PORSCHE is doubling the number of its cutting edge Gran Turismo Sport performance models with the arrival of both Cayman and Boxster GTS versions.

The dynamic duo add to the existing Cayenne and Panamera GTS variants.

In the case of the Boxster, which will cost from £52,879 when it arrives in May, the two-seat roadster comes with a more powerful engine plus an uprated chassis.

Beneath the bonnet is an optimised version of the Boxster's 3.4-litre engine which has been tuned to produce an extra 15bhp - taking its output to 330bhp - while pulling power has also been boosted to 370Nm.

The brand's Sport Chrono package and Porsche Active Suspension Management are also fitted as standard, letting the driver modify damper stiffness and change the throttle characteristics of the engine.

And in conjunction with the optional PDK double-clutch transmission, the Launch Control function enables the Boxster GTS to blast from 0-62mph in 4.7 seconds.

With the standard manual six-speed transmission the GTS is the first Boxster to offer the potential to top 174mph, yet can return an overall fuel figure of 31.4mpg or 34.4 with PDK.

As for styling there are black finish 20-inch Carrera S alloy wheels, a front spoiler, re-styled lower apron and black finish Bi-Xenon headlights - with the Porsche Dynamic Light System as standard -  while inside there are sports seats and leather trim.

The Cayman GTS becomes the most powerful and fastest edition of Porsche's mid-engined coupe and also boasts an uprated engine and sharpened chassis responses. It too is available in May and costs from £55,397.

The six-cylinder boxer engine in this version is also based on a 3.4-litre unit and gets an extra smack of punch taking its output to 240bhp and torque figure to 380Nm.

Acceleration is from 0-62mph in 4.6 seconds - 0.3 secs quicker than a standard Cayman S with PDK - and with the standard manual six-speed transmission a top speed of 177mph is possible.

Fuel consumption and styling elements are identical to the Boxster.