Modena, Italy  - Italian sports car maker Maserati has expanded its range with an upgraded version of the Quattroporte and has hinted at a new drop head model for the autumn.

The four-door limousine is already no slouch and thanks to an extra 10 brake horsepower from its 4.7-litre engine, the makers in Modena promise enhanced performance.

Revised software for the six-speed automatic gearbox enables the V8 unit to rev happily above 6,000 rpm, freeing up more power for acceleration and top speed.

The Quattroporte Sport GTS will bound from 0 to 100 km/h (62 mph) in 5.1 seconds and reach 285 km/h, if driven to the limit. It also boasts firmer suspension and lightweight alloy wheels. The new car is recognisable by its matt black grille and modified headlamp treatment.

Meanwhile, industry sources say a new cabriolet based on the two-door Grand Turisimo is set to bow in at this year's Frankfurt car show from September 17 to 27.

According to Maserati's chief engineer, Paul Fickers, the new Spyder is far more likely to happen than a rumoured cut-down Maserati designed to compete with the likes of Porsche's mid-range Cayman.

"At difficult times like these, the chances of such projects are on the slim side," he told Germany's auto motor und sport journal. (dpa)