The INFINITI and the Renault Sport Formula One Team did not have the luxury of working from a blank-page design, and instead were bound by the dimensions of the existing Q60. Despite being the most appropriate candidate for the technology, the donor car was not originally devised to accommodate a dual-hybrid powertrain.
The designers and engineers devised several creative ideas to integrate the highly-intrusive dual-hybrid powertrain within the existing body and platform. Rapid digital prototyping of imaginative packaging and engineering solutions became crucial to the success of the project, enabled by the close collaboration between the two Alliance partners and their pared-back design and engineering teams.
The engine bay of the Q60 donor car is packaged in such a way to accommodate the twin-turbo VR30 3.0-liter V6 engine. However, there was initially no space for either of the two MGU-H units, or the independent hybrid cooling circuits. This meant moving and repackaging the existing engine cooling system, and installing a new high-efficiency radiator. A small section of the body has been cut out to accommodate the MGU-H system, with the Atsugi R&D center using its knowledge of the body structure to reinforce the body elsewhere – making the front section of the bodyshell even stronger in the process.
Further back in the car, the MGU-K system, lithium-ion battery pack and ancillary components required even more attention. The rear suspension crossmember has been modified to accommodate the MGU-K. A new cooling system for the MGU-K has been installed, placing the radiator core beneath the rear floor and channeling air through the center diffuser. Advanced computational fluid dynamics software enabled the development team to make a number of alterations to the design of the car’s undercarriage to enable the diffuser and cooling duct to work in parallel with the rear wing to aid cooling and air flow.
One of the most visible change has been the deletion of the Q60’s rear seats, creating additional space for the 4.4 kWh battery pack, energy inverter and hybrid electronic control unit. Following its track car development brief, designers have been free to eliminate the rear passenger compartment, instead creating more space to house the dedicated wire looms required to carry high-power outputs between the different power sources and outlets.
To maximize the impact of the new dual-hybrid powertrain – specifically, using the brakes to harvest kinetic energy – INFINITI and Renault Sport Formula One Team engineers have also replaced existing front and rear brakes with a new brake-by-wire system (as outlined above).
The powertrain itself adds around 200 kg to the overall weight of the vehicle – however, this presented engineers with the opportunity to find weight-savings elsewhere to lower its overall center of gravity, and even redistribute weight for more favorable driving characteristics.
With the introduction of so much additional weight, the development aim for engineers from INFINITI and the Renault Sport Formula One Team was ‘weight neutrality’ - to return the prototype as close as possible to its original 1,752-kg curb weight. The development team succeeded in bringing the curb weight of the Q60 Project Black S prototype back to 1,776 kg – just 24 kg more than the donor car – resulting in a 39% higher power-to-weight ratio.
The steel hood, boot lid, fenders and roof of the standard car have been replaced with lighter carbon fiber panels. As an example, the new hood is 3.02 kg lighter, while the boot lid also weighs 2.7 kg less. The powered glass ‘moonroof’ from the donor car has been removed, with the steel roof panel and assembly replaced with a carbon roof panel to reduce weight at the car’s highest point by 10.2 kg.
The Q60 Red Sport 400’s 20-inch aluminum alloy wheels have been replaced by new 21-inch forged aluminum wheels (275/30 R21 at the front, 295/30 R21 at the rear). Created specially for the Project Black S prototype, the lightweight structure of the wheels means they offset any potential weight gain from their larger dimensions. Wheels are shod in high-performance Pirelli P ZERO™ road tires. The drilled and ventilated carbon-ceramic brakes also offered a significant weight saving. Despite the discs being larger than the Q60’s iron brakes, they provide a combined weight saving of 22 kg. With more powerful calipers fitted accordingly (adding 6 kg), the prototype’s brake system is 16 kg lighter overall than that of the donor car.
Inside, the removal of the rear bench and other rear passenger creature comforts has saved 19.5 kg of weight. The new front seats are also built around lighter carbon fiber shells and feature a slimmer design.
The packaging of the dual-hybrid powertrain also improves the weight distribution of the prototype. The MGU-K and battery pack - located in the rear of the cabin and over the rear axle, respectively – shift more weight towards the rear of the car. Where the base car has a front-biased weight distribution of 58:42 (front-to-rear), the packaging of the powertrain components means the Q60 Project Black S offers a near-perfect 50:50 weight distribution, with mass distributed more evenly over front and rear axles.