Updated on November 16th
FIA confirmed yesterday (November 15th) that “Rally1 cars will no longer use the existing plug-in hybrid units from next year”.
The FIA press release also announced that “from 2025, the minimum weight of Rally1 cars will be lowered from 1260 kilograms to 1180 kilograms and the air restrictor size reduced from 36mm to 35mm to maintain an equivalent power-to-weight ratio between the 2024 and 2025 vehicles”.
The possibility of a dehybridisation of Rally1 cars for 2025 announced last week by Autosport appeared to be confirmed when Hyundai fielded a non-hybrid Rally1 car at last weekend’s Rally La Nucía. Participation in the Spanish event was timed to keep the drivers in good shape for Rally Japan and to test the modifications the team is working on for 2025. And the fact that Neuville/Wydaeghe took part (and won) at the wheel of a non-hybrid car seemed to confirm what it has been finally announced by FIA.
T.Neuville/M.Wydaeghe, non-hybrid Hyundai i20 N rally1, 2024 Rally La Nucía test day – image by Javy Pérez Photografia
M-Sport already fielded a non-hybrid Puma Rally1 in three events this year (Poland and Chile for Sesks/Francis and Central Europe for Seideridis/Miclotte). However, the move into non-hybrid cars from 2025 is a very significant change, which will undoubtedly have an impact on the performance of a generation of cars designed to run hybrids.
The 2024 WRC Sporting Regulations already defined how a non-hybrid car had to be: replacement of the system by ballast (100kg) inside the car and removal of external air intakes and outlets, as well as rear radiators/fans. Now, most of this ballast will be removed (80 kg out of 100kg), which means that cars will be lighter, but also that the weight distribution will change. And the reduction in the air restrictor diameter (from 36mm to 35mm) will bring a reduction in the engine power, to keep a similar power-to-weight ratio between the 2024 and 2025 vehicles. The impact of a 1 mm reduction in the air restrictor will determine whether the cars of 2025 are the same, slower or faster than those of 2024. What is certain is that they will lose the extra boost during certain moments in the stages. Less power means more time required to reach high speeds. As we know, aerodynamics works better at higher speeds, so the delay in reaching high speeds will result in lower aerodynamic efficiency.
M.Sesks/R.Francis, non-hybrid Ford Puma Rally1, 2024 Rally Poland, 5th – image by M-Sport World Rally Team
Dehybridisation also means that no rear cooling circuit is required, and both side inlets and rear outlets can be removed. No side inlets means less drag and more downforce. Less drag due to the lower front area and the better drag coefficient (due to the more streamlined shape), and more downforce because the rear wing will receive a cleaner airflow. Intake removal will be especially beneficial for Hyundai. M-Sport was working on an improvement of the intake, as seen during recent pre-event tests.
Ford Puma Rally1 with a less prominent side air intake, 2024 Central European Rally pre-event test – extracted from Tom Nesrobvnal’s video
With a non-hybrid card, this modification is useless. Nor will Toyota benefit from it, which already removed the prominent side air intakes in 2023 and replaced them with a large hole, containing both the hybrid unit cooling and the rear brakes cooling intakes.
Detail of the (black) rear brake cooling intake in the 2022 Toyota GR Yaris Rally1 – image by Toyota Gazoo Racing WRT
While the side orifice is expected to be fully blocked in the non-hybrid car, we’ll probably see the return of the lower intake for brake cooling, as in 2022 (image above).
At the rear, the removal of the radiators, fans and outlets will bring some aero benefits, but also some drawbacks. Both M-Sport and Hyundai have blocked the outlets in the non-hybrid version of their cars, losing the benefits of having a forced air stream at the lower rear of the car.
T.Neuville/M.Wydaeghe, non-hybrid Hyundai i20 N rally1, 2024 Rally La Nucía test day – image by Javy Pérez Photografia
With some differences, all three hybrid cars used the air extracted by the rear fans to help remove air from under the car, thus reducing the pressure and generating downforce. The Hyundai seemed to be the most effective, with the two outlets located on either side of the exhaust pipe exit, to generate a curtain of energized air/gas to pull the air out of the bottom of the car, as shown in the image below.
A.Mikkelsen/T.Eriksen, Hyundai i20 N rally1, 2024 Rally La Nucía test day – image by Javy Pérez Photografia
With the blockage of the rear outlets, this benefit will be lost, and surely drivers will perceive a loss of rear grip. Toyota and M-Sport also benefited from this effect in their hybrid cars. But Toyota was already testing without rear fans, which means that dehybridisation of the GR Yaris Rally1 will have also a smaller impact at the rear of the car.
Toyota GR Yaris Rally1 (hybrid) without rear fans, 2024 Central European Rally pre-event test – image extracted from Rally fans Katovice video
In summary, drivers will have to get used to cars with less aero contribution, which means that the 2025 cars may become less effective and less spectacular, at least on some terrains. Which might be partially compensated by the reduction in weight and the final power-to-weight ratio.
The only precedent we have is the excellent performance of Neuville/Wydaeghe in La Nucía in a 2025-spec car, which we know now it was adapted to the new regulations approved yesterday. The Belgian duo was able to outpace Mikkelsen/Eriksen (in a 2024-spec car) by more than 45 seconds on a medium-speed, 128km-long tarmac. Will it be the same in 2025?
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