Let’s clarify the numbers: the current Formula 1 regulations allow an internal combustion engine compression ratio of 16:1 measured at ambient temperature. All power units checked in Australia were compliant with the 2026 technical regulations.
However, a heated controversy has been sparked by some F1 power unit manufacturers claiming that Mercedes, thanks to the introduction of a pre-chamber in the cylinder head, can reach 18:1 when hot, which is the value that was permitted until last year. There is no proof that the Brixworth unit can reach that limit, although the rumour has been fuelled by someone familiar with the project who moved to another team and “leaked” the concept. It is, however, accepted that it exceeds the 16:1 compression ratio.
After lengthy negotiations and considerable embarrassment for the FIA, whose technical commissioner responsible for power units, Vincent Pereme, had declared the Mercedes power unit legal, a unanimous agreement was reached among the engine manufacturers gathered in the PUAC (Power Unit Advisory Committee) to modify Article C5.4.3, which governs the power unit compression ratio.
The new wording states:
No cylinder, as referred to by C5.1.3, of the Engine may have a geometric compression ratio higher than 16.0, measured in the following conditions:
Until 31 May 2026: when the Engine is at ambient temperature
From 1 June 2026 to 31 December 2026: when the Engine is at ambient temperature as well as when the Engine is at 130degC. Any component, assembly, mechanism, or integrated arrangement of components that is designed or functions to increase the compression ratio in operating conditions beyond 16.0 is prohibited.
Toto Wolff maintains that the Mercedes power unit complies
Photo by: Sam Bloxham / LAT Images via Getty Images
But what does this mean?
Let’s try to understand the effects of these provisions, because some data has not been made public and has not been fully clarified. From June 1, therefore, the verification parameters will change. Nowhere has it been stated, for example, that in the agreements reached, a tolerance in the compression-ratio measurement was introduced that pushes the maximum allowed value to 16.7:1, to be measured at 130°C. One clarification is also worth adding: we are talking about the oil temperature in the six-cylinder engine.
It is worth remembering that Audi and Porsche, during the drafting of the power-unit rules, were the ones who requested a 16:1 compression ratio. Where Mercedes can actually reach is objectively unknown, just as it is unknown whether the current engine will comply from June 1. According to the three-pointed star, no intervention will be needed, while those on the other side of the barricade claim that it will have to modify the cylinder head, perhaps widening the small hole that, with its current diameter, prevents the pre-chamber from filling at high temperatures.
One thing is certain: the early-June date is not random. Initially it seemed the measure would come into force in August, not at the start of summer. Why? The answer is simple: we must link the measure to the calendar. Teams have three power units for 24 Grands Prix, so each unit should theoretically last eight events.
And which would be the eighth race? The Monaco Grand Prix, scheduled for June 7. Mercedes, therefore, if it has to intervene on the V6, could introduce modifications on the second engine, which would be introduced around then providing reliability is up to scratch.
Since the Petronas sustainable fuel was designed to exploit the calorific potential that can be extracted from a higher compression ratio, it is reasonable to think that a less aggressive fuel could also appear in the new configuration.
Audi was one team that pushed for the 16:1 compression ratio
Photo by: Joe Portlock / Getty Images
Rivals, meanwhile, might resort to the Additional Development and Upgrade Opportunities (ADUO) system in an attempt to reduce the performance gap to the power unit designed by Hywel Thomas and the team at Mercedes High Performance Powertrains. An update to the six-cylinder engine alone can be requested after the sixth race, the Miami Grand Prix – depending on the fate of F1’s races in the Bahrain and Saudi Arabia. The FIA can authorise engine changes (with additional budget outside the cost cap) if a 2% lower power output emerges compared to the reference engine (Mercedes).
The modification could be approved at the 12th race (Belgian Grand Prix) and might become operational from the following race, the Hungarian Grand Prix on July 26.
It is therefore natural that Mercedes boss Toto Wolff identifies Ferrari as the real major challenger: he certainly praises the qualities of his power unit, but he also hopes to bank points early and attempt an immediate championship breakaway, keeping the Scuderia close behind while avoiding, perhaps, the eight-tenths advantage inflicted on rivals in qualifying.
Especially since McLaren, despite using the same Mercedes engine, has not yet “understood” the perfect management of the power unit’s energy recharge, and is currently chasing the Silver Arrows while feeling the effects of being a customer team. The Woking team will not take long to figure out what to do in order to re-emerge as a dangerous rival. But it will take some time.
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Disclaimer : This story is auto aggregated by a computer programme and has not been created or edited by DOWNTHENEWS. Publisher: motorsport.com
