BMW is currently working on a replacement for the Z4 Roadster. Codenamed E89, the new Z4 will be a conventional soft-top and will come as a competitor for the next generation Porsche Boxster and Mercedes SLK-Class. It will be priced somewhere around $40.000.

The next generation Z4 will be about the same size as the current Z4, but will probably wear a less controversial design with a wider track and more dynamic proportions. The highlight of the new model is its high-tech structure—a combination of aluminum space frame and steel unibody construction.

The silhouette is recognizably a Z4, but the disguise is unusually thick, suggesting that the design might be more different than meets the eye under those same-again proportions. Some of the more unusual ’banana’ swage lines could be toned down, but the E89 model will still be aimed squarely at the Porsche Boxster and Mercedes SLK.

Next to the conventional soft-top model, engineers might also consider a modern folding hard-top configuration. The current machine shunned the fashion for the latter in favor of a rag-top design, and if the company goes down this route again, stylists will be able to retain the long-nosed proportions of the existing car. However, using a soft-top would be in direct contrast to key rival the Mercedes SLK, which has used a clever folding hard-top since its introduction in 1996.

Beneath the skin it will feature active steering, adjustable dampers and a new twin-clutch transmission (replacing the sequential M gearbox) along the lines of VW’s DSG box. The chassis will be much stiffer, to the benefit of ride and handling.

The 2009 Z4 will have three different choices of engines, and another one more powerful coming after. The first one is a 2.0-litre direct-injection with an output of 185 hp. The second one is a direct-injection 2.5-litre Inline-6 with a power of 231 hp. The third one is a Turbocharged 3.0-litre direct-injection rated at 321 hp. The more powerful one is a high-revving normally aspirated 4.0-litre V8 with an output of 450bhp.

It will be electronically limited at 155 mph and will make the 0 to 60 mph sprint in less than 6 seconds.

If you are a fan of the Bavarian brand will have to be patient because the new Z4 is not expected to hit showrooms until 2009.

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History

The BMW Z4 is a rear-wheel drive sports car by the German automaker BMW, known as the E85 in roadster form and E86 in coupe form. Production started in 2002, and thus replaced the BMW Z3.

The Z4 was designed by Chris Bangle and began the controversy over his "flame surfacing" design and aggressive styling choices, which can also be seen on most modern BMW cars, most noticeably the 7 Series and 5 Series. As of 2006, the entire BMW car line, including the BMW 3 Series, had incorporated Chris Bangle's design theme.

When the Z4 roadster was introduced it was a significant leap forward from its highly successful Z3 predecessor. Indeed, the Z4's debut was much more than just 'successor replaces predecessor,' for the new Z4 roadster put BMW in a more elevated, sophisticated segment of the roadster market.

The Z4 places BMW squarely in the field of sophisticated, full-featured sport roadsters. It comes exclusively with 6-cylinder power and offers a choice of four transmission types. Its chassis engineering is new, encompassing multi-link rear suspension, standard run-flat tires and wheel/tire diameters up to 18 inches. The Z4 offers amenities and options never before seen in a regular-production BMW roadster. Safety engineering and features have been further developed.

Z4 2.5i. 2.5-liter, with 184 horsepower and 175 lb.-ft. of torque. This unit delivers 0 to 60 mph in 7.1 sec. (manual trans., BMW AG test results) and achieves the amazing top speed of 146 mph. Its EPA mileage ratings are impressive too: 20 mpg city/28 mpg highway with 5-speed manual transmission, 20/29 with the optional 6-speed Sequential Manual Gearbox (SMG), and fully 21/28 with the available 5-speed automatic. Top speed is 137 mph with the 5-speed, 146 with SMG and 141 with the automatic.

Z4 3.0i. 3.0-liter, with 225 hp and 214 lb-ft. of torque. This version is further refined for an even more exciting sound. Motor Trend noted in its May '03 issue that 'It delivers an impressive amount of power, with vibration evident only by its absence…Underway, dual exhaust tips broadcast a turbine-like mechanical growl that's wired directly to the driver's right foot.' This engine powers the Z4 3.0i to 60 mph in just 5.9 sec. with the standard 6-speed manual transmission or optional SMG, and reaches 60 mph in only a tick more at 6.0 sec. with automatic (BMW AG test results). Top speed is electronically limited to 155 mph with the manual transmission or SMG; with the automatic it is a 'natural' 152 mph. With its manual transmission, the Z4 3.0i earns excellent EPA mileage ratings of 21 mpg city / 29 mpg highway; with SMG the ratings are 20/29 and with automatic 19/27.

In 2006, BMW updated the Z4 line by installing its new N52 I-6 engines. In the 3.0si, this engine makes 255 bhp and 220 lb-ft of torque. The N52 features magnesium block construction and BMW's Valvetronic variable valve timing system. Although the new engines represent a modest upgrade in power over the M54, they are considerably more robust throughout the middle of the rev range. Moreover, they improve fuel economy noticeably. A final benefit of the N52 engines (the lightest production 6-cylinder engines in the world) is that they improved handling and turn-in due the the decreased weight over the nose of the car. Oddly, this is particularly noticeable in when compared to the Z4 M, as it carries the rather heavy S54 iron block engine. In addition to the powertrain updates, BMW made mild revisions to the styling of the Z4, added several electronic features, and increased the brake size on the 3.0si models.

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Competitors

2008 Porsche Boxster

In 2008 Porsche will unveil a new Boxster with subtle styling changes and incremental boosts in power.

Comparing to 2005 Boxster, the new model will feature an updated front fascia and LED headlamps and also redesigned, and much rounder, air intakes. Also there will be new ear bumper and completely new LED taillights. These changes are also expected to appear in the next Cayman coupe.

The 2008 Porsche will be powered by a Flat-6 engine delivering around 270 hp. This will help the new Boxster to sprint from 0 to 60 mph in 5.9 seconds and have a top speed of 165 mph.

2010 Mercedes SLK-Class

For 2010 Mercedes is preparing a replacement model, the third generation SLK. Wearing the internal code R172, the 2010 model will have to face a matching competition. The SLK Mk I had the advantage of being the only roadster/coupe at the launch time. Even the Mk II, only had to face a few competitors, but by 2010, almost every roadster will feature a foldable hardtop option.

The 2010 SLK will feature a very dynamic design, making of serious departure from the styling of the previous models. This design revolution will be required in order to maintain the SLK’s technological advantage to the competition.

The foldable roof will most probably benefit from a completely new design. The current SL already uses a more sophisticated three-piece roof. Until 2010, Mercedes will have plenty of time to develop a completely new converting system. One of the disadvantages of a retractable hard-roof in comparison with a soft-top is that it adds a lot of weight, therefore diminishing performance. This is one matter that Mercedes will definitely struggle to remediate.