Our spies have lifted the lid on the next-generation BMW Z4 – and the big news is that it’s getting a folding metal roof for the first time!

BMW has been keeping their new Z4 roadster under tight wraps with big lumpy plastic pieces to cover any hint to the car. But recently we have seen the first of the next gen-Z4's with just tape on the Nurburgring. And even if it does not reveal all that much about the design details, these latest photos to confirm that the new SLK rival will have a metal roof. It will be the first time BMW covers its roadster with a hard-top following in the footsteps of the BMW 3-series Convertible.

But besides being an SLK rival, BMW is also gunning for the Porsche Boxster. A full range of engines should put the new Z4 alongside the Boxster, including the twin-turbo 3.0 liter straight six-cylinder unit. Also, jumping on the bandwagon, BMW is contemplating to offer a diesel engine while the range-topping Z4 M will see the new 4.0 liter V8 under the bonnet. All Z4's will feature BMW's Efficient Dynamics in order to cut CO2 emissions and boost fuel economy.

The next generation Z4 will only be an inch or so longer and wider than the outgoing model. Now that the big plastic covers have come off our carparazzi have finally been able to make some educated guesses. We are expecting the new Z4 to go on sale late 2009.

Gallery: New BMW Z4 Spied Again