Next generation 1-Series may get a 5-door 135i with the new N55 petrol single turbo, twin scroll straight-six engine with 302 hp (225 kW / 306 PS) recently introduced in the current 135i coupe and cabriolet models.

This is the first time we've spotted a 3-door prototype of the upcoming next-generation BMW 1-Series.

Looking closely at the camouflage in the high-resolution photo, it appears that a seam line has been marked with black tape to portray a rear door outline, although no door is there.  Another clue is the angled b-pillar.

Previously, we've seen only 5-door variants of the next-generation 1-Series prototypes. But both body styles reveal the 1-Series sleeker, more extended look. If not in actual dimensions, the new design may just make the 1-Series look less compact.

And in those previous set of shots we spotted a 5-door 1-Series prototype carrying some of the markers of the current 135i, with the single, round tailpipes at each end of the rear, hinting that we will see a 135i with the new N55 petrol single turbo, twin scroll straight-six engine with 302 hp (225 kW / 306 PS) recently introduced in the current 135i coupe and cabriolet models.

The next-generation BMW 1-Series is expected to debut next year (2011) as a 2012 model.

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