It is an open secret that the new Toyota Supra shares its platform and powertrain with the latest BMW Z4. But the Japanese car is a coupe, whereas the German is a roadster.

And according to Toyota, its exterior shares only three pairs of items with the Z4 - windscreen wipers, door mirrors and door handles.

The Supra, code-named A90, is still a camouflaged prototype at this stage, about four months away from its official debut, while the BMW Z4 has already been revealed.

Despite the camouflage applied to the bodywork of the prototype, I could discern the car's shape. It appears to have curves in the right places, including a "double-bubble" on the roof and a protruding "duck-tail" behind the trailing edge of the rear windscreen.

The slinky tail-lights and "ice cube" headlights look nice and the twin exhaust tailpipes are of an appropriate size for a high-performance car. Those pipes produce a delectable burble as I drive off - and straight into downtown Madrid's Monday morning rush hour.

The engine is just a little louder than the exhaust note at these low speeds of 20kmh to 40kmh, limited by the heavy traffic.

Visibility from behind the wheel is superb for such a low-slung coupe. The car is also easy to position on the road and manoeuvre amid other vehicles.

Much of the interior has been shrouded for this media test-drive. Only the driving-related controls and instruments are exposed.

The gear lever and its surrounding switches look like BMW parts, as do the electrical adjusters for the driver's seat. The seat itself supports the torso and shoulders better than the thighs, but offers good overall comfort during cruising.

The Supra's instrument cluster integrates a digital display with physical rev-counter numerals. I have never seen a similar cluster design in any other cockpit before.

And I have never heard as much road noise inside a Toyota before. Not even in the boisterous 86.

Once the engine is racing, and adding its racy sound to the proceedings, intense mechanical music overpowers the road noise.

With its eight-speed automatic transmission left to its own devices in D mode, upshifts are slick but not particularly quick.

The powertrain picks up the tempo dramatically when Sport mode is activated.

Downshifting becomes aggressive and every full-throttle upshift bangs the gear in and plants a big smile on my face - fast.

My smile gets bigger when I play with the plasticky paddles and realise that the gearbox lets each gear cling to the 7,000rpm rev limit (the redline is marked 500rpm below that).

The engine screams enthusiastically like a race-track refugee until I tap the "plus" paddle and do it all over again, just for fun. Rushing the Supra to 100kmh from a rolling start of about 10kmh feels super, and pushing on from 100kmh to 200kmh feels equally super.

The brakes perform fantastically and the brake pedal modulates stopping power perfectly - whether slowing the car down to a smooth stop in the city or scrubbing off speed in urgent chunks on a circuit.

A few laps on the Jarama racetrack reinforce my impression of the Supra's rigid body, vigorous performance, balanced handling, and accurate and well-weighted steering.

Toyota has not provided the car's technical data, but the engine is probably a BMW-supplied, turbocharged 3-litre inline-six that produces more than 300hp and well over 400Nm. The car is said to weigh around 1,500kg.

Supra assistant chief engineer Masayuki Kai says the prototype's hardware is 95 per cent done, while its software is less than 90 per cent finalised.

Hopefully, it drives even better when it is unmasked. The car is expected to reach Singapore by the third quarter of next year.

•The writer is the editor of Torque, a motoring monthly published by SPH Magazines.