The Alfa Romeo 4C Spider has been unveiled in prototype form at the Geneva motor show, sporting a canvas roof, plus different headlight, wheel and exhaust designs over the coupé. It will go to production in early 2015.

Alfa says the car’s weight gain has been limited to 60kg over the coupé, thanks to the use of a lightweight canvas roof, plus carbon-fibre rollover hoops, spoilers and windscreen frame. Alfa also says it has crafted the aerodynamics of the car to minimise roof-down turbulence.

The new dual-stage central exhaust system uses titanium and carbon tail-pipes, and has been developed by renowned motorbike racing exhaust manufacturer Akrapovic, which has worked in MotoGP, Superbikes and Motocross. It has an electrically-operated valve system, which can improve performance and enhance the exhaust note at the push of a button.

The cosmetic changes are notable for focussing on two areas of the coupé that have drawn the most criticism so far. It is not clear, however, if the new carbon-fibre clamshell headlights and milled aluminium wheels, finished in a gloss white paint, are set for production, or if they are if the changes would also be applied to coupé.

The 4C Spider is otherwise identical to the coupé, with power coming from the same four-cylinder, all-aluminium, 1750cc turbocharged petrol engine which drives the rear wheels via a six-speed, dual dry-clutch Alfa TCT transmission. Alfa says 0-100kph takes 4.5sec and top speed is in excess of 250kph - the same as the coupé. Weight distribution also remains 40:60 front-to-rear.

Finally, to complement its show-stopping presence, new carbon-fibre clamshell headlights have been fitted to the Alfa Romeo 4C Spider prototype, as have unique alloy wheels, milled from solid aluminium blocks, shod with bespoke Pirelli tyres. It's finished in three-layer gloss white, which helps emphasis the car’s sculpted shape and resolved surfaces.