...what is the main difference between a regular Z4 and and M Z4 ? turbo ? or is just engine displacement ?

Just engine displacement,there are two different six cylinder engines on the two Z4 coupe versions. The 3.0si develops 315 Nm of torque from 2500, meaning it does 0-100 km/h in 5.7 seconds. Meanwhile, he 3.2 litre unit in the Z4M does it in 5 seconds flat. The maximum torque is available at 2000 rpm. It’s an engine that is quite simply a superb mix between violence and flexibility.