Earlier this week, three images of a V-12–powered Z3 roadster prototype appeared on BMW M’s Facebook page. We’re reasonably familiar with many of BMW’s stillborn projects, but this is the first we’ve seen of a 12-cylinder Z3. BMW tells us that the Frankenstein Z3′s origins and whereabouts are “a bit of a mystery.”

BMW told us that the company tries to design its vehicles with enough room and commonality so as not to limit future powertrain options. Thus, such swaps are theoretically possible; it’s configuring the ancillary hardware that generally poses a problem. The Bavarians would not comment on which 12-cylinder was used in this prototype, though we think the powerplant in question likely is the 5.4-liter M73. The M73 saw duty in the 7- and 8-series during the late ’90s and early 2000s, making 322 hp. For comparison’s sake, the Z3-based M Roadster used the S52 3.2-liter inline-six from 1998–2000, making 240 hp, while the 2001 and 2002 models were upgraded to the 315-hp S54 of the same configuration and displacement. That’s a lot of extra weight for an extra seven hp, but cool is immeasurable.

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If nothing else, the photos illustrate that even tightly wound German engineers occasionally succumb to primordial Carroll Shelby–tinged urges like the rest of us.

By Andrew Wendler