Honda-powered cars have not only won the opening two rounds of the 2017 Verizon IndyCar Series, but have also heavily outnumbered Chevrolet-powered entrants in the top 12 in qualifying, 9-3 each time.

Rahal, competing for Rahal Letterman Lanigan Racing-Honda, told Motorsport.com: “I think what we’re seeing is a mentality change at Honda compared to this time last year. I think there was a very conservative mentality on the tuning side, the engine mapping, but now I think they’re pushing the boundaries. That’s probably why you’ve seen some failures, but at some point you’ve got to try and eke out every little bit.

“I think David Salters who joined HPD from the Ferrari Formula 1 team the winter before last is one of the key drivers there. Everyone at HPD has been responsible for the improvements, but I think he’s had a huge effect. From Day 1, he had the mentality of pushing the limits and they’re doing that and the engine is better, very strong.”

Chilton, whose Chip Ganassi Racing team switched from Chevrolet to Honda power for 2017, agreed, saying: “I was positive right away about the team switching to Honda. My first time trying [the HPD unit] wasn’t until January testing at Sebring, but all us drivers said how much bottom-end power the Honda had.

“It’s definitely the stronger engine to have and better on fuel economy, too. You could definitely argue it doesn’t have the same downforce level as the Chevrolet but you can’t argue with the results. [Honda] struggled last year to get cars in the Top 10 at the first two street races, and this year…. ok, we haven’t had pole positions but at Long Beach we had six Honda cars in the top seven. So they’ve made big gains over the winter.”

With aerokits having been frozen for 2017, Rahal said that remained the Honda weak spot, although the engine was helping compensate.

He said: “The road/street course aerokit is deficient – I think our new Honda partners at Ganassi could confirm that – and obviously we couldn’t change that for this year with the aero freeze. But at this point the engine is overcoming that to some extent with low- to mid-range punch.

“Then you can feel the drag kick in. On really long straights, like at Road America last year where we were third, I could see [Will] Power [Penske-Chevrolet] and [Tony] Kanaan [Ganassi-Chevrolet at that point] just take off from about halfway down the straights. It makes it easier for them to do the lap time.”

Chilton said that for him the main drawback with the HPD aero package was on the short ovals.

“Phoenix in testing was a lot more challenging for me than it was in my rookie year, when I thought we qualified and finished well for my first oval in IndyCar [started eighth, finished seventh].

“That’s going to be hard to repeat this year, I’d say. We haven’t got the downforce. I’m still not yet overly confident on ovals and when you feel like you haven’t got a car that’s as good as what you had before, it makes it a bit more challenging.”

However, Rahal said the recent tests at Indianapolis Motor Speedway, when James Hinchcliffe’s Schmidt Peterson Motorsport-Honda ran a 227mph lap, and the fastest Chevrolet car was on a 223, was “a complete joke.”

“On superspeedways, I think it’s very even between the two [manufacturers], honestly,” he said. “You have to be cautious about judging our engine rivals.

“That Indy test, we ran a 227mph but we ran qualifying boost at one point. And on the other side, we weren’t fully trimmed out because it was an awful windy today.

“But to believe they were 4 or 5mph off… Come on guys, we know better than that. No way. I’m not an idiot! Sandbagging is one thing but if you’re gonna do it, at least be close to what you’re really capable of.”