Why drivers are turning their hybrid units off

Takamoto Katsuta and Elfyn Evans were just two drivers to disengage the system in Croatia, but why?


Turn. It. Up. For those fortunate enough to remember Formula 1 in the ’80s, those three words will forever mean one engine, one purpose and a single qualifying lap with a right foot tickling 1400 horses.

Hybrid has delivered something of a ‘turn it up’ attitude to the World Rally Championship with a full battery’s worth or boost slinging another 130-odd brake horsepower in the driver’s direction. But it’s not always welcome.

In Croatia last month, it wasn’t so much a case of ‘turn it up’ as ‘turn it off.’

When the fog, the mist, the rain and the general misery arrived on SS11 and on the penultimate stage of the Zagreb-based event, Elfyn Evans and Takamoto Katsuta were just two of the drivers who took the decision to pull the plug on the electrics.


Close to 400bhp on the wrong tires was more than enough for the GR Yaris-driving pair – neither of whom were in any kind of a battle.

But what does flicking the switch and killing the hybrid boost actually mean?

Toyota’s technical director Tom Fowler explains the process – which is literally completed by the flick of a switch – is about more than just restricting the amount of power being fired at four wheels.

“We have the three levels of mapping you know about from the regulations,” he told DirtFish. “Let’s say high power, medium power, low power [from the hybrid] and at some point you have a grip level where even the combustion engine is enough or even too much – that was the case in Croatia.

I think there will be times when we could see cars in the lead fight turning the hybrid off Tom Fowler

“Don’t forget, even with the combustion engine we have different calibrations which allow for the power to be turned down to a lower level for very slippery conditions.

“The wheelspin, the traction and the car behavior is a big part of the decision to turn it off. But I think the biggest reason why Taka turned it off, particularly on this occasion, was that the hybrid system is requiring you to do a certain amount of braking before you can regenerate and reboost again.

“There’s a strategy which dictates where he has to boost and not boost – it’s something else to think about and another process to go through.

“In SS11, I think, the biggest part of it was not necessarily the car’s handling characteristics but the thinking: ‘if I turn it off, I will have enough power and I’ll have one less thing to think about.’”


Watching those in the fight try to manhandle 500-plus horsepower through some of the most compromised conditions in years was spellbinding. But was it the fastest way?

“I think there will be times when we could see cars in the lead fight turning the hybrid off,” said Fowler.

“But the conditions will have to be pretty terrible, with massively limited levels of grip. It’s very rare for drivers to be talking in terms of less power.

“They’re more about turning it up rather than turning it off.”

Words:David Evans