The V8 biturbo engine of the Cayenne Turbo GT is currently the most powerful eight-cylinder engine from Porsche. Its additional 67 kW (90 PS) corresponds to a power hike of approximately 16 per cent compared with the engine of the Cayenne Turbo, which serves as its basis. The most extensive engine modifications have been on the crankshaft drive, turbochargers, direct petrol injection system, and on the intake and intercooler systems.
The internals of the GT model’s eight-cylinder engine differ with respect to fundamental components such as the crankshaft, connecting rods, pistons, timing chain drive and torsion vibration dampers. In view of the increased power, these components have been designed for higher load peaks and driving dynamics. In some cases, new materials have been used to further and significantly enhance the engine's robustness during track use. New fuel injectors supply a flow rate that is approximately ten per cent higher than before with an unchanged maximum injection pressure of 250 bar.
The engine's entire airflow system has been designed for increased throughput. Larger air/water intercoolers allow a higher volume to pass through, and the turbochargers have larger compressor wheels. Both efficiency and power have been increased in combination with a maximum boost pressure raised to 1.6 bar. In order to improve responsiveness and performance, turbocharger pre-loading has been increased at higher engine speeds. This means that a boost pressure reserve is built up between the turbocharger and throttle valve in partial load and overrun operation, which is then released when the driver presses the accelerator and transformed into instantaneous torque output. To prevent the knock limit from being exceeded, the engine's compression ratio has been reduced from 10.1:1 to 9.7:1. Three additional radiators ensure that the driver can call on the engine's power continuously and without restrictions under all conditions.
Custom design: titanium sports exhaust system
The standard sports exhaust system, with its centrally positioned tailpipes, is bespoke. From the middle of the vehicle, the exhaust gas tract including rear silencers is made of titanium. This material is significantly lighter than the stainless steel used directly in the tract from the engine and is also characterised by high corrosion and temperature resistance. The centre silencer is also omitted on the Cayenne Turbo GT. Overall, the sports exhaust system is around 18 kg lighter than the one on the Cayenne Turbo. The two exhaust branches are routed separately from each other. A continuously adjustable flap in each branch fully or partially opens a bypass around the main silencer, depending on load and engine speed. The effect is a particularly distinctive sound, which takes its inspiration from the motorsport arena and differentiates the Cayenne Turbo GT acoustically.
Modified eight-speed Tiptronic S changes gear faster and more emotively
The eight-speed Tiptronic S already behaves in a noticeably different way to the automatic transmission in the Cayenne Turbo, even in Normal mode: changing gear more quickly and accompanying downshifts with an emotive crackle on the overrun. In Sport mode, the reaction times for gearshifts are shorter, and there is distinct acoustic feedback. Sport Plus mode is designed for maximum performance. It offers the optimum set-up for the racetrack and was developed on the Nürburgring Nordschleife. Sport Plus mode also allows a lower gear to be manually preselected during braking, which is then automatically engaged as soon as the engine speed permits.
The significant increase in power and racetrack-capable driving dynamics also required a special set-up for the all-wheel-drive system. This is because the instant power delivery of the twin-turbocharged V8 can potentially lead to wheelspin sooner. The response of the Porsche Traction Management (PTM) control system has therefore been made even faster and the power distribution optimised for the demands of the racetrack. The PTM uses variable and adaptive strategies to control the power distribution between the rear and front axles. In addition, the system continuously monitors driving conditions and preloads the all-wheel-drive system as a preventive measure if necessary. As a result of the higher load peaks, the thermal limit range of the hang-on system has been shifted upwards. A gearbox water cooling system installed exclusively for the Cayenne Turbo GT counteracts this effect.
