Shoehorning a proper M engine into the new Z4 seems to be too much of a challenge for BMW M GmbH, which means a Z4 M is off the cards.

The cost of slotting a full-fat M engine into the new BMW Z4 has killed dreams of a followup to the Bangle-designed Z4 M.

Offered as a coupe or hardtop, the original (and only) Z4 M drew on the 3.2-litre inline-six from the E46 M3. Markus Flasch, head of BMW M, says the new model would need to share its engine with the upcoming G20 M3, which would be too expensive.

"We thought about something like [a Z4 M], however the Z4 M40i as we have it currently... has so much performance that it even gets close to an M2," Flasch told Australian media on a phone hookup from Munich.

"The Z4 already is a true M car – very competent, very fast. Putting in the different engine in a small car as the Z4, putting in a bigger engine, means a lot of effort. So far, we have not found a way this project would make sense," he went on.

In M40i guise, the Z4 pumps out 250kW and 500Nm from a 3.0-litre turbocharged inline-six. That puts the 2006 Z4 M in the shade – although it shades the modern car by 2kW in the power stakes, it's down a whopping 135Nm. Thank turbocharging for that.

The new car is pretty handy around the Nurburgring Nordschleife, too, lapping the legendary track three seconds faster than a stock M2.