Turbo Magazine

While BMW is considering building convertible M3s, Dr. Jeffery Point showed little patience as he enlisted the help of Race Marque Systems to bring a 328 convertible up to M3 specifications. Race Marque Systems (RMS) is a Van Nuys, California-based company specializing in BMW tuning. In fact, this type of M3 transformation is not a new endeavor fot the talented company. Dr. Point not only wanted the BMW to be taken for an M3 by onlookers, his mission was to fool the experts and most of all be able to run with the big dogs from a performance standpoint.

The heart of any BMW M3 is its hard-charging 3.2 liter in-line six. To put this 328 at the M-Power level RMS stroked the 2.8-liter six to 3.2 liters by swapping to a 3.2 liter crank and shorter rods. The engine features an RMS Super Sport head with port-matched runners, radiused valves and a multi-angle valve job.

Custom RMS cams that were profiled for forced induction were put in charge of the valvetrain.  Yes, this one-off drop-top M3 was conceived as a supercharged beast that would stand alone in a class all its own.  Pressurization is provided by RMS' supercharger package based on a Powerdyne centrifugal blower.  For this application, the supercharger was dialed in to generate seven psi of manifold pressure.  Fuel enrichment was handled with upgraded injectors and an RMS-reprogrammed M3ECU.  RMS swapped the stock 19 lb/hr injectors with 24 lb/hr units.  The M3-spec makeover continued with the  proper wiring harness, mass air sensor and badging. An RMS street-legal T304 stainless-steel header and RMS cat-back exhaust system helps evacuate spent gases.

The rear suspension was converted to M3 standards with M3 trailing arms and the rear disc brakes were upgraded to race-bred M3 binders. Up front RMS' Brembo system with two-piece rotors and hard-biting four-piston calipers. The front suspension's spindles, bearings, and hubs were converted to M3 pieces. The remainder of the suspension was transformed to RMS Stage 2 specifications. Specially-valved Koni struts with adjustable damping are teamed with adjustable sway bars and an upper strut tower brace. The wheels are 17-inch M3 originals which, along with M3 side moldings, really convinces onlookers this is a real M3.

Inside, the transformation continues as savvy BMW enthusiasts will recognize the trip computer and trim items as M3. The gauge cluster leaves no doubts of its origins as its adorned with M3 badging.

The Cabriolet drives home "Ultimate Driving Machine" hype with raw power. Thrust to the tune of 364 dyno-tested rear-wheel horsepower. The M3 six is known for its torque and the supercharged RMS stroker delivers the goods in that category as well. From 3000 rpm to redline there is in excess of 250 lbs-ft of torque poised in the corral. Peak torque checks in a 315 lbs-ft and is realized at 5000 rpm.

To say the RMS transformation is thorough is a drastic understatement as every area that matters or is M3 identifiable has been carefully massaged. It's no surprise BMW is considering building a drop-top M3 of its own.