Seventy years ago, BMW’s racing division celebrated its greatest racing triumph so far in the world of motor sports by winning first, third, fifth and sixth places at the 1940 Mille Miglia with its classic 328.

To honor this anniversary, BMW Group’s Italian arm has created a special edition version of the firm’s hardtop roadster called the Z4 sDrive35is Mille Miglia, of which only 99 examples will be sold in Italy.

Based on the standard Z4 sDrive35is that’s powered by a twin-turbocharged 3.0-liter straight-six with 340HP, the Mille Miglia edition comes equipped with an M Sports aerodynamics package and 19-inch alloy wheels in a dark chrome shade, while the body is finished in a matte silver color called ‘Polaris’.

Other exterior highlights include the ‘Mille Miglia’ badges and the matte black kidney grilles.

Inside, the most noticeable feature of the Z4 sDrive35is Mille Miglia are the sports seats covered in Alcantara and leather with contrasting red stitching. The car also gets an M Sport steering wheel, unique floor mats, ‘Mille Miglia’ badges and special decorative trim.

While BMW had pretty much ruled out the possibility of creating a successor to the M variants of the Z3 and the previous Z4 with its new hardtop roadster, no one from Munich ever said that there wasn’t going to be a faster and more focused version than the Z4 sDrive35i.

That car is the Z4 sDrive35is -the ‘s’ is what makes the difference- and it will make its world debut at next month’s 2010 Detroit Auto Show before going on sale worldwide in Spring of the same year.

Bypassing BMW’s ridiculous naming system (Z4is or Z4 35is would have been just fine), the range topping Z4 features a more powerful version of the company’s 3.0-liter twin-turbocharged straight six and M-Sports styling and chassis packages.

At the heart of the Z4 sDrive35is is BMW’s 3.0-liter twin-turbo straight-six that benefits from optimized air supply and increased boost pressure. Output is lifted from 306HP to 340HP at 5,800 rpm while peak torque is increased to 450Nm or 332 lb-ft and is available from 1,400 rpm all the way to 4,500 rpm.

Furthermore, the modified engine management on the Z4 sDrive35is also allows the use of an Overboost function briefly increasing engine torque under full load by another 50Nm or 37 lb-ft to 500Nm or 369 lb-ft.

Power is driven to the rear wheels through a revised version of the firm’s seven-speed double clutch transmission with BMW announcing a zero to 100km/h sprint time of 4.8 seconds (0-60mph in 4.7sec) and an electronically limited top speed of 250km/h or 155mph.

BMW says that despite the increased performance over the standard Z4 sDrive35i, the ‘S’ model delivers the same fuel economy averaging 9.0lt/100km which is equal to 26.1 mpg US with CO2 emissions rated at 210g/km.

Aside from the powetrain upgrades, the Z4 sDrive35is also comes as standard with an M Sports Package including the M Aerodynamics Package and adaptive M Suspension.

The M Suspension, which features electronically controlled dampers, lowers the entire car by 10 mm or almost 0.4-in. The top-Z4 also gets a reprogrammed electronic power steering system that promises to offer increased feedback.

On the outside, the M package adds unique 18-inch alloy wheels with 19-inch rims available an option, a new front bumper, re-trimmed kidney grilles, matte silver exterior mirror caps, a new rear bumper with an integrated diffuser and specific tail pipes.

Finally, the interior has been enhanced with several features such as the M leather steering wheel with gearshift paddles, M footrest, sports seats, aluminium carbon trim, BMW Individual roof lining, M entry strips and footmats with coloured piping.

The revised instrument cluster with grey faces on the dials and the “sDrive35is” model designation complete the package.

If we are to believe a report from UK digital car magazine i-Motor, BMW has cancelled the development of an “M” version for the new Z4 roadster with the retractable hardtop because of the “ongoing financial crisis” and “lack of customer demand”. Here’s what the BMW spokesman -whose name was not disclosed- revealed to the British magazine: “Given the current economic crisis there is no business case for a full-on M version of the Z4″.

If that’s the case, then how can one explain the introduction of the X5M and X6M crossovers that are due to be unveiled this April?

Well, according to the unnamed spokesperson, the M-prepped variants of both the X5 and X6 were already under development and had been given the green light from the company’s officials before the car market crashed down.

While we’ll have to wait for some sort of official announcement from BMW to see whether or not the car has been truly canned, we must say that even though the X5 and X6M’s development (may have) proceeded that of the Z4Ms, we fail to see the logic behind a decision that prefers two (totally unnecessary) M crossovers over an M roadster model, especially since the X5 and X6 are already offered with a mighty 408HP twin-turbo V8 engine.

We never know exactly what we’re going to get when BMW introduces a new product. Most agree that the new 7-series is a visual improvement over the vehicle it replaces, but then there are all-new vehicles like the X6 that we’re still trying to figure out, both from an aesthetic and functional point of view. We do, however, know exactly what a roadster is for and are often swayed by powerful turbocharged engines, so this new Z4—with its updated styling, optional turbos, and retractable hardtop—is likely to win us over.

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