Porsche Panamera Sport Turismo unveiled.

Porsche has provided the clearest hint yet that its long held plans to expand the Panamera line-up to include a sporting estate have already progressed past the crucial decision-making stage and into the realms of new model development, with the unveiling of this production realistic concept car, the Panamera Sport Turismo

The up-market five-door, which showcases a development of the existing Porsche petrol-electric hybrid system complete with plug-in capability for the first time, is one of at least three new Panamera-based models Zuffenhausen bosses have been mulling over since the introduction of today’s liftback model to the line-up back in 2009. Visual changes over today’s liftback include an extended roofline, longer glasshouse and angled tailgate that opens at bumper height.

The unveiling of the Audi A6 Avant and Mercedes-Benz CLS Shooting Brake rival in concept car form at the Paris motor show is set to proceed an official announcement from Porsche boss, Mathias Muller, confirming the new style-led estate will form part of the second-generation Panamera line-up, whose platform structure will be shared with future Bentley models as part of closer engineering ties being forged between the two Volkswagen Group-owned companies.

“The body concept of the Panamera Sport Turismo is an outlook on a possible Porsche sports car of tomorrow,” says Porsche, without providing any official time line for the introduction of the production version. However, sources close to the German car maker say the new estate will make its market debut in 2016, with production set to take place alongside a successor to the liftback at Porsche’s increasingly active Leipzig-based factory, which also turns out the Cayenne and is also set to handle production of the upcoming Macan as well.

Porsche investigated spinning an estate off the current Panamera design but the high cost of re-engineering its rear body structure, including vital changes to the bulkhead to allow through loading, ultimately proved prohibitive. As such, the new model has been integrated into the development process of second-generation Panamera line-up from the start, ensuring its production can be amortised with other models. “In terms of the overall concept, the estate is not too far removed from the liftback. Both use a large tailgate, with the structure engineered appropriately to suit both,” Autocar was told.

The decision to push ahead with plans for a Panamera estate has increasingly been driven by customer feedback, according to Porsche. “We have existing Panamera owners who seek greater practicality but don’t necessarily see the Cayenne as a solution.” While no official figures have been quoted for the size of its luggage compartment, the Panamera Sport Turismo is said to offer over 200-litres more than the Panamera liftback, which holds 445-litres. This would place it close to the A6 Avant, which is good for 565 litres, and the CLS Shooting Brake, with its generous 590-litres.

As well as formalising plans for a new Panamera estate model, the Sport Turismo also provides solid clues to the appearance all second-generation Panamera models will take into production. The classic proportions remain, with a long sweeping bonnet dominating the side profile. However, there has been a conscious effort to rid the new car of the bloated look of the existing liftback, with tauter surfacing treatment and the use of subtle creases within the body.

Among the details developed by Porsche design boss, Michael Mauer, and his team of in-house designers are newly shaped headlamps with distinctive double decker LED graphics, a more heavily contoured bonnet, greater structuring to the flanks with a reinterpreted version of the brake cooling graphic incorporated behind the front wheel arches, a more prominent lip to the rear wheel arches to accentuate the stance and thinner LED tail lamps that, in a nod to certain 911 models, are connected by a reflector strip in a move that provides it with greater visual width than today’s model.

At 4950mm in length, 1990mm in width and 1401mm in height, the new Porsche concept car is a minimal 20mm shorter, 60mm wider and 19mm lower than the soon-to-be-facelifted Panamera liftback. By comparison, the Mercedes-Benz CLS Shooting Brake is 5000mm long, 1881mm wide and 1412mm high.

As well as previewing its plans for a new up-market estate, the new four-wheel concept car also showcases a powerful new plug-in hybrid drive system. Porsche intends to begin offering this system with the second-generation Panamera and facelifted second-generation Cayenne from the middle of the decade, as part of its Intelligent Performance initiative.

Called e-hybrid, the Porsche developed system uses an upgraded version of the existing Panamera hybrid’s brushless synchronous electric motor, mounted within the forward section of the gearbox housing delivering 94bhp. It is supported by the same Audi-sourced 328bhp supercharged 3.0-litre V6 petrol engine used today.

Together, the electric motor and combustion engine provide a combined system output of 410bhp – a good 35bhp more than today’s Panamera hybrid and sufficient, according to Porsche, to propel the next-generation model from 0 to 100kph in less than six seconds.

Energy for the electric motor is provided by a 9.4kWh lithium-ion battery sited within the floor of the boot. It is planned to replace the nickel-hydride battery used by the current Panamera hybrid, with plug-in compatibility allowing it to be externally charged within 2.5 hours via a high voltage wall-mounted charger.

Another facet of the Panamera Sport Turismo that is tipped to be adopted on future Porsche models is its new graphics-based instruments and touch-sensitive interior control architecture conceived in-house.