2026 Drama: Alleged engine loophole

[ME4ME]

Here is something interesting (and shady)!

This is C5.4.3. of regs, published July 31, 2025:
https://i.ibb.co/S4SdXptp/2025-07-31.jpg
As you can see, there is nothing about measuring at the ambient temperature.
Also 1.5 states that “Formula 1 Cars must comply with these regulations in their entirety at all times during a Competition”.
To me both of these together clearly say that the engine must not be designed to deliberately violate 16:1 compression rate rule, because why FIA can't come up with a measurement procedure somewhat close to operating conditions?

Now this one is Oct 16, 2025:
https://i.ibb.co/0pdtvvTK/2025-10-16.jpg
FIA added “executed at ambient temperature” and created that loophole basically at the last moment! Why did they do that?

Before I found out that I thought Merc did a good job exploiting that temperature trick and it’s not fair to punish them for being clever. But not anymore. Before Oct 16 their engine with compression rate 18:1 at high temperature was illegal. After Oct 16 changes it suddenly becomes legal! The only way I can think of this situation is that Merc knew in advance that their engine will become legal at the point in time when “it’s too late to change the engine” (or at least they had a backup plan), otherwise they would have never committed to something that is pretty clearly violates the regs.

Makes a lot of sense that engineers would question the FIA on the initial rule: Do we need to account for thermal expension and can you (the FIA) make sure all of our competitors are equally honest (in other words, how are you going to verify this?).

The FIA probably figured, fair enough, its a question worth asking, and proceeded with defining exactly where to draw the regulatory line: at ambient temperature.

Unless the FIA technical was staff totally naive, surely they must have known there would be some degree of freedom for manufacturers to exploit.

The 18:1 figure is BS, it's from the previous regs. Nobody knows what Mercedes, Red Bull Ford or any other manufacturer achieves with thermal trickery. The raceable CR might be just a little bit over 16:1 but the advantage is worth having.

This video is worth checking out at 02:38. It's an nice example of simplicity.


Obviously you can increase the "16" or decrease the "1" to achieve a ratio higher than 16. Practically you might need to alter both to achieve it. Using thermal expension and some sort of combination of material and geometry to manipulate volume in the cylinder throughout it's stroke a higher CR can be achieve. Lets say at racing temperatures you subtract 0.05 from both "16" and "1", you'd get 15.95 : 0.95 = 16.7895.

[Matt2725]

https://www.the-race.com/formula-1/ever ... ntroversy/

Article in The Race. Notably it states

Mercedes has been in dialogue with the FIA throughout the rules process so there is no element of it having tried to sneak something through.

It has had reassurance that its interpretation of the rules is in line with the FIA so it has kept pursuing its design process.

So suggestion there that the FIA were clued into what they were up to. Nothing was hidden from the regulatory body.

[ferkan]

Are they going back to 18:1? This is peak FIA/Tombazis

[dialtone]

Pure corruption mixed with bottomless incompetence.

Rules state 16:1 compression, but if you really want to run 18:1 it’s ok, just need to ask nicely.

[bluechris]

Are they going back to 18:1? This is peak FIA/Tombazis

And cripple the other manufacturers? That would be nice indeed for Toto but i don't think this is the case here. Very easy MB can stop the trick than the others to follow. 2014 vibes again?
They understand in FIA that the only people that will be left to watch F1 will be the Netflix ones and Toto followers?

[Mattchu]

Quack

Made my day

[Badger]

Pure corruption mixed with bottomless incompetence.

Rules state 16:1 compression, but if you really want to run 18:1 it’s ok, just need to ask nicely.

If we checked Ferrari's compression ratio at operating temperatures you think it would comply with 16:1?

[sucof]

As someone said perfectly:
The rule is the 16:1. The measurement is NOT the rule.

This sums it up all the dead end debate I think and it is impossible to challenge logically.


Additionally, it makes sense for the change of the wording regarding the measurements, that the question from Mercedes resulted the added "ambient temp" part, while they were working making themself safe... BUT this might caught other teams eyes, started thinking about the reasons and figured out what was Mercedes up to. Pretty logical as well. So Mercedes might have miscalculated their chess move with their question to the FIA.

But, overall I think the main problem is that the rules are not clear. It is not surprising Ross Brawn suceeded with the last rulebook having no or few grey areas, but he left before the current ruleset

[Matt2725]

Well allegedly the FIA agreed with Merc's interpretation of the regulations as per the article I linked above.

I don't know where they can go with this, at least this year. They told a PU manufacturer that the engine they had designed as legal. To pull that rug this late on would be arguably unfair and it leaves every regulation open to scrutiny about whether they're really ever a rule, or a suggestion until someone complains.

[catent]

Well allegedly the FIA agreed with Merc's interpretation of the regulations as per the article I linked above.

I don't know where they can go with this, at least this year. They told a PU manufacturer that the engine they had designed as legal. To pull that rug this late on would be arguably unfair and it leaves every regulation open to scrutiny about whether they're really ever a rule, or a suggestion until someone complains.

There is no evidence of a formal FIA ruling or binding approval, and the FIA does not pre-certify designs as permanently legal based on interpretation discussions. Article 1.4 places the burden of compliance squarely on the competitor at all times.

Unfairness has never prevented the FIA from enforcing or clarifying a regulation mid-cycle, nor should it. Allowing a potentially non-compliant design to stand because it is late would undermine the rules far more than enforcing the written limit.

Regulations are always subject to scrutiny; that is how F1 governance works. They are rules, not suggestions, and scrutiny is the mechanism by which they are upheld.

[vorticism]

We (and the press) could be interpreting this regulation change wrongly. It could be that performing the test at ambient temperature makes it more stringent. In which case this is the closure of a loophole, not the opening of one. If the supposed mechanism causes, for example, interference at ambient temperature then, for example, the piston might not be able to move or perform a full stroke which would be a red flag during the test. Said another way, it could be that heating the engine to operating temperature could make it easier to pass, hence the regulation change. High test mosport engines have well known warm up procedures. If the test involves moving the crankshaft through 360* while the engine is cold it could make the test more difficult in so far as would be demanding that all the moving parts cool down to a non-interference state. Just speculation. We don't know what the test entails, only that it measures GCR.

Nunes’ article suggested that it was the piston that was involved and that thermal expansion may not be the primary mechanism of action, rather that it could be a geometric peculiarity. If that is the case then I think I have a pretty good idea of what they might be doing as it reminds me of a concept I was working on a few years ago that I wanted to patent. I try not to post anything online that could have direct market value, though. I entertain myself with public domain stuff like motorsport sometimes, try to make sense of rumors. There's nothing to lose. Getting patents though is slow and expensive, and you only end up with something of dubious legal power within the most corrupt country on the planet, dealing with a judiciary that is either corrupt or, if you’re lucky, just inept. So I’ll let you guess where I’m at with patent applications. Innovation!

[sucof]

We (and the press) could be interpreting this regulation change wrongly. It could be that performing the test at ambient temperature makes it more stringent. In which case this is the closure of a loophole, not the opening of one. If the supposed mechanism causes, for example, interference at ambient temperature then, for example, the piston might not be able to move or perform a full stroke which would be a red flag during the test. Said another way, it could be that heating the engine to operating temperature could make it easier to pass, hence the regulation change. High test mosport engines have well known warm up procedures. If the test involves moving the crankshaft through 360* while the engine is cold it could make the test more difficult in so far as would be demanding that all the moving parts cool down to a non-interference state. Just speculation. We don't know what the test entails, only that it measures GCR.

Nunes’ article suggested that it was the piston that was involved and that thermal expansion may not be the primary mechanism of action, rather that it could be a geometric peculiarity. If that is the case then I think I have a pretty good idea of what they might be doing as it reminds me of a concept I was working on a few years ago that I wanted to patent. I try not to post anything online that could have direct market value, though. I entertain myself with public domain stuff like motorsport sometimes, try to make sense of rumors. There's nothing to lose. Getting patents though is slow and expensive, and you only end up with something of dubious legal power within the most corrupt country on the planet, dealing with a judiciary that is either corrupt or, if you’re lucky, just inept. So I’ll let you guess where I’m at with patent applications. Innovation!

Interesting thoughts on the matter and very cool you are working on such things! Good luck with your patent! (from a fellow inventor).

Reading your comment I remembered something, might be wrong: I have heard F1 engines have such design with small tolerances, that the engines crankshaft can not be even turned around when cold. It would either not be possible or would damage the engine! Is this true? If yes, then how would they measure compression ratio?
Or they have to warm up the engine as they do in the garage, then which will be the "ambient temperature", how the warmed up temp might differ between manufactures... etc...

[Bence]

Some say it's elegant engineering, not cheating. But at the moment the intention forms the thought "No. I take a different path." the entirety of the context automatically becomes cheating. The rule is the 16:1. If someone decides AGAINST it, he/she doesn't accept the RULE, therefore makes something illegal. Cheating. Fraud. Immoral. Call what you want.

And when the rules define that for example variable compression engines are prohibited/banned/not allowed (just to get used to the definition), AND the compression ratio MUST BE 16:1 MAX during the entire competition, then... you can't get that trained squirrel, my dear Veruca, no matter how intensely play the convulsively convincing egomaniac part of your playbook, cramping and screaming on the ground...

[vorticism]

Reading your comment I remembered something, might be wrong: I have heard F1 engines have such design with small tolerances, that the engines crankshaft can not be even turned around when cold. It would either not be possible or would damage the engine! Is this true? If yes, then how would they measure compression ratio?
Or they have to warm up the engine as they do in the garage, then which will be the "ambient temperature", how the warmed up temp might differ between manufactures... etc...

That's the question. How are they measuring it. Engine fully assembled? Disassembled to some degree? We won't know until someone posts the document online.

I've heard the siezed-when-cold claim as well; it's conceivable as there will always be a tolerance window to specify which takes into account thermal expansion, in terms of designing a cylinder bore. Regardless, that rumor was bandied about back in the NA era. Maybe back when they were using multiple engines per weekend. Unsafe-to-run however is different from saying the pistons are incapable of movement; so maybe it was lost in translation, exaggerated during the game of telephone. Maybe Tommy or grunt or wuzak will know.

[TeamKoolGreen]

So Red Bull tried to replicate the 18:1 compression ratio, after 7 months of trying failed and ONLY THEN decided to snitch on Mercedes