How to Make a 2003 Z


1. Install a performance exhaust system. The Z4's exhaust is relatively restrictive and the motor can benefit from a larger diameter exhaust system that will help the motor breath better. The installation of a performance exhaust on a Z4 is a pretty involved process and should be handled by a shop experienced with modifying BMWs.
2. Have the engine's electronics reprogrammed. In stock form, the Z4's electronics are pretty conservative. A reprogrammed ECU (engine control unit) will deliver more fuel, spark and air to the motor and will help it make more power and the car itself faster. While this can be done by a professional shop, there are products available that allow you to simply plug into the existing electronics and reprogram them for more power.
3. Supercharge the engine. A common method to getting more power from a Z4 is to supercharge the engine, which is a form of forced induction that forces more air into the motor for a power increase. Supercharging is generally cheaper and more simple than turbocharging (the other form of forced induction). A supercharger kit needs to be installed and tuned by a shop that specializes in performing this type of work on BMWs in order for it to function properly and not damage the motor.
4. Improve the handling and braking. Making your Z4 faster does not just mean simply adding more horsepower to it but also includes improving the rest of its performance so it can go around corners faster and stop faster as well. Remove the stock suspension and install lower, stiffer springs which will reduce body roll and increase cornering speeds. Add adjustable performance shocks to the equation and you will be able to dial in your Z4's handling just the way you want it. On the stopping end of things, install more aggressive brake pads for better braking, cross-drilled rotors for better heat dissipation and braided steel brake lines for more responsive brakes.
5. Replace the stock wheels and tires with a performance wheel and tire package. The Z4's stock tires leave a little to be desired (or a lot if it's using run-flat tires) so installing stickier tires will allow the car to corner faster. Combine the performance tires with lighter performance alloy wheels for even more performance.