2026 Drama: Alleged engine loophole

[dialtone]

Saying “we’ve worked with them all the time and they said it’s legal” can easily mean: “2 weeks ago we asked them if 16:1 is to be respected just at ambient and they said yes”. Then FIA updated the rules and everyone else was disappointed as the rule is very black and white at the moment

To me this is the crucial issue. The fact the FIA rushed to update the technical regs after Merc asked them about it kinda makes them look complicit. There is no need to add such a detail in the regs. It's very common for this kind of measurements procedures to be detailed in appendices or technical directives, which, unlike the regulations:

1) can be enforced unilaterally and with immediate effect by the FIA
2) do not require unanimity among manufacturers to be changed

The very fact they've acted this way on wing bending, fuel flow issues, etc. and took precautions in order not to be able to the same here smells extremely fishy to me.

The part that is the funniest is that there is a non zero chance that FIA botched the rule update, or at least some mistake was made by either FIA or Merc.

The rule is black and white IMHO: 16:1 is the max, at all times.

Merc asked measured when, but the rule change following specifies the measurement condition, not the rule.

Merc simply wasn’t disturbed by this, FIA maybe thought that exceeding 16:1 was then ok, but the rule remained black and white as they only updated measurement condition. I.E. they could have updated the rule to say “Geom CR cannot exceed 16:1 at ambient temp” but instead they left the first sentence unchanged therefore not really modifying the requirement and measurement criterias change all the time during a season.

Honestly I think FIA just messed up big time.

[Y-250.A]

Those reports are from toto and that’s not how it works.

well also the latest report of changing the test from ambient into static hot also came from unreliable source from italy

Teams don’t really reveal these tricks to the FIA, they may not even show CAD drawings sometimes for these situations, they ask questions around legality of aspects of what they want to do, on top of it the timing matters of course. Saying “we’ve worked with them all the time and they said it’s legal” can easily mean: “2 weeks ago we asked them if 16:1 is to be respected just at ambient and they said yes”. Then FIA updated the rules and everyone else was disappointed as the rule is very black and white at the moment, the interpretation issue comes from past norms that nobody ever challenged and the FIA being competence challenged on its own.

as far as I know its impossible to get an accurate CR value if tested in other than ambient temperature ( the engine has to be dissembled also ) , the FIA precised ambient temperature test environment as it uses the CC-ing method which is 100% accurate.

so based on this how can they prove if Mercedes are guilty ? or even if they actually have 18:1 ratio ?
based on the rumors the trick is not solely based on expanded materials , but has another trick that works simultaneously , in this case I think its impossible to detect such CR gain at least for this season and unless they come up with a new measurement method and that will take time and efforts and also votes from all the teams .

[Forgheri_Borsari]

Its amazing in itself that a turbo engine with over 4 atmosphere's of boost can even function with a 18:1 compression ratio....but the wonders of TJI allows this. Mahle says the initial pre chamber charge event fires off at approx. 30 deg BTDC and peak pressure is occurring at 2deg ATDC.... Mahle also says the charge created in the pre chamber fires 3% of total fuel though the jet nozzles . In effect the gas jets are conditioning the air(heating) in the cylinder first at the cylinder walls moving inward and full ignition occurs when final injection 97% occurs via direct injection

Is it possible that further development in this area is allowing a larger jet volume or more strategic use of the pre chamber jets at a different moment in the crank angle to control cylinder pressure during the compression stroke ?

I say this because you can chase high compression ratios only to an extent....when your also reducing your combustion chamber size

[PlatinumZealot]

I dont think this is the case. Toto went out quite angrily 2 days ago commenting “fix your damn car” and there were reports yesterday of Merc boss saying he would take it to court. If Merc has the trick, its season over and other manufacturers will not let it slide and get embarrassed by someone loopholing their way into dominance if they feel its not by the rule.

I bet if it is that severe, there will be a TD quickly. I do not see any other levers FIA would have and it was clearly stated, that they will not allow a 2014 situation.
So maybe Merc is even playing this smart and does hide this well. Just use the trick for fuel efficiency over the race and engine wear.

At room temperature the annulus is open. Only a tiny gap in the annulus is needed for air to pass through during the compression test.

Except that the compression ratio is not measured with a compression tester, it is a measurement of the swept volume as the piston moves up and down compared to the un-swept volume when the piston is fully up. As has been stated here so many times it's getting old, it is the 'geometric' ratio. One measures the total cylinder volume when the piston is down then the total volume when the piston is up and divides one by the other.

Yes it is getting silly...
And you naughty boy describe it in a way the fans do not understand...come on...

Swept volume alone cannot measure compression ratio. You have to include the final compressed volume.

You should read, what the man writes.

A team is threatening to sue the FIA, another 3 now support it.

A fourth one is threatening to sue back if they are stopped.

The issue exists.

Yes, I also think there is much too much smoke for a nothingburger.

Atleast in this forum, the Question has now boiled down to one of the following interpretations:

A) 16:1 limit is only meant for the measurement test at ambient

No, I fear it is more just being silly for the sake of being silly. Interpretation A is what the (CURRENT) rules clearly say.

Can anyone detail the 'actual method' used by FIA to determine this ? is the traditional 'liquid/oil' displacement measurement based ? or some other fancy method ?

You call this "CAD". Right click..."measure volume"...or similar. In the homologation they work with CAD files and compare them to reality.
The "traditional method" is still used in Rally or Touring cars, where you simply can not put an engine on a 3D scan or CMM, which is no issue in F1.

Furthermore the manufacturer defines how they measure it and FIA approves this (or not). So the manufacturers have some freedom on how they define for example the TDC point of the piston as this depends also on vearing clearences, but not on anything dynamic like pressure/flexing.

If it is true with the extra volume, I do not even think there is real air going through ever. There is no minimal gap definition as far as we know for what they call the clearence volume. I think this is the loophole...there might not be any valve or similar, but really a tiny µm gap to a volume, so that under operation basically no gas will go through.

Speaking of who doesn't read...

[PlatinumZealot]

Those reports are from toto and that’s not how it works.

well also the latest report of changing the test from ambient into static hot also came from unreliable source from italy

Teams don’t really reveal these tricks to the FIA, they may not even show CAD drawings sometimes for these situations, they ask questions around legality of aspects of what they want to do, on top of it the timing matters of course. Saying “we’ve worked with them all the time and they said it’s legal” can easily mean: “2 weeks ago we asked them if 16:1 is to be respected just at ambient and they said yes”. Then FIA updated the rules and everyone else was disappointed as the rule is very black and white at the moment, the interpretation issue comes from past norms that nobody ever challenged and the FIA being competence challenged on its own.

as far as I know its impossible to get an accurate CR value if tested in other than ambient temperature ( the engine has to be dissembled also ) , the FIA precised ambient temperature test environment as it uses the CC-ing method which is 100% accurate.

so based on this how can they prove if Mercedes are guilty ? or even if they actually have 18:1 ratio ?
based on the rumors the trick is not solely based on expanded materials , but has another trick that works simultaneously , in this case I think its impossible to detect such CR gain at least for this season and unless they come up with a new measurement method and that will take time and efforts and also votes from all the teams .

As I suggested, the FIA may not need fo measure the compression ratio with the engine on a test bench (imagine doing this for all five engines makes!) ; instead the parts can be inspected to determine if there is "intention" to raise the CR.
For example take out the connecting rod heat it uniformly, measure the growth. Like-wise with the block. for the head inspect for any unusual crevices, features etc. How do they compare to similar parts from previous years etc and accross competitors.

[bluechris]

but a few days ago before barcelona shakedown or during I can't remember , reports said that the FIA approved Mercedes Engine and its complied with the rules ; so what changed since then ? also who said they have such trick ? I mean no official release nor statement from FIA , all this choas based only on speculations and protests , what if mercedes also couldn't make the trick work as it didn't even pass the theoretical phase ; few days ago also TOTO said the engine is within the rules and they were working with the FIA with each step and got the green light for the next step , also the statements refered to Mercedes CEO are not true , a proved to be false

Those reports are from toto and that’s not how it works.

Teams don’t really reveal these tricks to the FIA, they may not even show CAD drawings sometimes for these situations, they ask questions around legality of aspects of what they want to do, on top of it the timing matters of course. Saying “we’ve worked with them all the time and they said it’s legal” can easily mean: “2 weeks ago we asked them if 16:1 is to be respected just at ambient and they said yes”. Then FIA updated the rules and everyone else was disappointed as the rule is very black and white at the moment, the interpretation issue comes from past norms that nobody ever challenged and the FIA being competence challenged on its own.

If you ever worked in a regulated competitive environment you probably did something like this with your lawyers or the regulator lawyers. Your questions imply what you are trying to do but don’t necessarily reveal it in full.

FIA has the power to completely disassemble a whole engine after a race, no? They are the governing body or not?

[peewon]

Saying “we’ve worked with them all the time and they said it’s legal” can easily mean: “2 weeks ago we asked them if 16:1 is to be respected just at ambient and they said yes”. Then FIA updated the rules and everyone else was disappointed as the rule is very black and white at the moment

To me this is the crucial issue. The fact the FIA rushed to update the technical regs after Merc asked them about it kinda makes them look complicit. There is no need to add such a detail in the regs. It's very common for this kind of measurements procedures to be detailed in appendices or technical directives, which, unlike the regulations:

1) can be enforced unilaterally and with immediate effect by the FIA
2) do not require unanimity among manufacturers to be changed

The very fact they've acted this way on wing bending, fuel flow issues, etc. and took precautions in order not to be able to the same here smells extremely fishy to me.

The part that is the funniest is that there is a non zero chance that FIA botched the rule update, or at least some mistake was made by either FIA or Merc.

The rule is black and white IMHO: 16:1 is the max, at all times.

Merc asked measured when, but the rule change following specifies the measurement condition, not the rule.

Merc simply wasn’t disturbed by this, FIA maybe thought that exceeding 16:1 was then ok, but the rule remained black and white as they only updated measurement condition. I.E. they could have updated the rule to say “Geom CR cannot exceed 16:1 at ambient temp” but instead they left the first sentence unchanged therefore not really modifying the requirement and measurement criterias change all the time during a season.

Honestly I think FIA just messed up big time.

Many people are thinking that the FIA update about "ambient temperature" came because Mercedes sought clearance from FIA for their design. To me this scenario is impossible. There is 0 chance Mercedes was developing a PU for all these years in a grey area risking being banned. They had to have know well in advance that their design would be accepted by the FIA.

Everyone in the paddock has believed for a long time they will have the best PU. Alpine ditched a promising works PU program to become a customer. This is not all co-incidental.

So the question becomes why the FIA waited so long to make this update? And for me there is no good answer to this question apart from collusion with Merc. They have basically removed the grey area and codified the loophole in favor of Mercedes. The only measurement compliance required now is at ambient temperature. If they made the change earlier, other teams would have suspected something being done in that area. This was done at a time when it was almost impossible to make drastic changes in design. Its a smoking gun to all of this being shady.

[Y-250.A]

As I suggested, the FIA may not need fo measure the compression ratio with the engine on a test bench (imagine doing this for all five engines makes!) ; instead the parts can be inspected to determine if there is "intention" to raise the CR.
For example take out the connecting rod heat it uniformly, measure the growth. Like-wise with the block. for the head inspect for any unusual crevices, features etc. How do they compare to similar parts from previous years etc and accross competitors.

the problem here is that the CR 18:1 is not feasible or relying only on thermal expansion of metals ( else RBPT achieved the CR also ) , its more complicated and has a hidden feature that works simultaneously under precised environment ( heat , expansion , chemicals etc ...) , and also any test occurred on any temperature rather than ambient will mislead the result ( for example if the engine is running @ 120 C° the CR will 16.3 till 16.5 ) , the FIA stated that the manufacture performs the TEST under ambient temperature while the engine is dissembled : "Every manufacturer must have their specific measurement procedure, based on C042 guidelines, approved by the FIA Technical Department and included in their official homologation dossier " and also I don't think MB will be that naive or stupid to install a hidden chambre or a new parts behind the FIA's back , that would be a total death certificate for their season .

I think the most doable solution will be applying a new test starting from 2027 season and that's the closest settlement I guess for all .

[gearboxtrouble]

They should be able to use in cylinder pressure sensors to measure compression during operation - i'd be surprised if the teams haven't already been using them to optimize combustion during development.

[AR3-GP]

As I suggested, the FIA may not need fo measure the compression ratio with the engine on a test bench (imagine doing this for all five engines makes!) ; instead the parts can be inspected to determine if there is "intention" to raise the CR.
For example take out the connecting rod heat it uniformly, measure the growth. Like-wise with the block. for the head inspect for any unusual crevices, features etc. How do they compare to similar parts from previous years etc and accross competitors.

the problem here is that the CR 18:1 is not feasible or relying only on thermal expansion of metals ( else RBPT achieved the CR also ) , its more complicated and has a hidden feature that works simultaneously under precised environment ( heat , expansion , chemicals etc ...)

Anecdotal:

One way to reduce the volume at TDC is to increase the length of the connecting rod, which happens naturally on every engine, and which explains why I think everyone has been doing this for years. On Formula 1 engines that I have worked on, at maximum engine speed the rod stretches by around 0.2mm due to the inertial load from the piston, so there is an inherent increase in compression ratio, whether you want it or not.

There is talk by some that Mercedes and Red Bull are reaching 18.0:1, which would equate to a rod stretch of around 0.5mm. I wouldn’t be surprised to find out that they have cleverly designed the rod to expand in length due to a combination of the piston inertial load and thermal expansion. This would almost certainly be legal, as there is no regulation about the longitudinal stiffness or thermal expansion coefficient of the connecting rod.

https://modatek.co.uk/f1-compression-ra ... 3b97fa6688


A stretching connecting rod due to inertial forces (0.2mm) and thermal expansion (0.15-0.2mm) combined with a low thermal expansion cylinder head (-0.15mm compared to high expansion) would achieve the 0.5mm required to raise the compression ratio from 16 to 18. Whether someone is doing this is another matter entirely.

The conflict (if you believe the internet) is that some teams have designed engine to operate at 16:1 when warm (factoring in thermal expansion, inertial stretch, and so on) while others have designed it for the test at ambient, and allow it to increase when warm. All alleged, of course. Whispers and a working theory are not proof.

[Tommy Cookers]

the conflict is that some (including some FIA etc) think there is such a thing as CR of a running engine
there is no such thing .....
the CR of a running engine was and so is (by definition) the CR the engine has when not running

because ....
(people thinking the Otto engine was the first volume-produced ICE)
they don't know that the Otto had patented a unique and completely new feature - it did compressing
(cos they don't know the first volume-produced ICE (Lenoir gas engine) didn't do compressing)

btw ....
if we include eg the volumetric distortions in running engines all WDCs are void (due to engines oversize when running)
all except 1958 & 1959 when the winning engines had a margin capacity-wise, being stretched F2 engines

[AR3-GP]

the conflict is that some (including some FIA etc) think there is such a thing as CR of a running engine
there is no such thing .....

The compression ratio is geometric. So it is well defined at any temperature. Whether it can be physically measured when running is another topic.

[PlatinumZealot]

As I suggested, the FIA may not need fo measure the compression ratio with the engine on a test bench (imagine doing this for all five engines makes!) ; instead the parts can be inspected to determine if there is "intention" to raise the CR.
For example take out the connecting rod heat it uniformly, measure the growth. Like-wise with the block. for the head inspect for any unusual crevices, features etc. How do they compare to similar parts from previous years etc and accross competitors.

the problem here is that the CR 18:1 is not feasible or relying only on thermal expansion of metals ( else RBPT achieved the CR also ) , its more complicated and has a hidden feature that works simultaneously under precised environment ( heat , expansion , chemicals etc ...) , and also any test occurred on any temperature rather than ambient will mislead the result ( for example if the engine is running @ 120 C° the CR will 16.3 till 16.5 ) , the FIA stated that the manufacture performs the TEST under ambient temperature while the engine is dissembled : "Every manufacturer must have their specific measurement procedure, based on C042 guidelines, approved by the FIA Technical Department and included in their official homologation dossier " and also I don't think MB will be that naive or stupid to install a hidden chambre or a new parts behind the FIA's back , that would be a total death certificate for their season .

I think the most doable solution will be applying a new test starting from 2027 season and that's the closest settlement I guess for all .

I did the maths earlier in the thread and It is not feasible on thermal expansion alone. However in combination with a pocket or chamber in the cylinder head or piston it is very possible. Yes I have changed my stance on the topic. It is possible but I don't think the manufacturers are doing it becauase they would have done this already in the previous rule set to get a winning edge.

The hidden pocket or chamber would have a conical plug that needs only to expand by a few thousanths to plug the annular passage to the chamber.
Technically the problem would be this would be clearly seen as a way to cheat because:
1) the chamber would be inlcuded in the geometric compression ratio demonstrated to the FIA

2) contrary to item 1 above, it relies on a gas property compression ratio measurement to show that it is 16:1 at room temp, if this chamber is not to be declared to the FIA

OR
3) the chamber is declared to the FIA and the FIA sees that there is a channel with a suspiscious conical plug in the centre of it and does nothing further to investigate.

So these three problems is why I think it is possible but non of the teams are doing this trick. It's like turning a blind eye towards intention to cheat the spirit of the rules.

[PlatinumZealot]

They should be able to use in cylinder pressure sensors to measure compression during operation - i'd be surprised if the teams haven't already been using them to optimize combustion during development.

With valve overlap difference you can't rely rely on this with a fully assembled engine. You would have to remove the cam shafts or lock them so all valves are fully closed then yeah you should be able to measure adiabatic compression ratio.

[AR3-GP]

I asked Gemini (AI) how the compression ratio could be measured while hot.

The first suggestion is unlikely in 2026 because they no longer have the pressure sensor in the cylinder. 2nd suggestion is not going to happen since it requires new design. Only the final suggestion is plausible. Heat the engine to operating temperature on a bench using coolant and oil. Then do the measurement.