Elevating Bavaria's ultimate driving machines to the next level of performance and style is daily business for Italy-based Racing Dynamics, which works its mercurial magic on the full BMW line from the lowliest 3-Series to the grandest 8-Series. In Europe, the company is a respected tuner, assembling complete packages on new BMWs, but in the U.S., its business has been as a dealer and mail-order supplier of parts-until now.
Racing Dynamics is moving aggressively in a new direction, looking to establish a facility in California to build modified engines and complete cars for American consumption. To showcase its high-quality conversions, Racing Dynamics delivered to Motor Trend a sinister-black K30.4 Cabrio demonstrator featuring the full catalog of modifications.
The heart of the performance gains comes from a 3.0-liter DOHC inline-six engine conversion, which can be purchased singularly for $5800. Displacement of a 3-Series' stock 2.5-liter engine is enlarged by increasing both bore and stroke, resulting in a boost from the stock 189 horsepower to 255 at 6000 rpm. The requisite machining work combines with the new Mahle pistons, special connecting rods, longer-duration camshafts, a stainless steel exhaust manifold, a hi-po catalytic converter, and a twin-tip muffler to produce a silky powerplant with significantly more initial grunt than the original 2.5-liter, plus the heart-pounding rush of an M3-like top-end charge. In a straight-line blast to 60 mph, the K30.4 Cabrio arrives in 6.0 seconds; the stock M3 trails by 0.2 second.
As soon as the fluorescent tach needle passes four grand, the power surges with a tidal force of acceleration that can hurl the Cabrio past more-plebeian Bimmers like a cannonball.
The ride height is lowered via sport coil springs and Bilstein gas shocks, while the remaining chassis components are fortified with adjustable front and rear anti-roll bars, and urethane bushings. Once caster and camber have been adjusted, the carefully orchestrated combination provides predictably neutral handling, with measured performance on a par with that of the stock M3 coupe. (The K30.4 is only 0.1 second faster in our 600-foot slalom.) While broken pavement is quick to remind of the stiffened ride and ultra-low-profile 18-inch tires, the ride compliance is admirable considering the car's ability to navigate corners as if it were tethered to a pole by a carbon-fiber lanyard.
The greatest area of compromise in this topless sled is the brakes, which provide daylong fade-free stopping, but at the expense of gravelly, attention-gathering noise. The factory BMW M3 stops a shopping-cart-length shorter from 60 mph (117 feet versus 121), but at higher speeds, the K30.4's Brembo four-piston calipers grip the cross-drilled discs with such force as to strain the seatbelt anchors.
Racing Dynamics tastefully outfitted the convertible with a full polyurethane body kit, including front fascia, side skirts, and rear valance, but the subtle close-to-factory exterior treatment understates the bravado felt by any driver with a pulse. On the styling down side, the diminutive sport mirrors look sleek, but are as functional as holding a makeup compact mirror out the side window. Racing Dynamics' trademark five-spoke wheels (18x8.0 inch) are wrapped with Pirelli P-Zero Asimmetrico tires (235/40ZR18 front, 255/35ZR18 rear).
Inside, the driver is treated to a well-contoured, airbag-equipped, green-stitched Racing Dynamics steering wheel, logo-adorned floor mats, stainless steel door sills, a burled-elm shift knob, a perfectly angled dead pedal, a production-number plaque, and a special instrument cluster with fluorescent needles. Numerous logo-emblazoned reminders are sprinkled throughout, leaving no question as to this car's unique origins.