A nice idea but given the weight of the engine it was destined to remain a one-off.
The BMW Z3 offered an array of four- and six-cylinder engines, but the M division has revealed a unique prototype from deep inside its skunkworks packing a V12. Few details were released along with this trio of never-before-seen photos, but given the time period in which the Z3 was built, we'd surmise it packs the 5.4-liter V12 from the 750i and 850Ci, or even the larger 5.6 from the 850CSi (which was, in all but name, essentially an M8), but probably not the 6.1-liter unit BMW made for the McLaren F1.
With 322 horsepower, the 5.4 would hardly have been worth the packaging and weight issues over the 315hp 3.2-liter six from the Z3 M. The 375hp V12 from the 850CSi might have been more worthwhile, but the 70 percent weight distribution over the front wheels would have made the prototype practically undriveable. "We don't know why a V12 engine was built into a BMW Z3 years ago," admitted the Bavarian automaker. For our part, we don't really care why it was built. We're just glad to know it was, because if there's one thing the world needs more of, it's V12 roadsters.