If there was ever an engine that got the tuning world's attention, it was the 1.8T found in a plethora of vehicles including the Volkswagen Golf, Jetta, New Beetle and Passat plus the Audi A4 and TT. From '96-05 these models sported the K03 turbocharged and intercooled 20v inline-four. It didn't get off to a potent start, however, since early versions developed only 150hp (about 130hp at the wheels on FWD cars). But the engineers knew the motor's potential and released the 225hp Audi TT in '01 using a K04 turbo. The following year, all 1.8T outputs were increased, thanks to a modified K03 turbo. The Passat saw 170hp, while the A4, Golf, Jetta and Beetle enjoyed 180hp, which commonly relates to about 145 and 155whp, respectively.
Since the quantity of 1.8T tuners is more than double any of our previous tuning guides (E36 M3, VR6 12v, E36 325i/328i), we've approached this guide differently - looking at each company's options, rather than price categories. If you're in the market for a 1.8T or already drive an unmolested example, this list should keep you busy for hours.
While numbers will vary from tuner to tuner, and from dyno to dyno, power output for cars with the stock turbo, upgraded software and a cold-air intake (CAI) will usually be between 175-185whp (more with a cat-back or turbo-back exhaust). Once you start getting into K04 turbo territory, don't be surprised to see over 200whp with a good exhaust system. If your pockets are deep, some companies have more radical setups exceeding 300whp...
034 Motorsport
510/657-6707
www.034motorsport.com
One of the major restrictions in the factory exhaust is the downpipe off the turbo housing the cat. So 034 fabricate its own mandrel-bent piece with a bung for the 02 sensor. The $155 piece is reportedly good for an extra 10whp on stock cars, and up to 30whp on modified ones. 034 also fabricate a $850 transverse header for anybody wanting to regulate boost with an external wastegate.
The company is also known for its programmable stand-alone engine management. The 034 EFI will work on any 1.8T engine, and is supplied with a plug-in harness. The EFI features closed-loop boost control, anti-lag, wideband integration, and is designed for DIY tuning. The entry level 1C system starts at under $2000. 034 Motorsport also distributes ATP turbo kits.
Advanced Engine Management
310/484-2322
www.aempower.com
AEM has a CAI for '00-06 Golf/Jetta for $300, and a $507 turbo exhaust manifold.
Advanced Tuning Products
510/445-1682
www.atpturbo.com
Known for its turbo kits, ATP sells a CAI for $119, and a $395 cast-iron exhaust manifold with an external wastegate flange for T25, T3 or T3/T4 turbos. Its front-mount intercooler (FMIC) for Golf/Jetta retails for $975.
Its quick-spooling K03/K04 Eliminator kit for FWD 1.8Ts uses a GT25R for $1750 and gets around 215whp. Next is the G2X kit for the '07 A4 and Passat costing $1275 with installation. By using its software and injectors ($795) and optional 2.75" inlet pipe ($150), it's good for 218whp with 248 lb/ft through the stock exhaust, and 235whp, 264 lb/ft with a 3" test pipe replacing the cat on 93-octane. Torque peaks at 3500rpm in both cases.
The GTRS turbo upgrade uses a GT28RS ball-bearing turbo, which starts at $1595 with installation hardware. If used with ATP's larger inlet pipe, you get 235whp with 244 lb/ft at 4800rpm through the stock exhaust on 93-octane. Add the $780 software and injector upgrade and power surpasses 250whp. Add a 3" test pipe and the number improves to 260whp with 280 lb/ft at 4300rpm. Around 300whp is possible with a full exhaust.
For $100 extra you can upgrade to the GT2871R. With a 3" exhaust and inlet pipe, power can exceed 350whp through the stock intercooler.
Lastly, a stage 4 turbo for '00-02 GTI and Jetta uses a Garrett GT30R dual ball-bearing turbo and includes hardware, external wastegate, GReddy boost controller, injectors, downpipe and exhaust manifold for $4000, giving a safe 300whp.