#engine regulations

There are two compression ratios, for every engine that uses or generates heat as part of its compressive function: - Static compression ratio: the amount a fuel can be compressed in ambient conditions. - Dynamic compression ratio: the amount a fuel can be compressed in the engine's running condition. The regulations in F1 clearly stated that engine compression are measured at ambient conditions. This means it is static compression ratio, not dynamic compression ratio, that is being regulated. "Ambient" means the prevailing weather conditions at a venue at the moment the measurement is taken. We know this partly because the term "ambient" is also used to determine what temperature fuel is allowed to be when stored on competition days. At one point, it could not be stored at less than 10 C below ambient (it is now required to be stored at ambient). If "ambient" meant "running condition", then keeping fuel at 10 C below that would cause it to spontaneously combust every day. Hello pit lane fires… All engines must comply, even if the day is hotter than expected. If there was a race weekend at 62 degrees C this year, the engines would have had to be compliant with the static compression ratio. This applies even if the drivers didn't drive for heatstroke risk - if cars are presented for a session, then the ambient of that moment is the one that is used. The fact it's higher than the teams anticipated is not considered a defence. Even static compression has a loophole. Greater static compression is possible at cold races than hot ones. If something in the engine raises the static compression ratio when the ambient temperature falls, this would allow the engine to run faster at colder races. In practise, this is physically less likely than the proposed ability to increase dynamic compression ratio, because materials expand when heated. Bimetallic strips that turn off kettles when water boils have worked that way for decades - so the issue is actually controlling the increase in dynamic compression ratio at high temperature. Uncontrolled increases are trivial - increases while controlling for unwanted vibrations, power inconsistencies and engine damage are the real trick. The secondary requirements needed to control these side effects of very high dynamic compression is why teams have generally shied away from deliberately employing it. The most likely reason the FIA used wording that locked the definition of "compression ratio" to static rather than dynamic is enforcement. Static compression can be measured by one person with basic measuring equipment, any time the car is in parc fermé and has not been running for about an hour. This is easily arranged at every single race, as well as at initial Thursday scrutineering. (The only reason it doesn't get done every race is because the full regulations are about as thick as a biscuit tin, or maybe a large jewellery box). Dynamic compression ratio is much trickier to enforce. That makes the originally-mooted scenario of "just" taking out Mercedes look wonderful in comparison. There's also the point that the way the regulations are written now, if the rule is changed to mean dynamic compression ratio, there would no longer be anything covering the static compression ratio, leaving a whole new bunch of loopholes for the taking. Also, if the dynamic compression ratio is made 16:1, given no F1 engine's running temperature can possibly be every venue's ambient, and the manufacturers have been building static compression ratios of 16:1, then every single one will fall at Melbourne. Every single one. That's simply physics. Remember, the only thing Mercedes was "getting away with" was following the regulations as written and as reasonable to interpret by anyone who understood what an engine compression ratio was in the first place. The FIA has just told everyone that only telepathy or cheating is allowed - and none of the teams or engine manufacturers has a telepath on the staff.

At the moment, no opportunity to change the engine has been provided, except to engines more than 2% behind the lead engine. It takes 100 days to change an engine design in the throughgoing way this requires (we know this because of an engine change Force India had to do before the 2009 season), so any engine wouldn't be ready until June at the earliest. The test then has to be taken and complied with, and only then can it be put on the car. So there would need to be a regulation change before this could be implemented. Oh, and the specified change is 3 July (i.e. Silverstone weekend), not 1 August. Also, as I will emphasise again, winning would have been the FIA complying with the regulations it set out, instead of breaking them by deliberately and knowingly changing the regulations in a way that prevented engines legal when the design process started from being raced. We still run a high risk of F1 not getting to Silverstone - unless it turns out that everyone was already compliant, which would mean that the FIA formally establishing the precedent that it can cheat against a specific competitor whenever it likes will be set, for no reason at all. Hence, Mercedes was on the side that won but still hasn't won.

The basic regulation has been in the rules since 16 August 2022 (the first issue of the 2026 regulations. Please check fia.com, Sport -> World Championships -> FIA Formula 1 World Championship -> 2026 Regulations -> Archives -> 2026 -> Section C (8 August 2022), Article 5.6.3 of the Technical Regulations, which specifies the test will be in the Appendix. Interestingly, the Appendix doesn't list the test, even though the dangling reference in Article 5.6.3 exists. Indeed, that was still the case on the Section C of 24 June 2024. However, this reflected the situation in the then-current regulations (2022-spec), which were in fact looking at compression ratio (albeit looking for 18:1 instead of 16:1). The Technical Regulations also state that undefined terms will be in Issue 12 of the 2022 Technical Regulations. All that says on the subject is Article 5.4.6's "No cylinder of the engine may have a geometric compression ratio higher than 18.0". Only… this version talks about "geometric ratio". It turns out that there's a generally understood method for how to measure this: Grassroots Motorsports demonstrates how to measure engine compression in a motorsport engine . The method described is clearly a static compression ratio measurement at ambient temperature. I also include descriptions of the method from x-engineer and a description from Group K about why measurements done at temperature (i.e. dynamic compression ratios) are generally not taken seriously (which matters when making it an enforcement regulation, hence why the FIA didn't do dynamic compression ratio measurement in any iteration of the regulations prior to the engine manufacturer vote). So what we have is the FIA not only not specifying a temperature, but using a definition that would generally be understood to mean ambient environmental temperature (i.e. the definition I used in my first response to anon on this topic). All engines run a higher dynamic than static compression ratio. That's physics. At that point, any reasonable motorsport engineer would have understood the regulation as specifically and intentionally covering ambient and not running temperature. That is the regular, common-sense definition of the regulation. (There are perfectly valid engineering reasons why exploitation of this fact has previously been, and apparently continues to be, limited in F1. However, sportscars have experimented more with it over the decades, something the FIA of all organisations should have known perfectly well). Whether the FIA and the non-Mercedes engine manufacturers like it or not.

Psuedopolitics in general are definitely happening. This is generally the case when good-faith interpretations of regulations, or rumoured high-tech solutions are being opposed. (An excellent book about this is Ross Brawn and Adam Parr's Total Competition, which riffs off Sun Tzu's The Art of War to explain, among other things, how the technical and psuedopolitical aspects of F1 interacted in the 2000s). I don't work for the FIA or Mercedes (having the odd contact with links to F1, and… previous with the FIA, isn't the same). The ridiculous thing is that this is one issue where it should be possible to disclose the basics of the psuedopolitical issue (if not the technical one), but there's been a distinct lack of interest. A good clue is the Pat Symonds article about the controversy in Autosport's March 2026 edition. Pat was on the committee that decided the 2022 regulations, and helped with the first draft of the 2026 regulations (it was re-drafted after he left the FIA). He was invited to that committee after decades of being a top F1 engineer who had demonstrated understanding of how the whole car worked together. He should, therefore, understand that the difference between static and dynamic compression was shown in the regulations as existed in 2022 and the first 2026 draft, that these would affect the engine manufacturers' behaviour (regardless of stance towards interpretation) and that his audience, readers of a magazine aimed at general motorsport fans, might appreciate a quick reminder of all this. Maybe even an explanation of the fact two compression ratios exist in the first place. None of this happened. There is an explanation of what a compression ratio is. There is a an explanation of temperature. At no point are these two explanations connected. This meant that Pat ended up claiming the FIA do not accept Mercedes' explanation, while making it look like the FIA didn't have a leg to stand on in acting at all. Neither is true. The FIA hasn't assessed Mercedes' explanation at all, it is simply voting for something without thinking through the consequences, and then enacting the vote in a thoughtless way. The FIA may not have a very good case, but it is perfectly at liberty to draft a ruleset that meets its intentions better, set a reasonable deadline by which its vision of compliance is met and mete out consequences at *that* point if anyone is not in compliance with the new version. Pat presented the FIA as whinging because it deliberately misinterpreted a regulation that has had an obvious and well-known definition for many years, despite being one of the people who drafted that regulation. (If you'd written that piece, assuming you weren't known to have literally drafted any of the 2022 or 2026 regulations, I would have read less into it. The ring of hypocrisy wouldn't be there). This itself suggests what sort of psuedopolitics is going on. It indicates the FIA itself is using the occasion for psuedopolitics (rather than its alleged job of regulating the series). The engine manufacturers may also be psuedopoliticing, but when the organisation meant to set an example of *not* engaging in it does so, it's hard for other players in F1 to resist… (PS: I need to update part of my response to one of your other asks, thanks to information in the Symonds column).

Unfortunately, the FIA hasn't left itself space to do that. It changed the regulations by pressuring the other engine manufacturers and Liberty. It is now legally required to enforce the regulation or back down completely, citing the interests of the sport. No compromise position is available for it to inhabit (at least not without breaking the FIA's own Statutes about complying with its own democratic processes). We do not know if Mercedes is attempting the dynamic compression ratio, or whether it refused to go with the others out of respect for the continued existence of F1 (or a third reason). The issue is that the FIA has forced a battle where the only options are that it backs down, nobody gets disqualified (so everyone looks like they created a controversy over nothing, the exact opposite of the FIA's claim) - or F1 ceases to be able to comply with its legal obligations.

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