An engineer’s perspective on the “conundrum” of hybrid

Drivers expect hybrids to be a big benefit in México, but Toyota's Tom Fowler has some reservations


Tom Fowler’s not often undecided. He is now. Toyota’s technical director can’t make up his mind whether he’s comfortable with next week’s step into the unknown or not.

And make no mistake, Rally México is very much a step into the unknown for Rally1 cars.

The engineer in Fowler is railing against the lack of intel on what’s going to happen when hybrid hits previously untried and untested altitude of a mile and a half high with ambient temperatures potentially knocking on the door of 40 degrees.

But the adaptable adventurer in him is interested to have that ability for thinking on his feet tested.

“It’s definitely a double-edged sword,” Fowler told DirtFish. “It’s always nice to have some physical evidence that things are going to work, but it’s interesting to [have to] come up with counter measures for the lack of information. One side of the sword is frustrating, the other is interesting.”

In an effort to mitigate the lack of information, the teams completed their pre-México testing in Spain. The long-haul testing ban means crossing fingers in the hope of early spring sunshine. It doesn’t always work out like that.

“We got eight degrees,” said Fowler, dryly. “But we did get a good road that we think’s quite representative.”

As we know, the car’s power will be cut by as much as a quarter at the route’s highest point and that’s easy enough to replicate by winding the engine back.

So where’s the unknown?


This is the Rally1 car’s debut in México. Who knows what’s coming? Nobody. Literally nobody has done any physical testing to replicate this.

“That’s the biggest challenge,” said Fowler. “We’re taking a technical system we haven’t tested in these conditions, sticking it in the back of a rally car and driving it up a really high mountain. It’s a genuine unknown and a risk for the teams.

“There’s the conundrum of the reliability of the hybrid kit. So far we haven’t got every car through every rally without some sort of issue, so there’s no reason to believe we’re going to do that in México.”

Without doubt a hybrid failure will hurt more in México than anywhere else. A 10-second electrical burst of 134bhp is the same as sea level as it is at 2700 meters. That makes working hybrid an inordinately valuable and probably rally-winning commodity.

Typically, Fowler has drilled this one deeper and he’s ready to argue that altitude can, actually, impact on hybrid performance.

“It’s true that an electric motor doesn’t suffer in the same way an internal combustion engine would,” he said.

“But the altitude does impact on the cooling of the battery.”


The regulations stipulate that the hybrid parts have to remain within a temperature window and the thinner air will cause issues with that.

Fowler added: “We don’t know what the temperatures will be like in the car because we haven’t been there yet.

“We do know the altitude impact of México has been two-fold on the traditional ICE engine: the car is asthmatic because of the thinner air, but it’s also cooling itself with that thinner air and the two combine to reduce performance. The electric motor doesn’t need to breath oxygen but they do still need to cool themselves. Thinner air won’t cool as effectively and cooling is related to performance.”

Working with cooling partner Denso, Toyota has worked to gain as much insight as possible.

But next Friday, Fowler and the rest of the service park will hold it’s altitude-impacted thinner breath, watch and wait.

Words:David Evans