© Mercedes-Benz Group AG
The FIA has proposed a solution to Mercedes’ power unit compression ratios issue, and announced that F1’s power unit manufacturers are set to vote on it.
The biggest controversy that emerged at the beginning of 2026, has centred around the legality of Mercedes’ new power unit.
More specifically, rival F1 teams have accused Mercedes and Red Bull of having found a way of getting around ‘compression ratio limits’, as described in the new regulations.
This has to do with how much the air-fuel mix in an engine is compressed prior to ignition. In the new regulations, the limit has been dropped from 18:1 to 16:1, to improve sustainability, and this ratio is measured when the engine is off at ambient temperature.
Since a higher ratio equals more power, it is implied that Mercedes and Red Bull have found a way to increase the ratio by using materials that expand at higher temperatures (temperatures achieved while the car is racing on the track). As already explained, the FIA’s current measuring methods do not measure the ratio in these conditions.
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Rival teams believe this ‘trick’ should be made illegal by amending the regulations. Surprisingly, even Red Bull has joined those who are calling for the regulations to be changed.
The FIA has now come out with a possible solution to the issue that will be put to a vote through the relevant Power Unit Advisory Committee (consisting of F1 power unit manufacturers, the FIA and Formula One Management).
The proposed solution is to introduce additional hot tests for the power units over the summer break, more specifically a mandatory test at 130 degrees to be introduced from August 1 2026.
This would allow Mercedes to make necessary changes to their power unit. Alternatively, the tests would not be introduced until the 2027 season.
Motorsport.com reports that the five power unit manufacturers have been given a 10-day period to vote on this online. The FIA and Formula One Management will also cast their votes, and a supermajority of four manufacturers plus the two bodies is needed for the change to be voted through.
“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 statement read.
“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 vote has been submitted to the Power Unit Manufacturers, and its outcome is expected within the next 10 days and will be communicated in due course.
“As with all Formula 1 regulatory changes, any amendment remains subject to final approval by the FIA World Motor Sport Council,” the FIA concluded.
