2026 Drama: Alleged engine loophole

[Rodak]

There are significant issues with doing a hot test. Unless there is a simple thermal valve that opens/closes according to temperature (or pressure) as it is the interaction of the various thermal expansions/contractions at operating speed, which cannot be modelled on a stripped engine.
As far as I am aware there is only one way to prove the non-swept volume in an ICE and that is measuring the fluid volume in each half of the cylinder (head & block) and the volume created between the two by whatever gasket/seal is used between the two.
You also need to randomise the tests to accommodate tolerances.

These ICE’s are massively boosted, so a cylinder pressure limitation would be a better metric for a limitation.

The cylinder pressure limit is 4bar.

Totally agree with Stu, good comment. As to 'cylinder pressure limit is 4 bar', no it isn't. Boost pressure is limited, not cylinder pressure. From the 2026 Technical Regulations:

5.5.2 Engine intake air pressure must be less than 4.8 barA at all times. The pressure of the air will
be measured by two FIA approved and sealed devices through which all air destined for
combustion must flow. These devices must be installed in FIA approved locations situated in
the engine intake air system downstream of the charge air cooling system (as described in
Article 5.25.2)

[SB15]

I don't know why there is so much controversy, to me I believe that Mercedes can easily switch to a 16:0 if they needed to.

Now, is that their only "advantage"? No! It seems to me that the teams are fearful of how capable that W17 will be on track because while yeah an engine advantage may help, but that's not the only part of the car that determines your title chances.

Merc themselves reported that the car was better than the simulations were saying and both drivers reported it felt far better to drive than previous years regardless of the engine.

But we'll see the decision (conclusion) from FOM and the FIA

[pantherxxx]

I don't know why there is so much controversy, to me I believe that Mercedes can easily switch to a 16:0 if they needed to.

Now, is that their only "advantage"? No! It seems to me that the teams are fearful of how capable that W17 will be on track because while yeah an engine advantage may help, but that's not the only part of the car that determines your title chances.

Merc themselves reported that the car was better than the simulations were saying and both drivers reported it felt far better to drive than previous years regardless of the engine.

But we'll see the decision (conclusion) from FOM and the FIA

I wouldn’t be surprised if the correlation between wind tunnel data and real world is much better for all teams compared to last year. Ground-effect cars, with their large venturi tunnels, make accurate correlation far more difficult, so this likely isn’t unique to Mercedes.

[AR3-GP]

Autoracer is now reporting the 2nd combustion chamber theory...

[Stu]

Can we start calling it the “ante-chamber”?

[Sergej]

Autoracer is now reporting the 2nd combustion chamber theory...

Don't believe everything you read on the internet.

[upsidedowntoast]

Autoracer is now reporting the 2nd combustion chamber theory...

It's weird because I remember exactly where this misinfo came about in the first place:
https://www.auto-motor-und-sport.de/for ... orentrick/

They proposed it as a devil's advocate theory and then in the next sentence went on to say "no, that would have been shot down as illegal immediately".

Yet now a ton of people are latching on to that as fact. Including other outlets I guess. Same as with "Red Bull switching sides" -- the original source of that was the Italian newspaper saying "Red Bull is *open* to switching sides" and by the very next day people are acting like they already have / that they were the ones who leaked the news to the rest of the teams because they couldn't get it to work. We still don't know if Red Bull did or didn't get the trick to work.

What we do know is that 1) the rumors of the Mercedes trick was already circulating as early as the middle of last year, 2) during that same time Red Bull was already rumored to have it too, and 3) the FIA has acknowledged some kind of temperature-based compression ratio trick but no other details, whether it's thermal expansion of metals, negative thermal expansion, antechambers, curved chambers, etc.

Everyone is just citing soundbites from one another without verification or fact checking I guess.

[Sergej]

Genuine question: if a second chamber existed, wouldn't it be visible from CAD models ? wouldn't FIA say straight away "ehi Mercedes, wtf are you doing?"

[f1isgood]

Genuine question: if a second chamber existed, wouldn't it be visible from CAD models ? wouldn't FIA say straight away "ehi Mercedes, wtf are you doing?"

I think there may be other ways to justify it potentially. Maybe the FIA did not see it as a big threat/issue. If it's just a chamber, Mercedes can simply "close" the chamber as well.

[Luscion]

Autoracer is now reporting the 2nd combustion chamber theory...

Don't believe everything you read on the internet.

its more so them coming up with ideas on how the compression ratio trick would work and how a possible second chamber would work, their conculsion is that a second chamber would be so into the grey area it would be illegal

[f1isgood]

Autoracer is now reporting the 2nd combustion chamber theory...

It's weird because I remember exactly where this misinfo came about in the first place:
https://www.auto-motor-und-sport.de/for ... orentrick/

They proposed it as a devil's advocate theory and then in the next sentence went on to say "no, that would have been shot down as illegal immediately".

Yet now a ton of people are latching on to that as fact. Including other outlets I guess. Same as with "Red Bull switching sides" -- the original source of that was the Italian newspaper saying "Red Bull is *open* to switching sides" and by the very next day people are acting like they already have / that they were the ones who leaked the news to the rest of the teams because they couldn't get it to work. We still don't know if Red Bull did or didn't get the trick to work.

What we do know is that 1) the rumors of the Mercedes trick was already circulating as early as the middle of last year, 2) during that same time Red Bull was already rumored to have it too, and 3) the FIA has acknowledged some kind of temperature-based compression ratio trick but no other details, whether it's thermal expansion of metals, negative thermal expansion, antechambers, curved chambers, etc.

Everyone is just citing soundbites from one another without verification or fact checking I guess.

Newey said that except for one manufacturer everyone is on board. At this point, the reality is Mercedes is on one side and others on the other. While the details of the rumors might be nonsensical, the rumors themselves are true -- Mercedes potentially is doing something that others dislike.

[chrstphrln]

Well, this is the issue. Unfortunately Toto is correct: “The power unit is legal. The power unit corresponds to how the regulations are written. The power unit corresponds to how the checks are being done.”
This is the truth that too many here try to somehow not see. The CR is measured at ambient. Period. How much it is when the engine is running does not play any role in the current rules.

No, Toto is still talking nonsense.
He's quite aggressively claiming his engine complies with the rules because it passes the test.

He's conflating two completely unrelated things, and he knows it perfectly well, because they are two entirely different issues.
Assuming the compression increase is as specified during racing, his engine doesn't comply with the rules.
That's a fact.
His engine does pass the test, though.
That's also a fact.

But passing the test doesn't make the engine legal. It only shows that the testing criteria aren't sufficient to prove the rule violation.
That's precisely why there's the overarching rule that Formula 1 cars must comply with the rules in their entirety at all times during a competition.

Toto is obviously aware of this rule. That's why he's panicking about a change in the testing criteria and throwing up smokescreens.
No one can verify his claim that everything has been coordinated with the FIA, and no one knows what inquiries or hypotheses have been submitted to the FIA ​​for clarification. Tombazi's statements certainly raise considerable doubts as to whether the FIA ​​was aware of Mercedes' intentions.

[FNTC]

Ferraris engines also "passed the tests" and fuel flow meters in 2019. But they didn't get away with it after the FIA figured it out. This might be a similar scenario. If so, a similar solution where they nerf the Merc engines somehow to compensate if they cant make them legal in time might happen.

[Bence]

The FIA just needs to expand the bore of the prechamber so that they can't close when hot. 2c part for an Xm issue, hehe.

[vorticism]

If it's just a chamber with a microscopic hole connecting it not intended to convey gas flow, it seems too cheeky. Yes it meets the wording of the rules (actually clever in that sense) but it's too against the spirit. So, I'd think, you'd need a realistic functional benefit. That's why I suggest something like a shock absorber which could aid durability in so far as metering pressure spikes. Larger hole or holes connecting it, with the volume itself actually put to use. Such a thing could be both beneficial but also difficult to tune, in which case, the complaints from the other teams. If it is actually functional in such a way as this, or some other way, then it's crocodile tears from the other teams. "Why didn't I think of that." Otherwise it's just too cheeky and too easily risks being banned.

That said, the FIA did permit for a few seasons what they later called "oil injectors" in the '17 or '18 regs, which were located in the intake manifold paths somewhere.

...

I can speculate a functional benefit of such a chamber in so far as it providing a shock absorbing feature in the event of otherwise destructive pressure spikes. Since the orifice would be too small to convey charge air without latency, it would always be lagging behind the main chamber in terms of air pressure. Thus it is lower pressure than the main chamber at TDC and can absorb pressure spikes from knock/detonation, and the passage diameter could be tuned accordiingly. The outflow would conversely display latency, with the sub-chamber retaining higher pressure for longer during the expansion stroke.

...

If the FIA were already inspecting the geometry of the TJI chambers then they will presumably be doing something similar to inspect this supposed Merc sub-chamber.