How much slower will Rally1 cars be without hybrid?

Toyota technical director Tom Fowler provides his insight on one of the big pre-2025 questions

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What’s the difference? New tires; no hybrid. Yes, but what’s the difference?

It’s the question you and I have been pondering since new Rally1 rules were confirmed at the end of last year.

Let’s start with what we know: hybrid’s gone and it’s taken its 10-second 130bhp-boost with it. No electric means no battery and a saving of around 100kg. The turbo’s air restrictor is reduced from 36 to 35mm and the whole thing is sitting on new boots: Pirelli’s gone, Hankook’s in town now.

What does that mean, when we tune in to the start of the Digne-les-Bains stage on Thursday what’s coming?

Toyota technical director Tom Fowler has crunched the numbers, dived into the deltas and done the sums. His thoughts?

“It’s very condition-specific,” is the slightly guarded response you’d expect from an engineer.

But he’s right. If the asphalt is bone-dry on the roads south-east of Sisteron, the cars will be slower on the D20 dash to the season’s first left-hander. The loss of 130 horses transmitted through soft, sticky slicks off a dry line will be telling. But if winter sits around that corner, the rest of the stage could be a different story.

As we know, massive power is only a good idea when you have massive traction.

So, let’s take the context of condition-specific and ask the question. What’s the difference?

“It’s not much,” Fowler offered, pausing for one more mental calculation. “It’s less than a second per kilometer. To the naked eye, the change will be fairly well invisible.”

There you have it. You and I, we’re hardly going to notice the difference. Even with their smaller restrictors, these cars will still be pushing out 400bhp and they’re still benefitting from the significant levels of aero grip generated from the splitters and wings.

I’ve advocated a move away from such high downforce cars and asked, in the name of spectacle, for the tires to be hardened with less grip. Cars moving is what we want to see. But is that the ultimate spectacle?

Fowler’s not convinced.

“From an engineer’s point of view,” he told DirtFish, “I don’t think there’s too much aero. I think there’s a school of thought that says that when you reduce the aero, you increase the spectacle. But I’m not sure that’s true.

“I think some of the most spectacular shots we have of Rally1 cars or 2017 cars are from the fast rallies, where the car is able to take sequences of corners at speeds which look unbelievable. And that basically comes from the aerodynamics, a lot of it comes from a normal car not being able to perform that sequence of corners at that speed. Obviously, the person steering it has a lot to do with it, but a lot of what we say is: ‘Wow, that Rally1 car was spectacular through there…’

“What Rally1 gives us at the moment and what WRC cars gave us before is this level of attraction where the top drivers are excited by the performance. I think we were at that stage clearly in 2020, 2021 at the end of that 2017-era of cars – the drivers were sad to see them go and maybe there was a small feeling that the heavier cars with hybrid was a backwards step [in performance terms]. When the discussion about taking hybrid out was brought to the drivers, they were like: “We want that power… but we want that level of performance.”

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Fowler doesn't expect this year's car to be much slower - partiuclarly to the naked eye

And dropping the minimum weight from 1260kg to 1180 will help deliver that performance.

Getting rid of the battery, motors and hybrid paraphernalia was, we were told, going to be a straightforward job. Is that the case?

“It’s been pretty straightforward, yeah,” said Fowler. “The new minimum weight gave us some work to do. It’s 80kg lighter, but with the pumps, coolers, fans and all of that weighed probably more around 100 kilos, so we’ve had to redistribute and repackage some of the weight in the car.”

And added ballast?

Talk of ballast can be a touchy subject with those in charge of developing the world’s fastest rally cars. It goes against everything they stand for, but fitting it to your car is something that can be worn as a badge of honor. Adding ballast means you’ve done your job in the lightening and balancing department.

“We had ballast in our car from the start of the hybrid era,” Fowler said.

The same can’t be said for all the cars which inhabited the service park through 2022.

Fowler: “The terminology that’s bandied around when you have new technical regulations is that it’s the same for everybody. Actually, that’s not quite true when the starting point is different and different cars have had varied levels of ballast.”

While converting a Rally1 Hybrid to a Rally1 might have been fairly straightforward, the implication of the change was significant in other areas.

“The change of regulations changed the whole development plan,” said Fowler. “As you can imagine, we had a trajectory to use our [homologation] jokers and to use our non-homologated parts where freedom is allowed to change.

“We had a plan that was spanning a five-year period that was based on a hybrid car. And the moment the hybrid unit was out, it had implications on that development plan. We had to redirect it to make sure anything we continue to do from that plan still has the same value as it had before and anything which wouldn’t bring value – because either it was directly or indirectly hybrid-related – is redirected to something more valuable with the new regulations in mind.

“Probably the biggest challenge is in rethinking that plan.”

With that in mind, what changes are bound for the 2025 GR Yaris Rally1 next week?

“I would say there are two main things that had to be done,” he added. “On the engine side, reducing the size of the restrictor from 36 to 35mm automatically has an implication on the ideal range in which to use your engine. What’s the torque compared to the horsepower? Effectively, torque [output] won’t change much, but there is less power. We’ve worked on that and we will come with an engine upgrade package for Monte Carlo which is now orientated towards the new regulation.

“The second change is in the transmission, with gear ratios and such like related to that engine performance. There’s no doubt, the change in work cost us time and wasted some energy – we were some way down the road with work on a 2025-spec hybrid car, but we’re happy with where we are at the start of the season.

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Visually, the GR Yaris Rally1 will no longer be sporting this slit in the rear bumper

“We know, for example, Hyundai is tied up with a lot of updates associated with suspension and transmission and this big package they’re putting together – this change in regulations could impact [Hyundai more].”

On the outside?

“The side view of the car hasn’t changed much,” said Fowler. “The cooling on the side of the car was doing work other than just [cooling] the battery. There’s still some inlets on the side, smaller than they were before, but we need it for the rear brakes and the rear transmission. From the back end, the rear bumper is now completely closed. So, where you could see the battery cooling fans and coolers and everything straight into the rear bumper, that’s all closed because there’s nothing in there anymore to extract from.

“I think we’ve done everything we wanted to do for this year. There will be changes coming as the season progresses, but for now we’re fairly happy.”

And fairly happy, as we know, is as good as it gets for an engineer.

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