The debate centres on the mandated reduction in compression ratio from 18:1 to 16:1 for the new power units, and whether the regulations adequately account for what happens once engines are running at operating temperature.
While the rules specify that measurements are taken when the engine is stationary and at ambient conditions, rivals believe some manufacturers may be exploiting thermal expansion to achieve a higher effective compression ratio on track.
Speaking at Audi’s 2026 car launch, technical director James Key said the issue strikes at the heart of fairness under a homologated formula.
“We have to, as we do, trust the FIA with making the right decisions here,” Key said.
“It’s new regs. You’ve got to have a level playing field. If someone came up with a clever diffuser and you said it’s not the right thing to do, no one else can have it, but you can have it for the rest of the year.
“It doesn’t make sense. We’d never accept that.”
Key’s comments echoed past regulation flashpoints, notably the double-diffuser controversy of 2009, when wording loopholes created advantages that rivals could not realistically copy mid-season.
With 2026 power units tightly homologated and operating under a cost cap, teams fear a similar scenario where any perceived grey-area gain becomes effectively untouchable.
“I think if it’s sort of bypassing the intent of the regulations, then it has to be in some way controlled,” Key added.
“So we trust the FIA to do that, because no one wants to sit a season out if you’ve got a blatant advantage that you can do nothing with in a homologated power unit.
“So I think for us, hopefully, the FIA will make the right decisions.”
Audi’s stance aligns it with Ferrari and Honda, who are understood to have queried whether the compression ratio should be considered a hard limit at all times, rather than only under static checks.
Honda Racing Corporation president Koji Watanabe acknowledged the regulations leave room for interpretation, while CEO Toshihiro Mibe said manufacturers are seeking clarification from the FIA on which concepts are acceptable.
“Regulations do not have everything listed very clearly, bit by bit,” Mibe said.
“So in the new regulation, we look into the possibility of the new technology for each of the different power units.
“There is a lot of room for interpretation as well, and this is a part of the race. So for the FIA, it’s up to them to decide on whether it’s good or bad.”
On the other side of the debate, Mercedes and Red Bull Ford Powertrains have played down suggestions that anything improper is taking place, with both widely reported to be among the manufacturers thought to be gaining an advantage from the situation.
Red Bull engine chief Ben Hodgkinson has repeatedly insisted the controversy is being overblown.
“I know what we’re doing, and I’m confident that what we’re doing is legal,” Hodgkinson said.
“Of course, we’ve taken it right to the very limit of what the regulations allow. I’d be surprised if everyone hasn’t done that.
“My honest feeling is that it’s a lot of noise about nothing.”
Hodgkinson pointed to the regulations themselves, which define compression ratio checks at ambient temperature, while acknowledging that all manufacturers inevitably push thermal efficiency to the maximum.
The FIA has so far resisted any immediate intervention, stressing there is no evidence of wrongdoing and that the matter is being handled through technical forums rather than protests.
A meeting involving all five 2026 power unit suppliers — Mercedes, Red Bull-Ford, Ferrari, Honda and Audi — is scheduled for Thursday, with dynamic measurement methods among the topics expected to be discussed.
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