2026 Drama: Alleged engine loophole

[basti313]

FIA ASKING THE TEAMS TO SUBMIT A METHOD TO MEASURE COMPRESSION RATIO.

Teams are also asked to provide an adaptor for holding the front wing planes when wing flex is measured.
This might be different… or not.
We still don’t know what is in that appendix, it might be super-restrictive in what is to tested and how, or it might be farcically loose. But we don’t know. And we don’t know what we don’t know.
Until (if) we know, going for absolutes seems a bit … opinion.

With this amount of smoke, and the sources of said smoke, it looks like there is something going on. But what? we are shooting in the dark.

Well the process is actually clear for the CR: The manufacturer makes a calculation of the CR from the CAD data, involves tolerances and the FIA checks if this makes sense.
I do not think this is "farcically loose", but actually the opposite. With having the last word on accepting the calculation, the FIA can always say "stop" if tolerances are fishy and can compare if everyone is doing this calculation on fair and similar grounds. If they start defining methods, it just gets more messy.

With this amount of smoke, and the sources of said smoke, it looks like there is something going on. But what? we are shooting in the dark.

I am just starting to compare engine parameters. But the main difference is the CR, that I could find in dimensions/design parameters.
Maybe the simple smart move was to go with the 2025 engine, adjust the head and some parts to the new requirements and just add a dead volume to come to the necessary CR. Would save a lot of hours on design that can be used better on other parts of the engine.

...You have said without any proof that other teams are operating above 16 CR when running. ...

I still do not get, why you are debating "when running" on the loophole. If anything is known, then that there is no rule on "when running". It is black on white in the rules "ambient".

I think all this discussion on a potential new rule and new test might be better discussed in a separate thread:
- One thread for the actual trick under the current ruleset
- One thread for a new TD or rule change to prevent the trick

I think this mixed discussion in the unclear status quo and a potential new rule on also unclear grounds makes this thread very messy.

The most farcical thing about this whole saga, is :
FIA ASKING THE TEAMS TO SUBMIT A METHOD TO MEASURE COMPRESSION RATIO.
why ? the people who 'frame a formula' don't have the know-how to define a way to test/measure the compression ratio of an engine ? that too, geometric compression ratio ?
I don't know whether this is FIA being lazy ? facetious ? stupid ? corrupt ? or all together ?
The more I read this thread, the more disillusioned I become.

No, I think this is a simple curve ball:
There is simply no "test" one can quickly do on a hot engine and that would reveal a dead volume during combustion.
So teams can not come up with this test and this is one part of the game to put the whole discussion to the side for this season.

[Stu]

I’ve just had a thought….
Adding a ‘secret’ chamber in the head with an entry point large enough to allow the designated measuring fluid (parafin normally) to enter at ambient temperature but small enough to not allow any combustion gases to enter would entail using a sharp edge to the hole, this would create the potential for a hot-spot and cause premature detonation. This would be a bad thing!
If I were to look at creating the additional volume in a way that there is a secondary use for it I would be 3D printing my pistons with a hollow support structure between the gudgeon pin support and the crown (much like they did with the wheel spokes a few years ago), reduced mass, increased surface area and additional cooling benefit from the oil cooling sprays under the piston.

[Sieper]

But if you (cut) open a used engine you could see those extra spaces. wherever they are. That would be, in my opinion, a clear DSQ. This would be hard to do as you might have to damage the engine, and then what? Allow to use a new one (under the budget?) but still. Any engineering with extra spaces to me should be non permissible. That is the same as extra fuel flow.

What I first thought (when I heard Mercedes was achieving a higher compression ratio) was that the connection rod would expand when it gets hot, pushing the piston up higher and changing the compression ratio. That would be something where it is a real grey area imho. I guess this happens in all engines anyway?! Or there is no room for the piston to go up any higher?

[upsidedowntoast]

Keep in mind we still have no idea if this secret chamber even exists. The first time I ever heard of this secret chamber was the German autosport magazine which tossed out the theory as a devil's advocate, and the very next sentence was "we ran this by an f1 engineer and they said 'no that would get banned immediately'".

[WardenOfTheNorth]

I cannot see how they'd get the secret chamber through. They have to submit CAD designs to The FIA don't they?

A secret chamber, if discovered, would destroy Merc reputation.

I think the most likely option is thermal expansion at operating temperature. The Driver61 video was able to explain how this could be done, and that was just based in his knowledge, let alone what the clever brains at Mercedes can come up with.

[basti313]

I’ve just had a thought….
Adding a ‘secret’ chamber in the head with an entry point large enough to allow the designated measuring fluid (parafin normally) to enter at ambient temperature but small enough to not allow any combustion gases to enter would entail using a sharp edge to the hole, this would create the potential for a hot-spot and cause premature detonation. This would be a bad thing!

I do not think you can get any fluid through a hole that prevents combustion gases. This would be sub 0.3mm, you do not get anything like oil or parfine through it.
But as it is calculated, that is no issue.
I also do not see a big issue...as mentioned before a smart placing would be for example in the injector. There you can use hard enough material and you get enough cooling. Just needs to be away from the exhaust valve.

I cannot see how they'd get the secret chamber through. They have to submit CAD designs to The FIA don't they?

Why secret chamber? There is no rule preventing them from introducing a second chamber. It does not have to be in any way secret.

[dialtone]

I’ve just had a thought….
Adding a ‘secret’ chamber in the head with an entry point large enough to allow the designated measuring fluid (parafin normally) to enter at ambient temperature but small enough to not allow any combustion gases to enter would entail using a sharp edge to the hole, this would create the potential for a hot-spot and cause premature detonation. This would be a bad thing!

I do not think you can get any fluid through a hole that prevents combustion gases. This would be sub 0.3mm, you do not get anything like oil or parfine through it.
But as it is calculated, that is no issue.
I also do not see a big issue...as mentioned before a smart placing would be for example in the injector. There you can use hard enough material and you get enough cooling. Just needs to be away from the exhaust valve.

The point isn't so much that a liquid enters vs a gas, it's that like all pipes they have a certain maximum flow that can go through them for a given fluid in a given unit of time. Given ignition timing, a small enough pipe while in a CAD design, or even under relaxed timing situations, may fill up with fluid, when reaching the ignition timing there is simply not enough time to flow the fluid in and out of there.

I also wonder, if such a chamber exists anyway, if there's no exhaust out of that chamber the internal pressure in it eventually grows enough that it virtually prevents entry of any gas, so even without thermal expansion they may just end up at a place where that separate chamber is practically sealed. Would this even be efficient or possible? Because if the gas buildup in it makes the system inefficient then I wonder if this is even happening.

I cannot see how they'd get the secret chamber through. They have to submit CAD designs to The FIA don't they?

Why secret chamber? There is no rule preventing them from introducing a second chamber. It does not have to be in any way secret.

C5.1.3 All engines must have six cylinders arranged in a 90° “V” configuration and the normal section of
each cylinder must be circular.

If you have a "secret" chamber, unless you put it right at the top of the cylinder, cannot be a circular normal section.

[basti313]

I also wonder, if such a chamber exists anyway, if there's no exhaust out of that chamber the internal pressure in it eventually grows enough that it virtually prevents entry of any gas, so even without thermal expansion they may just end up at a place where that separate chamber is practically sealed. Would this even be efficient or possible? Because if the gas buildup in it makes the system inefficient then I wonder if this is even happening.

Yes, I calculated the size in the other more technical thread on this topic. 0.3mm and 3cm length and you do not get the wavefront of the combustion through it.
I do not think the pressure matters at all. Will go to some middle pressure...and it is actually a quite small volume.

C5.1.3 All engines must have six cylinders arranged in a 90° “V” configuration and the normal section of
each cylinder must be circular.

If you have a "secret" chamber, unless you put it right at the top of the cylinder, cannot be a circular normal section.

Good point. But I think this does not have any influence on the cylinder head. There is no circular normal section on the head. Would this rule make sense on the head?

[Hoffman900]

This chamber idea doesn’t make any engineering sense.

I can guarantee 230bar+ of cylinder pressure is going to find its way through a 0.3mm gap.

[upsidedowntoast]

I cannot see how they'd get the secret chamber through. They have to submit CAD designs to The FIA don't they?

A secret chamber, if discovered, would destroy Merc reputation.

I think the most likely option is thermal expansion at operating temperature. The Driver61 video was able to explain how this could be done, and that was just based in his knowledge, let alone what the clever brains at Mercedes can come up with.

This chamber idea doesn’t make any engineering sense.

That's what I've been saying. I see it thrown around everywhere -- this forum, reddit, x.com, youtube, written news outlets...and while it's ok discussing it as a theoretical, some people are acting like this is the mystery solved.

Thing is, I remember exactly where I first saw the hidden chamber theory proposed and then immediately dismissed:

https://www.auto-motor-und-sport.de/for ... orentrick/

"In recent weeks, rumors have been circulating that the engineers may have connected a small pocket with a volume of one cubic centimeter to the combustion chamber via a very thin channel. The access point to this channel is said to be located near the pre-chamber spark plug at the very top of the cylinder. During the static test, this volume fills up as the piston moves upwards. However, during normal driving, at higher temperatures and engine speeds, a critical pressure value must be exceeded so that the volume does not expand into the narrow channel during compression. This would increase the compression ratio. That was the theory, at least...An inquiry with the FIA ​​reportedly revealed that the trick, as described, is not permitted – or so one engine engineer told us."

I personally think that a chamber like this would a) show up too obviously in the CAD files that Merc would have had to share with the FIA, and b) would be significantly easier to copy by RBPT than alternative proposals. My gut says that the trick is a combination of a material with positive thermal expansion, a material with negative thermal expansion, and a special internal 3D printing pattern that aligns them both in a unique way.

[Hoffman900]

The whole chamber idea is right up there with Scarb’s idea / drawing that that a pendulem weight can change brake balance with gforces, that’s not how physics work.

This is a good time to remind people that F1 media people don’t have any experience in this stuff (most have journalism degrees and no motorsport experience outside “reporting”), nor do forum members, reddit users, etc. and clicks sell, so no such thing as a bad take anymore.

[autodoctor911]

I think the obvious work around is not new materials but an extra chamber off the prechamber that will become fully closed off at full race temperature by bimetallic expansion or some other substance pushing the "valve" to seal thoa extra chamber off under race conditions. No test change to eliminate that seems infeasible. Even straight off the track that would be able to bypass a quick measurement of chamber volume unless they use a very hot fluid to measure the volume
Edit: hadn't read above or seen scares or anyone that actually put out any kind of plausible theory yet. Even if the FIA saw it. They must have approved it. That's why most teams wouldn't think to even try it. It's just hard to reverse the course at this point if they already approved the designs and no new test would be applicable to eliminate it

[autodoctor911]

Even then they could use the dynamics of the engine running to help keep the chamber volume sealed and split off and temperature alont would not seal it

[autodoctor911]

Also. One could argue that the chamber had a legitimate purpose for combustion purposes. Heck maybe you could do something with it to help combustion before it closes off at full load. At lighter loads it could store some air out of the fuel stream to help start combustion when not as much air is forced in yet

[upsidedowntoast]

This is very unlikely given the amount of chatter and smoke present, but I would *love* the truth to be that there was no special secret compression ratio trick, but something else -- and in fact Mercedes came to the same conclusion as Red Bull awhile back which is that "yeah we tried and this doesn't work". And the fear around the test change isn't that it will render their engines illegal, but that it will reveal their engines weren't special at all, drawing attention to something else that they're doing.