When does three plus six equal four? When you're talking about BMW model hierarchy and the all-new 4 Series coupe we recently spotted. The new 4er was being rolled into a car carrier and was wearing minimal camouflage, revealing its very 6-Series-esque design. First off, let's address this numbers game: what was previously known as the BMW 3 Series coupe and convertible is making the change to even numbers for the F32/F33-generation car, hence the 4 Series moniker. The move is similar to the 5/6 Series, and the 1 Series will split into 1 and 2 Series cars for hatchbacks versus coupes and convertibles. The silver 4 Series coupe shown here still had its front and rear ends obscured with camo, but these photos do give us a clear look of the car's profile. Compared with the current 3 Series coupe, the 4 is longer with longer side glass and a slimmer daylight opening. There is a prominent character line running from the front fender back to the taillights that is reminiscent of that on the 6 Series because of the interplay between the convex and concave surfacing. The taillights also look very similar to those from the 6 from what we can see – less so than the smaller units from the 3 Series. Interestingly, there is a small fender vent just behind the wheel well, which looks like it could be functional and not just decoration. Above the vent, we can also see a badge denoting this as a Sport Line car. Not much can be seen of the front end, but don't be surprised if the new grille treatment from the 2012 3 Series sedan makes an appearance here. Our guess is that this 4 Series coupe is powered by the turbocharged 3.0-liter I-6 engine found in the 335i sedan; however, we're not sure if the 4 Series will be called the 435i or adopt a 6-Series-like 440i naming twist. No matter the name, the dual tailpipes, M Sport wheels, and Sport badge denote that this model is definitely aimed at enthusiasts. Expect BMW to also offer the N20 2.0-liter turbo-four in the 4 Series, most likely as the 428i. It's reported that the 2014 BMW 4 Series coupe will make its debut as soon as January at the Detroit auto show alongside the 4 Series convertible, which will, sadly, retain its inelegant folding hardtop.