carbon-ceramic pads (f), 12-inch rotors, Ferodo pads (r), Goodridge braided lines
Wheels and Tires
Work Emotion CR, 8x18 Continental SportContact 2, 235/40
Peak Power: 300 bhp (est.)