Developing a hybrid transmission for the Hyundai i20 N Rally

In April 2021, Ricardo’s Performance Products team were appointed as a technical partner to support the Hyundai Motorsport team as it looked to challenge for the World Rally Championship title in 2022.

As experts in traditional, hybrid and fully electric motorsport applications, the team were tasked with developing an all-new hybrid four-wheel drive (4WD) transmission for Hyundai’s next generation of World Rally vehicles. Hyundai also renewed an existing agreement under which Ricardo supplies drivelines for its i20 N Rally2 car.

Required key characteristics of the new transmission would be to successfully integrate hybrid power into the driveline system, whilst maintaining and wherever possible seeking to improve, efficiency, performance, and driveability. 

The partnership was not the first time Ricardo has successfully worked with Hyundai. It follows an ongoing successful five-year collaboration, to develop a five-speed sequential gearbox and differential units, designed and manufactured in-house by Ricardo at its Midlands Technical Centre, in the Leamington in the UK.

As part of the deal, Ricardo drew on its extensive experience in the field of top tier, traditional and electric powered motorsport. Fundamental to the success of the project was Ricardo’s ability to remove the complexity from the driveline, control cost of production, and meet new regulations, which saw the removal of the centre differential and the banning of active differentials. Regulations also saw the removal of the semi-automatic (paddle shift) gear-shifting, which saw a return to a manually operated sequential shift gearbox.

Other changes included:

• A reduction of the ratios from six-speed to a five-speed gearbox
• Changes to the specification of casing wall thickness, and regulated amendments to minimum driveline weight, gear centre distance, gear widths among other key design parameters

Regulations specified by the governing body, the Federation International d’ Automobile (FIA) meant that design, manufacture and quality control were critical to prevent possible rule infringement – in addition to successfully integrating hybrid power into the driveline.

Ahead of the start of the 2022 Championship, all teams competing were supplied with a ‘standard’ e-kit from the FIA. The onus was then on the teams and their engineering and manufacturing partners to use design and engineering expertise to integrate new transmissions into the car, driving the rear axle.

The Ricardo team approached the task by incorporating a five-speed transmission mounted to a front (transverse) engine and a rear axle that features two main characteristics:

• A handbrake disconnect, which removes drive to the rear axle when the driver pulls the handbrakes to lock the rear wheels whilst still driving the front axle, and
• A hybrid drive arrangement, providing additional power on acceleration and from where regenerated power is returned to the e-kit battery under braking.

With transmission technology being limited by regulation, performance optimisation came from detailed design, differential configuration, microgeometry of gears and lubrication management. The transmission is also cased in aluminium to reduce weight and aid performance.

Steve Blevins of Ricardo said: “One of the most demanding aspects of the project was having to engineer a solution that not only met with the hybrid qualification, but that could also cope with extremes of temperatures and terrains and managing very high cases of stone strikes and jumps – all to a very tight timeframe 

“We’re delighted to have supported Hyundai Motorsport this season, and to have contributed to the success of their drivers, including two top three championship finishes for the drivers and second place in the manufacturers’ standings. We look forward to work to improve the capabilities and performance of the vehicle for the 2023 season.”