A Swiss tuner has made a 203mph BMW M4 Convertible

“The M4 Convertible does twist and shimmy a bit when you drop the roof, betrayed by the steering wheel shaking in your hands, but the handling precision doesn’t noticeably change.”

So said TG when we drove the BMW M4 Convertible back in 2014, with its 425bhp twin-turbo six-cylinder engine.

What, then, will this rather more powerful open-top M4 feel like? It’s the work of Switzerland’s Daehler Design & Technik, and it has rather more power than standard.

Just how much more is up to you: a Stage 1 kit yields 503bhp and 517lb ft (increases of 78bhp and 111lb ft), enough for a 0-60mph sprint of four seconds dead and a top speed of 196mph.

But it’s the Stage 2 kit you’re really interested in. The hikes are more profound, as you might expect, and an M4 thus equipped produces 532bhp and 539lb ft. Want some context? It’s power equivalent to a Porsche 911 Turbo and a torque figure to eclipse a Ferrari F12 tdf’s. Yikes.

It all adds up to a sub-4.0sec 0-60mph time and a quoted 203mph top speed. We fear the steering wheel may shake a little more than standard at that sort of speed.

Thankfully you can specify some upgraded brakes and 18-stage adjustable coilovers to help keep everything under control…