If a vehicle like the BMW 3 Series sedan is the Ultimate Driving Machine, what does that make the 2006 Z4 M Roadster, the latest Bimmer that made its debut at the 2006 North American International Auto Show in Detroit? Call it the Super Ultimate Driving Machine or the Ultimatest Driving Machine – frankly, this promises to be one sweet ride that should be bestowed with whatever positive terms you can think of.

Arriving this spring, the 2006 BMW Z4 M Roadster will sticker for $51,995, including destination charges. The M’s launch coincides with the release of the updated 2006 Z4, a model that will sell for $36,295 with a 3.0i badge and $42,795 with a 3.0si moniker.

But back to the shining star of the Z4 family, the M Roadster. Under the hood is a 3.2-liter, inline six-cylinder engine pushing a healthy 330 horsepower, propelling this drop-top to 60 mph in less than five seconds and hitting an electronically-governed 155 mph. If you ride with the top down, you may want to staple your hat to your head at those speeds. The standard transmission is a six-speed manual, though a six-speed Steptronic automatic with paddle shifters will be available.

Behind the scenes, the 2006 BMW Z4 M Roadster plays host to a good deal of technology that works to keep all 330 horses in check. A floating compound performance brake system, like that included in the M3’s Competition Package, provides excellent stopping power. Playing supporting roles are other systems designed to bring things to a quick and safe halt, like Brake Drying, Brake Standby, and Brake Fade Compensation, while Start-Off Assistant holds the M Roadster still when the brakes are released on an incline.

More noticeable are the slight changes on the 2006 Z4’s exterior. The headlights, which now house xenon bulbs, are part of a revised front fascia that features different fog lights, and the tail includes two-stage adaptive brake lights.

Photo by Ron Perry