The WRC is leaving behind the 70th anniversary edition of the Rally of Finland, to project itself towards the two final rounds of the 2021 World Championship. important revolutions in their history. At the end of a decade in which electrification has progressively spread to all the major disciplines of international motorsport, the off-road world championship will also convert to hybrid propulsion, the characteristics of which have already been illustrated.
Starting in 2022, the WRC will see the new cars of the class as protagonists Rally 1, which differ from their progenitors in many respects, from the chassis to aerodynamics, passing through fuels with low environmental impact. By focusing on the motorization front only, the cars will keep the current 1.6-liter turbocharged thermal engines, capable of unleashing a maximum power of about 380 horsepower. The combustion engine will however be joined by a hybrid unit, which will be built by Compact Dynamics, which will then be responsible for the standard supply to all teams.
The WRC Rally 1 will therefore be equipped with the hybrid system known as P3, which encloses the electric motor, the control unit and the battery within a single casing, outlining a compact structure with an overall weight of 84 kg. The MGU electric motor generator, acronym for Motor Generator Unit, can therefore work both as an electric motor, delivering power to the wheels, and as a generator, exerting a braking action that converts the kinetic energy of the car into electrical energy that can be stored in the battery.
During acceleration, the MGU can work up to an engine speed of 12000 rpm and deliver a couple of 180 Nm, as well as a maximum power of 100 kW, equivalent to 134 horsepower, which added to those released by the thermal engine outline a maximum overall power of 517 horses, the advantages of which will be partially limited by the increase in the weight of the cars. Unlike in traction, the regenerative braking power is lower and limited to 30 kW. The motor generator will be mechanically coupled to the central transmission shaft, which is why the electric power will be distributed between all four driving wheels. A decoupling system will make it possible to disable the hybrid system in the event of technical problems, thus allowing the car to continue with the combustion engine alone, avoiding stopping in the event of faults in the hybrid part only.
The battery pack will be made by the affiliated company Kreisel Electric, which is already present in Rallycross and mainly manufactures batteries based on cylindrical lithium-ion cells. The batteries of the WRC 2022 will have a capacity of 3.9 kWh, the equivalent of approximately 14 MJ, and will operate at a nominal voltage of 750 Volts. Thus the battery pack and the entire P3 hybrid system will be contained in a single structure made of carbon fiber, designed to withstand impacts with decelerations up to 70 g.
The WRC Rally 1 will be plug-in hybrid cars and the batteries can therefore be recharged through external sources, with estimated times of around 20 minutes for a recharge from 20 to 80% of the total battery capacity. Where possible, the organizers’ objective is to recharge the cars with electricity produced exclusively from renewable sources, with the ambition of being able to implement this plan at least in European events. Given the wide diversity of contexts visited during the calendar, where there is no availability of renewable electricity, the batteries will be recharged with generators powered by biodiesel without fossil fuels. However, the long-term ambition is to replace these generators with hydrogen-powered ones, capable of producing electricity through fuel-cell technology.
Overall, the components of the P3 hybrid system will build on pre-existing technologies. The development led by the Compact Dynamics is mainly aimed at guaranteeing its reliability in the wide variety of scenarios faced by the cars of the World Championship. In fact, during the year we pass from the polar temperatures of the Swedish Rally to the climate of the Mediterranean stages or the trip to Africa, without neglecting the possible return of the event to Mexico located at high altitudes, which correspond to cooling problems linked to the rarefaction of the air.
Between mappings and modes
On the control front, the control unit will take care of the management of the electric power, which is why there will be no manual implementation of the hybrid by the driver or systems similar to push-to-pass. The control unit will automatically manage the hybrid system, adjusting the electric power according to the position of the accelerator pedal. In detail, there will be three different ways of controlling the hybrid:
- 100% electric mode (Full Electric Mode): this is a mode that can be used in particular situations such as transfers, during which the car is pushed entirely by the electric motor only limited to 50% of the power. In electric mode, an autonomy of 20 km is estimated calculated on the WLTC cycle aimed at reproducing the typical driving scenarios of urban and extra-urban roads.
- How to start the test (Stage Start Mode): at the start of each special stage, the hybrid system will deliver its 100 kW of maximum power to support the thermal engine for an interval of 10 seconds, during which an electrical energy consumption of 100 kJ is expected.
- Competition modalities (Stage Mode): can be used during special stages.
As for the race mode used during the special stages, the teams will in turn be able to develop three customized maps for the exploitation of the hybrid. Each mapping will correspond to a different aggressiveness in the delivery of electric power along the stroke of the accelerator pedal. The hybrid unit will therefore be pre-programmed to manage the power and energy available according to the length of the special test and the remaining battery charge. In the longer stages there will therefore be a frugal use of the hybrid system, while in the shorter special stages the contribution of the electric will be greater.
They will also be developed three different mappings for managing the braking contribution exerted by the electric motor generator, which in terms of sensations will be perceived by the riders like an engine brake. Each driver will thus be able to manage regenerative braking differently according to the behavior of the car preferred during deceleration. Regeneration under braking will be particularly important, as better regeneration equates to greater energy availability in the battery, making it possible to extend the usage time of the hybrid system. Furthermore, every time the driver presses the accelerator, the electric power will be supplied only if a minimum quantity of energy has been regenerated in the previous braking, renamed as Valid Regen.
While the attention of fans is catalyzed by the end of the 2021 season, on the other there is great interest in evaluating how the new generation of hybrid cars will affect handling. The pilots will in fact be asked to manage an increased power of over 100 horsepower, but at the same time they will have to quickly learn to manage the regeneration effectively to make the most of the potential of the hybrid system. The countdown to the Monte-Carlo Rally has begun.