Those itching to know officially what engine lies beneath the shapely bonnet of the new 2015 Mazda MX-5 won't have too long to wait, with the full suite of technical information to be revealed at the Paris motor show at the start of October.

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Mazda this week tore the covers off the fourth-generation MX-5 to much fanfare in three locations simultaneously -- Spain, the US and Japan. But much of the data about what lies under the skin remains under wraps.

Here's what we know for sure. It will be the shortest MX-5 ever, it will weigh less than any version since the 1989 original at about 1030kg and it will launch as a soft-top only. It will also be the first properly new model with all new underpinnings since the NA original.

In time expect to see a hard top offering. Expect also to see another sportscar spun off this platform to amortise costs -- a strategy that complements Mazda's move to license the underpinnings to Fiat for the new 'Barchetta'.

Mazda MX-5 shots2

Whether this new coupe wears RX-7 badges is the big question, and it's one Mazda refuses to discuss.

Under the polarising new MX-5 design sits a brand spanking new rear-drive platform, the first of this configuration to fall under Mazda's lightweight SkyActiv program. The engines -- yes, plural, in another first (multiple engine options, that is) -- will be longitudinally mounted.

While Mazda staffers are sworn to secrecy, expect the base engine to be a derivation of the 1.5-litre unit from the new Mazda2, tuned (but not turbocharged) to somewhere close to the current 1.8's 118kW and 188Nm atmo unit.

Above this will be a version of the CX-5's and Mazda 3's 2.0-litre naturally aspirated engine with somewhere nudging 130kW. As ever, Mazda says, less is more. So don't expect big horsepower.

Six-speed manual and six-speed automatic gearboxes will be offered, as will Mazda's MZD infotainment system with a dial mounted between the seats.

All will be revealed in Paris. Stay tuned for le big premiere.