How the WRC’s hybrid boost will work

It's not a case of a power-boosting button, rather a technical process that makes Rally1 the most complex rally cars ever


In two weeks’ time, the new electrified era of the World Rally Championship will be firmly under way. Who will be leading? It’s impossible to say.

Which team will have done the best job? Again, DirtFish’s crystal ball isn’t powerful enough to bring you that answer.

But we can answer another key, lingering question ahead of the first event for the new Rally1 generation of WRC machines: How will the hybrid boost work?

Unless you’ve been living under a particularly large rock over the past 12 months, it won’t have escaped you that this year’s top class cars will feature a hybrid kit from Compact Dynamics that will generate up to 100kW of extra power.

But what’s less clear to those of us not working for Toyota, Hyundai or M-Sport Ford is precisely how this new system will be utilized throughout a WRC event.


Thankfully, during a conference call with select media including DirtFish, Toyota’s technical director Tom Fowler lifted the lid a little.

The first myth busted was the misconception that the extra power can only be enjoyed for a set period of seconds. Actually, as Fowler puts it, “it’s not actually a time-based strategy but an energy-based strategy that the FIA has implemented”.

“During braking, we have to regenerate a certain amount of energy in order to be able to deploy during the next acceleration, and the next acceleration has a limitation on the amount of energy you’re allowed to deploy during that acceleration which is relative to the length of the stage,” he explained.

“So in effect, the energy that you deploy should be such an amount that if you deploy on every section through the stage you equal your battery capacity at the end.

“It’s an energy-based strategy where you start with a full battery, you regenerate a certain amount and you deploy more than you regenerate and at the end your battery is finished.

Ogier test 4


Fowler explains the challenge of creating a brand-new hybrid rally car

“This is the FIA regulation in a nutshell.”

Hybrid is of course there to complement the same internal combustion engine that was used in World Rally Cars from 2017 to 2021. Rally1 cars will therefore be suitably rapid without the additional boost, but the surge of electricity will make for faster acceleration than ever seen in the WRC before.

It’s understood that plans are afoot to add hybrid boost usage to WRC TV’s regular graphics, so that viewers can see exactly when a driver is choosing to deploy extra power too.

That leads onto the next common question: how does a driver use their extra hybrid boost? As Fowler pointed out “the hybrid is active throughout the whole stage in the sense that it’s switched on, it’s regenerating every time you’re braking and it’s delivering torque for a proportion of every time you’re accelerating in theory”, but that doesn’t mean it’s always providing full power.

We’ll turn to M-Sport’s team principal Richard Millener, speaking to the press last summer, for added context on this one.

Millener M-Sport Sweden
It has to be integrated into the torque path so that you have a combination of internal combustion engine and electric motor combined into one torque which is linearized through the pedal map Richard Millener

“It’s not a button,” he said. “Effectively, the driver will have some help, or we’ll have some ability to choose when they deploy the hybrid, but it’s in short little bursts and it’s used constantly throughout the stage.

“The boost on the stages will be difficult to see externally where the hybrid is being used because it’s being used all the time.”

Fowler added: “During the braking phase they can regenerate, and when they reach a certain amount of energy they have like a boost ticket, let’s say, that’s available to them.

“Within the mapping of the car they have three different options for how the boost is coming and to put that into some context, one might be for ice and slippery gravel, one might be for reasonable traction gravel, and one might be for Tarmac.

“And then the torque which is coming from the electric motor has to be integrated into the torque request from the throttle pedal of the driver.

“So the driver is not allowed to have, for example, a separate switch to add boost or some indication of how the boost might come, it has to be integrated into the torque path so that you have a combination of internal combustion engine and electric motor combined into one torque which is linearized through the pedal map.

“And that’s the way it has to be deployed, so effectively if you have the boost available then you have a combination of engine and motor together and if you don’t then you have only the engine.”

Now we know more about how the boost can be deployed, how is it stopped? By hitting the brakes?

“That’s correct,” said Fowler. “During normal braking you’re regenerating but if you’re deploying during an acceleration phase and you touch the brakes then you’re required to stop deploying, in a similar way to if you touch the brakes when you have cruise control on on the freeway it might deactivate. It’s effectively the same situation.”

So there we are. Hopefully this provides a better understanding of how the hybrid system works in Rally1 cars.

But it’s worth remembering, this is the theory. In practice, might things be modified? Quite possibly, and there’s a bunch of experienced drivers that are all needing to get to grips with this new style of driving.