It was just under five years ago when the BMW i8 Spyder Concept first broke cover ahead of the 2012 Beijing Motor Show, and now the topless, mid-engined plug-in hybrid has been spied undergoing road testing.

The upcoming Spyder is expected to use the powertrain from the coupe, though likely in updated form as the fixed-roof version is expected to receive a mid-lifecycle update, with an uprated powertrain. Though exact details are scarce, the i8’s electric motor is expected to provide greater output than the unit in the current model, with 131 hp and 250 Nm of torque.

Paired with the 1.5 litre, turbocharged three-cylinder petrol engine which is also expected to receive updates and greater output, total system output is estimated at 420 hp, according to an earlier Autocar report. New software for the i8’s six-speed automatic transmission should also provide gains; as the coupe is set to be updated before the Spyder’s debut, the latter should naturally benefit from these as well.

A more energy-dense battery pack is also expected to make it to the i8 coupe update and consequently the Spyder as well; the i8-based safety cars for Formula E use a larger 10kWh battery compared to the standard car’s 7.1 kWh unit, and here too an improvement can be expected for the upcoming i8 duo.

The facelifted i8 coupe and by extension the Spyder, too, could also draw upon the Formula E safety car for possible chassis tweaks; possible changes include modified upper wishbones and mounting points with revised springs and dampers, while the 15 mm drop in ride height on the safety cars could be adopted for the facelift – and the upcoming Spyder – as well.

The i8 Spyder is slated for a 2018 debut, according to BMW CEO Harald Krueger in an earlier report, which could mean the i8 coupe will debut in updated form slightly earlier, which could be later in 2017.

GALLERY: BMW i8 Spyder Concept