All the tuning potential of the Audi TT 225 without the image, an Audi S3 makes a lot of sense to tune..
1. WHEELS AND TYRES
The standard wheels are heavy and pretty uninspiring looking, so a replacement set should be high on your list of priorities. 8x18in wheels are generally the way to go, usually with 225/40×18 tyres, as unfortunately much wider usually gives clearance issues. With the correct choice of tyres grip should still be ample thanks to the great Quattro 4WD system.
Although the standard brakes are fairly substantial, the car is heavy and prone to brake fade when used hard on track. A simple track pad upgrade can help, but for real performance increases a big brake kit is the only viable option. There are various big brake conversions available, and if you want to go OEM+ style, there are kits to enable big brakes from the hot Audi RS models to fit the S3.
The suspension is quite soft as standard, so the immediate port of call is a decent set of coilovers. Beyond that, uprated anti-roll bars are widely available and can help reduce body roll without rock solid suspension, and getting the geometry set and the car corner weighted can have a bigger effect than actually changing components.
Although we wouldn’t recommend drastically changing the S3’s looks, a few well thought out changes are never a bad thing. A spot of de-chroming, an enlarged front bumper opening for a big intercooler, and a front splitter can work wonders for the exterior. For big power engines a vented bonnet is also a good idea to help keep under bonnet temperatures at sensible levels.
The engine is the 222bhp version of the VAG 1.8T lump, and therefore pretty damn tuneable. A decent front mount intercooler, turbo-back exhaust, induction kit, and remapped ECU is a great first stage and can give it around 275bhp and over 300 lb/ft torque. Beyond that it is bigger turbo time, but along with uprated pistons, rods, fuel system, and so on, even upwards of 500bhp is quite achievable.