Tradition demands it - every (2) years, at the International Motor Show in Frankfurt, as well as the many innovations in the AC Schnitzer special accessories range, a very special vehicle is presented. And 2003 is no exception: The Concept Car, the AC Schnitzer V8 TOPSTER.

The basis is the BMW Z4 3.0i, in which however "no stone is left unturned". The most striking optical feature is the enclosed bodywork, now 13 cm wider, in colours orange / cream.

The life-giving organ which was developed in record time as a one-off special in close collaboration with the BMW works team Schnitzer Freilassing, is the upgraded performance version of the 4941 cc eight cylinder, four-valve engine from the BMW M5. In conjunction with our technology partner, the engineers have equipped the V8 TOPSTER with special intake and exhaust camshafts. The cylinder heads have also been fine-machined, the compression raised to 11.5 : 1 and the control unit reprogrammed. To improve the exhaust gas flow, an environmentally-friendly special steel high performance exhaust system has been developed with twin chromed racing tailpipe trims in right and left combination.

In comparison with the M5, the power plant has had to be re-positioned in the engine bay of the Z4 basic vehicle and the entire oil circuit optimised, so it was necessary to modify the oil sump and oil pump. Finally, the air flow was improved. By means of new intake pipes and 2 air filter boxes, the entire intake tract could be optimised.

The performance figures are not only the result of the new engine but also a perfect combination of high engine power and optimally adapted power transmission. To match the power of the engine, the drive train and rear axle were also modified. The rear axle, with a gear ratio of 3.62 : 1, has a variable differential lock from 0 - 100 % depending on the load of the V8 TOPSTER. In addition the AC Schnitzer "Short Shift" is fitted.

Perfect retardation is provided by the AC Schnitzer high performance brake kit. This uses larger brake disks of Ø 365 x 32 mm at the front and Ø 328 x 20 mm at the rear in conjunction with special brake calipers (2-piston on the front and single-piston floating caliper on the rear). Even after several "hard brakings", the system achieves deceleration values of 1 g and more.

In motorsport the correct set-up is often decisive for a victory or podium place, and our development engineers place particularly great importance on optimum suspension settings. In the V8 TOPSTER the driving dynamics are decisively improved by the special development of a 9-position adjustable AC Schnitzer racing suspension. As well as lowering by 35 mm in relation to its distant relation - the standard Z4 - the spring and damper rates have been substantially modified towards more sports performance. In addition the wheel bearings and front and rear control arms have been replaced.

To counter sideways body roll, AC Schnitzer developed anti-roll kits on the front and rear axles. A further suspension highlight is the aluminium strut brace which optimally prevents torsion in the vehicle front.

The AC Schnitzer V8 TOPSTER keeps contact with the asphalt through the brand-new racing rims Type IV. The sporting yet elegant 5-spoke wheels have particularly fine filigree work. The individual spokes which run star-shaped from the pentagonal wheel centre to the polished bed perfectly complement the avant-garde TOPSTER outfit. But the wheel and tyre combination is not just an aesthetic highlight. With sizes 9.0J x 20" ET 18 with tyres 255/30 R 20 (front) and 11.0J x 20" offset 0 with tyres 305/25 R 20 (rear), the TOPSTER can corner at speeds otherwise reserved for a thoroughbred Touring Car.

Wheels of this size have to be accommodated somewhere. Just one reason why the bodywork above all had to be adapted to the far higher demands and widened by 13 cm overall.

Even at first glance, the reshaped bonnet of the AC Schnitzer V8 TOPSTER, with its unmissable power bulge and large air outlet, already suggests that beneath it sits a very powerful engine which needs maximum cooling air flow, especially under full load.

Also a new development is the front skirt which gives the TOPSTER an even lower look and considerably improves downforce on the front axle at high speeds. Its large air inlet with integral grille ensures additional cooling for the engine and front brakes, and gives the TOPSTER an unmistakable facial expression. Last but not least, the xenon headlamps integrated into the front skirt ensure that even at night, the driver has excellent visibility.

To take into account the venting of the V8 engine, the new front side walls contain large air vents which, with their 3 chrome ribs and integrated flashers, are reminiscent of the deflectors on the AC Schnitzer ACS4.

But not only at the front of the vehicle must the V8 TOPSTER have adequate air exchange to develop its full potential. This principle naturally also applies to the rear.

Consequently the striking side skirts house air ducts for the rear brakes. The side skirts, which also give the TOPSTER an elongated look, form the harmonious transition to the rear side walls and the monstrous rear. The rear skirt accommodates not only an underfloor wing, but also the complete double exhaust system made of stainless steel.

The specially developed roof, with its supporting function, further reinforces the body of the V8 TOPSTER. With the TOP, the TOPSTER develops a new, homogeneous body side line - similar to a coupé. The integral rear roof wing in conjunction with the two-piece rear wing mounted left and right on the boot, improves the downforce of the entire body.

In the development of the special accessory range for the BMW Z4, even the initial studies of the TOPSTER could be considered. Similarities in the aerodynamic packages available for the BMW Z4 and the V8 TOPSTER are therefore deliberate and technically sensible.

The interior of the AC Schnitzer V8 TOPSTER is a combination of developments in the AC Schnitzer range available for many BMW models, and special one-off products. These include the racing bucket seats in leather. The airbag sports steering wheel, gear lever gaiter and handbrake cover are also provided in Alcantara with orange stitching. Velours foot mats also with orange applications and the leather logo round off the TOPSTER interior.

A carbon-fibre interior and chromed cover for the standard roll-over bar and the aluminium accessories - comprising the pedal set, foot rests, gear knob and handbrake handle - are however components of the standard AC Schnitzer range for the Z4.

The AC Schnitzer V8 TOPSTER was developed as a technology showcase. In the equipment level and form shown here, this concept car would cost around € 185,000.00. Series production is not planned.

Story by AC Shinitzer