Gone are the sequential turbochargers (one force-feeding the other) that gave the RX-7 its light-switch power delivery. Banished is the rock-hard ride, along with mendacious chassis feedback that told you how brilliantly everything was going, just before spinning you like a pole dancer into the scenery.

Next April's RX-8 is a road-going version of what we've been teased with over the last seven years at the Tokyo Motor Show. Sadly the razor-sharp lines of the 1995 RX-01 concept and 1999 RX-Evolve have lost their radical edge. The RX-8 is altogether calmer, with a boot from a conventional saloon and a much thinner plan view. Inside, the concept cars' gorgeous, figure-hugging, soft-leather seats have been widened and hardened for hamburger-raised American bums and aluminium trim replaces the show cars' spars. The good news is that those extravagant wheelarches remain, along with slant-eyed headlamps and a heavily ducted snout. From the front it shouts 'performance and purpose', even if the rear says 'going shopping'.

A conventional road test would start under the bonnet, except the RX's engine sits so far back (to give optimum weight distribution) it's virtually under the front windscreen. The beer barrel-sized, twin-rotor, naturally aspirated engine now has a new design of exhaust port, said to give better control of exhaust emissions and improved economy, and the rotor tip seals now have a target life of almost 150,000 miles instead of 65,000. Two versions will be offered: a ΂£20,000, 189bhp five-speed and a ΂£24,000, 237bhp six-speed model. Mazda hints that a turbocharged version of the RX-8 is on the way and possibly a more sports-biased RX-7 replacement.

For now you get a four-seater with Europe's first modern, rear-hinged (aka 'suicide') doors. Mazda's claim that two adults can sit in comfort in the back is true, but getting in there is a tight squeeze, and once those doors are shut, you are trapped. This is because European legislation demands the rear doors cannot open before the fronts. With no quick-release handle to tilt the front seats forward, rear passengers have to wait in claustrophobic silence to be let out. To ensure that the pillarless RX-8 should be at least as safe in a side impact as a similar-sized four-door saloon, it has 'virtual B-pillars', integral crash beams, locking pins, special steel latches, and side and curtain air bags.

Front seat passengers are rather better catered for. The steering wheel only adjusts up and down, but the seats' every-way adjustment more than compensates for even tall drivers. The chairs are comfortable, with excellent side support.

The facia follows the pattern set by the Mazda 6, with heavily cowelled instruments, piano-black lacquer panels and high-tech circular displays for heating, air conditioning and the ancillary controls; attractive, yes, but a little too shiny and brittle for European tastes. The RX-8 is reasonably practical, however, with lots of storage spaces and a deep boot, just large enough for four adults' soft bags.

Spin the starter and you are rewarded with that typical rotary whirr. Blip the throttle and the rev-counter needle flips up, changing only the engine's pitch, not its volume. You need to use those revs, particularly when pulling away and through the gears, but the clutch and throttle electronics are refined and swapping ratios is no hardship.

Performance isn't a patch on that of the RX-7's, but the RX-8 can wear its sports car tag with pride, particularly the 237bhp model, which is livelier and easier to drive. Top speed is about 140mph, with 0-60mph in 6sec. The overdriven top gear is a tad superfluous, but is presumably there to improve the fuel consumption.

Mazda first signed a licence to exploit Dr Felix Wankel's rotary engine in 1963 under the leadership of the inspirational engineer Kenichi Yamamoto (now 78 years old and an 'advisor' to Mazda). The company spent $50million developing the engine, launching its first rotary-engined car, the Cosmo 110S, in 1967. All along the rotary has been dogged with problems of reliability and excessive thirst. Mazda's solved the former, but is still working on the latter, although one engineer did let slip earlier this year that typical EU combined consumption would be about 22.2mpg.

Ford's best set-up men have been working on the RX-8's handling and it shows. Don't expect kart-style, flat cornering, that's not what this car is all about. The chassis responds accurately, and while the body does roll, it is well restricted. The electronically-assisted steering is reminiscent of the Ford Focus; well weighted, and full of feel and life, but it's the fluidity of the handling that impresses most.

On a smooth track, the Mazda would be outclassed, but on real-world, opposite camber, slippery and bumpy corners, the RX-8 is an agile and super-fast machine. Stability control electronics don't induce the understeer of rival systems, even allowing a small amount of oversteer before reining things in.

With them switched off, the RX-8 is a flattering and controllable machine, with none of the unpredictable oversteer that made early RX-7s so terrifying. The all-round disc brakes are powerful stoppers, with good pedal feedback; anti-lock and electronic brake force distribution come as standard.

All the while the amazing engine whirrs away. Let the revs climb past the limiter's warning beep and it just keeps going; at 9100rpm it was my nerve that gave out, not the engine. It's a remarkable thing and perhaps we should be thankful that Mazda has persevered with it. On the 100th anniversary of Dr Felix Wankel's birthday, he must be rotating (if not spinning) in his grave with delight.