Schweinfurt. The 8HP ZF automatic gearbox has proven its qualities in the BMW M235i Racing Cup since the 2014 season. In 2015 ZF introduced the next evolution – the 8P45R motorsports gearbox. It is even more dynamic, lighter and consequently perfectly suited for use in motorsports. The 8P45R had its first successful track appearance at the VLN at the legendary Nürburgring. Porsche also relies on the competencies of ZF Race Engineering in the new Cayman GT4 Clubsport.
Previously, an automatic gearbox was considered a somewhat unusual construction in motorsports; however, ZF paved the way for this new solution during the 2014 season. The automated 8HP gearbox eases the workload considerably for BMW M235i Racing Cup competitors, and allows the racing drivers to stay almost completely focused on their environment and on the track. Mechanical damage as a result of shift mistakes is also excluded as are fatal blockages and dynamically unbalancing shocks on the driven axle.
Whereas the previous automatic gearbox was based on a standard production line design and modified software, ZF now sees good potential for a pure motorsports planetary gearbox. The aims of the redesign: ratios, shift points and shift speed should fulfill the greater demands in motorsports without compromise. ZF also attached value to low weight.
The designers retained the fundamental design and assembly scheme – comprised of four planetary gear sets and five shift elements – from the previous 8HP gearbox. One of several new features is the omission of a converter in the gearbox. The pulling away or drive-off process is implemented by internal shift elements. A vibration damper upstream from the gearbox input prevents damage through engine oscillations. The gear ratio spacing is closer and the rev drops between gears have been reduced. Normally only the first six gears of the former 8HP gearbox were used when racing. In the new transmission all eight gears are spaced sensibly in the operating range.
By omitting the converter and other reduction measures, the designers saved about 15 per cent on weight. The internal power loss was also reduced significantly. The 8P45R gearbox is currently available for the BMW M235i. In the future, it is also envisaged for use in other manufacturers’ sportscars.
Porsche also relies on the competencies of ZF in the new Cayman GT4 Clubsport. In 2016 the Porsche engineers developed a racing version of the well-established Porsche Dual Clutch Transmission (PDK) together with ZF Race Engineering. A special development focus was put on adapting the series gearbox to the increased demands in racing with regards to shifting times, functions, reduced weight and improved durability while maintaining optimum performance.