The BMW M3 CS has been snapped during testing, providing a peek at the upcoming hot four-door.

Like the two-door M4 CS, it builds on the base four-door M3 body with a carbon fibre bonnet and splitter, along with a gurney spoiler on the bootlid. All the same touches feature on the M4 CS.

Power is expected to come from the 338kW turbocharged inline-six engine found in the M4 CS, making this the most powerful M3 ever.

As with the two-door, expect the M3 to be dual-clutch only, with the manual limited to Competition or Pure-spec cars.

Rolling on a set of sticky Michelin Pilot Sport Cup 2 tyres, the car is expected to lap the Nurburgring in less than 7:40.

Given the current four-door lap record holder at the Nordschleife, the Alfa Romeo Giulia QV, set a 7:32 last year – although rumours suggest the Jaguar XE SV Project 8 is chasing a new record at the moment – that would make the M3 CS a seriously quick family sedan.

The CS will sit above the Competition in the M3 range, but below the M4 GTS in terms of performance. Along with the exterior changes, you can expect to see lightweight touches – like straps instead of door handles – scattered throughout the cabin, and the requisite swathes of Alcantara on all the touch points.

When it launches, the M3 CS is expected to be built in limited numbers. Just 3000 examples of its M4 equivalent were produced, so we'd suggest the same number of four-door examples will be up for sale.

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