The new car, dubbed the Z4 sDrive35is (snappy, we know), will take the Z4 close to M-car territory, with power and torque jumping by more than 10 per cent. That gives the hottest Z4 a peak power output of 330bhp at 5900rpm, while torque jumps to 332lb ft from 295lb ft.
There is also an electronically controlled overboost facility that releases 369lb ft for short bursts under full acceleration.
The new power and torque comes courtesy of a high-flow air intake and increased boost pressure for the twin-turbo straight-six motor.
That's good enough, says BMW, to get the hottest Z4 to 62mph in less than 5.0secs (the current sDrive35i takes 5.2secs to do the same) on the way to an electronically limited 155mph top speed. BMW claims that the engine's efficiency is unchanged, so the 30mpg combined fuel consumption figure should remain.
The sDrive35is also gets 10mm lower M sport suspension, reprogrammed electric power steering and a standard 7-speed dual-clutch transmission.