The design tricks that could give Toyota a Rally1 edge

Roll back five years, few expected Toyota to come close to Hyundai, M-Sport, or Citroen on the World Rally Championship’s opening year of 2017 World Rally Car regulations. Two rounds in, the Yaris WRC had picked up its maiden win in the hands of Jari-Matti Latvala on Rally Sweden.

Two manufacturers’ and three drivers’ championships later, the Japanese marque has built a rock-solid reputation for building fearsome World Rally Cars.

Much of WRC’s pre-2022 focus has been on M-Sport’s testing head-start and its well-developed Ford Puma Rally1 design. It wasn’t until earlier this week that we were able to catch a glimpse of a Toyota Yaris looking like the Rally1 challenger that will line-up in Casino Square next month.

It doesn’t take long to realise, Toyota’s latest world championship contender follows the same downforce delivering philosophy of its WRC predecessors.

In this article, I’ll review five design areas I think Toyota will benefit from in 2022 and outline one feature that still looks less refined than its rivals.

1. Toyota GR Yaris Rally1

Finally, after a postponed 2021 introduction, Toyota will utilise the GR Yaris as its base model for the World Rally Championship. While marketing of Toyota’s performance hatchback remains a key influence, my question is: will Toyota witness a performance gain from the new shape?

From an initial look, I think it will. To be clear from the start, the switch to GR Yaris will only affect the bodywork. So when I talk about performance gains, I really mean aerodynamic improvements.

For 2022, stricter WRC regulations mean fans will see much less aerodynamic components on Rally1 cars. There are no winglets, no diffusers, and no arch vents.

This places even more importance on the base chassis that teams will use. The GR Yaris looks smooth, tightly packaged, and if you look at the rear of the car, there is barely any overhanging weight behind the rear axle.

As a result, Toyota will continue its theme of maximising aerodynamic performance. Both in terms of drag reduction which improves top speed capabilities, as well as guiding air flow to create optimum levels of downforce which improves cornering speed and acceleration.

The tightly packaged Toyota will also help its nimble and agile characteristics witnessed since 2017. The minimal bodywork at the rear of the car helps keep a low moment of inertia which again improves cornering abilities.

2. Rake and replicating a diffuser

If Toyota’s engineering department has got this right, they could really be onto a winner. Please bear with me on this one and take time to focus on Frederic Mangeant’s wonderful photo from Sebastien Ogier’s test day.

First, look at the inclination angle of Toyota’s side skirt and how the incline continues towards the rear bumper.

If you imagine a flat floor running across the bottom of the car at the same inclination angle. Well that is what gets me excited about Toyota’s GR Yaris Rally1 car.

Follow Formula 1 and you might run into the technical term “rake”. That is this front-rear inclination of the car’s floor.

Rally1 cars will suffer from the omission of diffusers in 2022. But what Toyota has managed with its design is something that comes as close as possible to a diffuser.

So, how does it work? Let’s start at the front of the car and work back.

Air will enter the underside of the Yaris below a tight gap between its front splitter and the road surface. This air flows under the car until it exits beneath the rear bumper.

Now, look at the profile of the Yaris’s floor between its two rear wheels. That angle of inclination maximises the area for the air to exist beneath the car.

If the same amount of air has a greater area to exist in, that region’s air pressure reduces. That in turn creates downforce, roughly in the area between the rear wheels, and generates more grip between the rear tyres and the road surface.

This concept is much more prevalent on Toyota’s design compared to M-Sport or Hyundai’s.

3. Rear cooling exits

Just above the bottom of the Yaris’s rear bumper is a set of cooling exits. In the centre, you can just about see fans which will help extract warm air from the battery pack area.

Beside the battery cooling exits is the exit for rear brake cooling ducts. Again, Toyota looks to have positioned these exits carefully to work together with the airflow exiting the underside of the car.

4. Rear wing

Toyota’s rear wing is, well, large. I’m not going to explain how a wing works but it is interesting to see how it aligns with the side mounted battery cooling inlets and front arches.

Keeping airflow laminar along the side of the Yaris is crucial to generate as much downforce from the rear wing as possible. The battery cooling inlets lie just below this path of air, meaning that it won’t impact the rear wing performance.

There are no side winglets on Toyota’s 2022 rear wing design, another change from the 2021 car. This could be required to meet new regulations or they may no longer be beneficial to have due to the position of battery cooling inlets.

The rear wing will be fed mainly by air flowing over the top of the car. The smooth shapes of the GR Yaris should help keep the airflow attached to the bodywork creating perfect conditions for the rear wing to work its downforce magic.

5. Side skirts

I remember reading an article by Toyota’s technical director, Tom Fowler, a few years ago. Speaking about the 2017 Toyota Yaris WRC, he explained how the side skirt design was taken to the very limit of WRC’s regulations.

Design to the millimetre is taken for granted in engineering and again this philosophy springs to mind when interrogating the GR Yaris Rally1.

As air flows along the side of the car, wide side skirts will reduce the amount of air interrupting the front-rear airflow underneath the car. Designers want to seal this airflow to encourage the downforce generated by the car’s rake.

The curvature of the side skirt leading onto the rear arch seems less aggressive than M-Sport’s equivalent. It just shows two different approaches to the challenge of encouraging downforce while avoiding the creation of drag.

6. Battery cooling inlets

One feature that still surprises me on Toyota’s Rally1 design is the battery cooling inlets. They seem big and a little cumbersome.

While the inlets are crucial to ensure batteries don’t overheat inside the car, they will also create a lot of drag, effectively slowing the car down as it pierces its way through the air.

Has Toyota played it safe to ensure reliability or is there another design change on the way before Monte-Carlo?

One possible explanation is the position of the battery cooling inlets. If designers have managed to flick air from the the front arches over the cooling inlets and onto the rear wing, then the bigger cooling inlets may not affect airflow too much.

Whatever the reason, it is going to be interesting to compare the three teams’ final designs on Rally Monte-Carlo.


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Thanks to Frederic Mangeant for supplying his excellent photos.

Adam Hall

Brought up in the Irish countryside, Adam was never far away from the world of rallying. From following local events like the Circuit of Ireland and the Ulster Rally, Adam now puts the stories from stages all around the world into words through his website Rally Insight.

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