You move eastbound on Interstate 195 into the deepening purple haze of the South Florida dusk. Training your roundel on a shimmering Miami Beach skyline, you downshift to third gear and dump the throttle. The tach needle whips around 6500 rpm; an unrestricted, free-flow exhaust roars obscenely as a thrumming mechanical whirr uncoils from the engine bay like a striking snake. Shift up, watch the needle whip past 7500 this time. You lift, skipping fifth to ease it into sixth, and the whirlwind of sound and acceleration abruptly dissipates as though it never happened.

Without warning a pair of triangular HIDs dives into view over your left shoulder, closing rapidly. In the mirror you glimpse a low, wedge-like shape advancing on your flank like some blood-crazed predator. The failing light flashes off a metallic neon sheen.

No worries. You're behind the wheel of Active Autowerke's supercharged M3 prototype. You blip the throttle, knock it back to fourth, and get back on the floor. Turns out you were in the mood for a little Italian.

Force-fed Active Autowerke BMWs have been prowling the streets of Miami and hunting the indigenous exotics since company founders Karl and Mike Hugh began officially turning wrenches under the Active name back in 1981. It's been nearly 30 years, but the dedication to ultimate BMW performance remains.

This, the company's new-generation supercharger kit for the E90-series M3, is still in its prototype stage, meaning it's so far the only one of its kind currently installed on a running vehicle. Everything you see under the hood here is basically a hand-fabricated one-off. Don't expect the end product to be so Mad Max in its presentation; the production version will be visually much closer to something you might see come from the factory.

It's formed around a custom HKS GTS8550 blower developed to Active Autowerke spec. In fact, the compressor remains pretty much a prototype in and of itself. (One other identical unit does exist and currently resides in an undisclosed location.) Having traditionally employed hardware sourced from Europe, Active looked further east for this latest go-around. The decision was a matter of volume, sourcing a larger capacity blower that would work with the confines of the engine bay.

"There were limitations as far as spinning the revolutions to get the airflow we needed to make the power we wanted from the V8," says Karl. "We needed something with more headroom." HKS out of Fujinomiya, Japan, answered the call with a supercharger that met requirements for output and efficiency as well as reliability. Active has successfully tested a similar blower on another shop car for more than 20,000 miles.

The E9X supercharger kit is for all intents and purposes 99 percent complete in terms of operation and performance. Mass producing and packaging the final production parts is next, in anticipation of an official release nearer this October. The complete kit will be all-encompassing: compressor and self-contained oiling system, belt tensioners, plumbing, an integrated airbox for the filter element, fuel enrichment parameters including high-volume pump and injectors, intercooler, provisions for relocating the oil cooler.

Because of the heat soak involved with boosting the S65 V8, running the blower without provisions for an intercooler was not an option. They chose a front-mount air-to-air unit for maximum airflow to both the I/C and the radiator. "The intercooler is capable of supporting 850 hp. Overkill," Hugh says. "But that's good; we can pull back-to-back dyno runs without any heat soak issues. High efficiency, zero maintenance... a win-win for us." Reportedly it all fits with only minor trimming of the front bumper and radiator supports.

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