Every two years AC Schnitzer brought something special to the IAA in Frankfurt, alongside news from its range of special parts. In 2003 that was the V8 Topster concept car. The base was a BMW Z4 3.0i, but hardly anything of the original stayed as it was. The most striking change was the closed body, widened by 13 cm and finished in orange and cream.
The heart of the car was the 4,941 cc eight-cylinder, four-valve engine from the M5. It received new intake and exhaust camshafts, reworked cylinder heads, a compression ratio of 11.5:1 and a retuned control unit. Because the engine sat in a different position, the oil pan and oil pump were newly developed. A stainless steel exhaust and a new intake with two air filter boxes completed the work, for 331 kW (450 hp) and 520 Nm.
That was enough for 0 to 100 km/h in 4.5 seconds and a top speed of 305 km/h. The drivetrain and rear axle were modified, with a 3.62:1 ratio and variable locking from 0 to 100 percent. A one-off, 9-way adjustable AC Schnitzer RS coilover suspension lowered the car by 35 mm, helped by new wheel carriers, control arms, anti-roll bars and an aluminium strut brace. It was tuned on the Nürburgring Nordschleife and on public roads.
The new Type IV five-spoke wheels measured 9.0J x 20 at the front and 11.0J x 20 at the rear, on 255/30 and 305/25 R 20 tyres, and the wider body was needed to fit them. A bonnet with a power dome and large vent, a new front apron with integrated xenon high beams, vented front wings and side skirts with ducts to the rear brakes shaped the look. The load-bearing roof also stiffened the body.
Inside, parts from the AC Schnitzer range for the Z4 met one-off pieces such as leather racing bucket seats and Alcantara trim with orange stitching. Early Topster studies also fed into the aerodynamic package AC Schnitzer developed for the Z4, so the family resemblance was intended. The AC Schnitzer record list shows the Topster with 8:16 min on the Nordschleife, 1:13.70 min at Hockenheim and 1:44.4 min at Oschersleben.
Key facts
- Base: BMW Z4 3.0i
- Engine: 4,941 cc V8 from the M5, 331 kW (450 hp), 520 Nm
- 0 to 100 km/h in 4.5 s, top speed 305 km/h
- Body 13 cm wider, suspension 35 mm lower
- Presented at the IAA Frankfurt in 2003
- Nordschleife lap: 8:16 min
