BMW has confirmed that a rear-wheel drive roadster powered by a new generation 3.0-litre inline six-cylinder turbo-petrol engine rather than a hybrid drivetrain will be the first fruit of its sports car development deal with Toyota.
The replacement for the Z4, which is being developed in concert with Toyota's take on a new generation Supra, is expected to go on-sale by late 2017.
But the engine, which is the largest member of the new BMW modular engine family that also includes 1.5-litre triples and 2.0-litre four-cylinders, will debut in the G11 and G12 generation standard and long wheelbase 7 Series saloons in 2015.
Coded B58, the sophisticated 3.0-litre direct injection turbo-petrol engine is expected to produce around 250kW and 440Nm in the 7 Series, which bodes well for strong performance in the roadster, reputedly set a sub-1400kg kerb weight target.
"The first car you will see on this platform of the sports car will be a classic six-cylinder BMW," senior BMW product spokesman Kai Lichte told motoring.com.au at last week's 2 series Active Tourer launch in Austria.
But Lichte refused to be drawn on reports that future BMW versions of the sports car would follow Toyota's expected lead and employ a hybrid drivetrain, potentially all-wheel drive and featuring super-capacitors rather than battery packs to store and discharge electrical energy.
"That's too early to talk about this," he said.
"First of all we will have the six-cylinder engine that's for sure. Everything else will be – might be – later. But it's really too early [to discuss]."
The Z4 replacement's debut with six-cylinder engine debunks reports the car would launch with 2.0-litre turbo-petrol power, although that will surely come down the track.
Lichte said the co-operation with a partner such as Toyota was essential if BMW was to produce a successor to the Z4 (pictured), which provided strong emotional rewards for the company but not profits.
"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."
BMW's particular responsibilities within the sports car project including the development of orthodox petrol engines and light-weight materials, the latter making particular sense in the wake of the ground-breaking work done on the i3 and i8.
Within the wider technical collaboration announced in 2011, BMW is also the lead partner on light-weight construction and combustion engines including diesel. Toyota has the lead on hybrid and fuel cell technologies.