On the "show" side of the equation, both vehicles can benefit from downforce producing aero bits that are easily exchanged between both the coupe and ragtop. Subtle details, like the replacement of the standard side turn signal units with custom AC components go a long way to show how much the uber-tuner is obsessed with minutiae.
When it comes to the "go" aspects of performance, AC rarely disappoints and in this case it seems that no stone was left unturned. The rear axle ratio was changed to elicit more lively acceleration, along with a tuned exhaust that provides a few more ponies and a sonorous howl. Different exhaust components are fitted dependent on whether the Z4 is the base 3-liter model or the M-olested version, equipped with the 3.2-liter inline six.
In an effort to strike a balance between power and handling, the ACS4 models are equipped with any combination of tire, wheel and suspension components, of which we lost track of after about 30. Naturally, the disc brakes are upgraded in size, along with new calipers and grittier pads.
Inside, drivers can opt for a custom, airbag equipped wheel, as well as metal pedal sets, shift knobs, handbrake handles and a number of trim materials.
A full break down of the aero components can be viewed, along with a host of photos, at World Car Fans.
[Source: World Car Fans]