Speed Week: BMW M4 vs Porsche Cayman GTS

These are the ones that everyone thinks they know - the cliched, sideways-everywhere BMW M car, and the equally cliched, universally brilliant Porsche Cayman. But things are different this year. Sort of... we'll get to that later. The big news is that BMW's core M car is no longer an M3 - the coupe M is now called the M4, while the four-door variant retains the iconic moniker. And that's not all - the straight-six engine makes a welcome return, but now it's turbocharged. Twin-turbo'd, to be precise, with 425bhp and 549Nm, a clever anti-lag system and improved CO2 and mpg. It's an M car for the modern world, outpacing Ms of old, but with a slightly more planet-friendly, efficiency-led and turbo-fed motor under the bonnet