BMW fans will have Toyota's next Supra to thank for the third-generation Z4, which will arrive as a conventional rear-drive, turbocharged roadster before morphing into a hybrid.
The next Z4 is a car BMW admits would never have happened if hybrid partner, Toyota, hadn't suggested let slip that it wanted to build a belated replacement for its ultra-masculine Supra.
Itself a nameplate closely linked with in-line six-cylinder power, the Supra was discontinued by Toyota in 2002 even though The Fast And The Furious made it famous, but will return in 2017 - just in time for the next Z4.
BMW product spokesman Kai Lichte last week admitted that tying up with Toyota was essential to replace a car that was much-loved at BMW but was not profitable in its second generation.
“The idea is to share the architecture to make cars - some sports cars - more profitable and even to make it work.
“The Z4 roadster segment is declining, so if you want to have a BMW roadster also in the future we have to look at which platform can it be and the economies of scale,
“The segment is declining but we would like to see a car like this because it is close to BMW.”
While both the Supra and the Z4 will eventually be pushed out as hybrid sports cars, the Z4, at least, will arrive powered by the upcoming 3.0-litre, in-line six-cylinder petrol motor, code named B58.
Scheduled to debut in the next-generation 2015 G11 (short wheelbase) and G12 (long wheelbase) 7-Series limousines, the engine will be the biggest development yet of BMW’s one-cylinder, 500cc modular concept.
Already seen in three- and four-cylinder variants with both MINI and BMW, the modular concept will reach out to at least 250 kW of power (up from 225 kW) and around 450 Nm of torque in the stretch to six cylinders. It will mate a more advanced turbocharging system with state-of-the-art direct injection bolted to an all-alloy block.
Current thinking at BMW is to abandon the current Z4’s folding metal roof in favour of a return to a cloth roof. The move to a folding roof added weight, raised the car’s centre of gravity and meant the sports roadster lost a lot of its original owner base.
The new version will return to a kerb weight beneath 1400 kg, which promises athletic performance with the all-new engine sitting behind the front axle line.
Sources at BMW have confirmed the Z4 will benefit from its i3 and i8 adventures in light-weight technology, particularly some of the braver and more idiosyncratic uses of different lengths (and even off-cuts) of carbon-fibre to create specialist strength at light weights.
While a 2.0-litre, four-cylinder engine is certain to be added to the Z4 within a year of its debut, speculation is also rife that it will also add a hybrid model.
Benefiting from Toyota’s Le Mans experience, the Z4 hybrid could use complicated super capacitors to more efficiently gather and spend electricity rather than heavy battery packs. It could also use an electric motor to power the front wheels, making it effectively an all-wheel drive, and could even be moved across to the M brand.
Toyota’s Supra will use BMW’s six-cylinder engine and the chassis has been jointly developed.
BMW and Toyota began collaborating on a technical partnership in 2011, with BMW taking the engineering lead on combustion engines and weight-savings and Toyota leveraging its hybrid and alternative-energy expertise.