BMW has released another teaser for the upcoming i8 Roadster, which is rumoured to make its global debut in Frankfurt later in September. The i8 Roadster was first previewed by the i8 Spyder Concept that was first revealed way back in 2012, so this one’s a long time coming.

The video does show quite a lot of the open-top i8, although most of it is mainly of its front, which is nigh identical to its coupe sibling. Shots of the vehicle’s rear are fewer in number and pretty blurry, although most of details look pretty similar to those seen in spyshots of prototypes in the past.

This includes the i8’s familiar flying buttresses, which appears to cover a wider surface area than on the coupe. The folding soft-top requires a total redesign of the rear deck lid to include the necessary moving parts and rollover protection, the latter resulting in those humps.

A by-product of this transformation is the i8 Roadster’s frameless doors, which should offer just as much visual drama as the framed doors on the coupe. Given its strong links to the coupe, we reckon the i8 Roadster’s interior won’t detract too far from what is found in the hardtop, albeit with minor updates.

Similarly, the i8 Roadster will use the eDrive system as seen on the i8 coupe, which is made up of twin electric motors and a 1.5 litre turbo three-cylinder petrol engine. Reports indicate the plug-in hybrid powertrain will receive technical improvements so it offers increased output and efficiency.

More details will be known when the i8 Roadster is revealed in full, including how it performs relative to its hardtop sibling.

GALLERY: BMW i8 Roadster spyshots