Vote set for proposed change to F1 compression ratio tests

The FIA has proposed a new approach to the way it tests for compression ratio limits, with Formula 1's power unit manufacturers to vote on whether to approve a mid-season change that could hamper Mercedes.

The Mercedes power unit has been the center of discussion through the off-season over reports it has developed a piston design that allows it to measure within the 16:1 compression ratio limit at ambient temperatures but exceed it – closer to last year’s limit of 18:1 – when running. Such a design would allow greater power unit performance, although Mercedes team principal Toto Wolff has downplayed the impact of such a difference.

With Mercedes regularly stating its design is legal, rivals have questioned whether it meets the intent of the regulations, and the FIA has now opened up a vote to make a change.

Rather than testing at ambient temperatures, the governing body proposes it can also do so at a representative operating temperature, in a change that would be brought in from the Dutch Grand Prix – after F1's summer break – if approved.

“Over recent weeks and months, the FIA and the Power Unit Manufacturers have collaboratively developed a methodology to quantify how the compression ratio changes from ambient to operating conditions,” the FIA said in a statement. “Following validation of this approach, a proposal has been submitted whereby, from 1 August 2026, compliance with the compression ratio limit must be demonstrated not only at ambient conditions, but also at a representative operating temperature of 130°C.”

The FIA expects a result of the e-vote to be received within the next 10 days, ensuring clarity will be provided before the first race weekend of the season in Australia on March 6-8. Any change would still need to be approved by the World Motor Sport Council.

Last week, Wolff said his power unit department would have to accept if changes were made.

“There is a governance process, and if that governance were to vote for an engine regulation change, you just have to take it on the chin,” Wolff said. “It is what it is. And obviously in that case, it would be detrimental for all of the Mercedes power teams.”