2026 Drama: Alleged engine loophole

[SpecialOps]

It was clear as day right from the beginning that there was something going on. It surprises me that some still didn't believe or want to believe it until now.

Wolff is the biggest politician in F1. No wonder he's hypocritical - it's his job after all.

What frustrates me is that there are people calling this compression ratio trickery "pushing boundaries" or "being clever". I'm 100% sure every single PU manufacturer out there would have been able to replicate this, but they didn't. They didn't because they wanted their PU to be compliant with the rules which state that the compression ratio must be 16:1 at all times. It being measured at ambient temperature should not change this fact.

And for those being extremely pedantic, I know that compression ratio always changes at operating temperatures, but it's another thing to build your engine specifically around this and with the aim to increase the compression ratio as much as possible.

Mercedes tells the FIA into their face that they have a trick where the compression ratio is 16:1 when being measured, but as high as 18:1 when operating even though the rules state that this is prohibited. And the FIA say that they are OK with that. Imagine that... what a scandal.
If the rule of the measurement at ambient temperature was added after the engines were built, it's an even bigger scandal.

Like I predicted right from the first day I've heard this: The FIA will eventually ban this for "cost reasons", but only in 2027 at the earliest.

And the fact that the ambient temperature clarification was only introduced in October last year? Without that added clarification from FIA what would have happened and why did they leave it until that much later to add it to the rules? That additional clarification is the only reason why the Mercedes and RBPT is now legal.

[CHT]

A lot has been said and discussed about 16:1 > 18:1 compression ratio using thermal expansion as a trick and its challenges. Just curious why must it be 18:1? Will 17:1 or 17.5:1 generate meaningful gains for the manufacturer?

[Stu]

As I see it, the problem is (as usual) with the wording of the regs (rather than the intention). The old ICE regs put a cap of 18:1 on CR at any time, the new ones appear to move that down to 16:1, but specify roughly the temperature at which it will be measured.

Just to be clear, this measurement temperature change was made in October 2025.

The complexity isn’t that expansion is hard to model, it isn’t, but that the rule was interpreted differently by different teams because it was, and still is, badly written.

If this is left standing, the literal only fair solution is that teams that didn’t design for this get to continue development of the engine to bridge that gap.

I don’t call this cheat, as the 2019 Ferrari wasn’t either, but it’s bad faith and incompetence from FIA whose goal should be a level playing field. When you change interpretation of the rules that late you have to give time for others to adjust and not freeze their engines.

^^This^^

A sudden descent of FIA stewards at the end of the official test and subsequent random batch testing at the first 3 races would be a great idea. If they followed up with a clear TD as to which teams were permitted to ‘equalise’ to the testing criteria it would be perfect…

…but I doubt that the FIA would do that!

In all seriousness, if Audi, for example, have designed their ICE around the concept of not exceeding 16:1 “at any time” and there are legal materials being used that allow that to increase to just under 16:1 at operating temperature and speed they will be at a massive disadvantage to any team running a PU that has the same tech but built to 16:1 ‘cold’.
It isn’t just the ICE, the fuel partners will have been maximising the fuel composition around the operating window, cooling systems will be optimised around the operating temperatures, control software will be optimised, etc, etc.
The late regulation change will have a lasting effect throughout at least this season (and probably through to the proposed end of these PU regulations).
When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

[SpecialOps]

As I see it, the problem is (as usual) with the wording of the regs (rather than the intention). The old ICE regs put a cap of 18:1 on CR at any time, the new ones appear to move that down to 16:1, but specify roughly the temperature at which it will be measured.

Just to be clear, this measurement temperature change was made in October 2025.

The complexity isn’t that expansion is hard to model, it isn’t, but that the rule was interpreted differently by different teams because it was, and still is, badly written.

If this is left standing, the literal only fair solution is that teams that didn’t design for this get to continue development of the engine to bridge that gap.

I don’t call this cheat, as the 2019 Ferrari wasn’t either, but it’s bad faith and incompetence from FIA whose goal should be a level playing field. When you change interpretation of the rules that late you have to give time for others to adjust and not freeze their engines.

^^This^^

A sudden descent of FIA stewards at the end of the official test and subsequent random batch testing at the first 3 races would be a great idea. If they followed up with a clear TD as to which teams were permitted to ‘equalise’ to the testing criteria it would be perfect…

…but I doubt that the FIA would do that!

In all seriousness, if Audi, for example, have designed their ICE around the concept of not exceeding 16:1 “at any time” and there are legal materials being used that allow that to increase to just under 16:1 at operating temperature and speed they will be at a massive disadvantage to any team running a PU that has the same tech but built to 16:1 ‘cold’.
It isn’t just the ICE, the fuel partners will have been maximising the fuel composition around the operating window, cooling systems will be optimised around the operating temperatures, control software will be optimised, etc, etc.
The late regulation change will have a lasting effect throughout at least this season (and probably through to the proposed end of these PU regulations).
When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

100% to me this whole drama screams incompetence from the FIA. How long did they know about what Mercedes was up to and why did they wait until Oct 25 to clarify that way the ratio is measured. By reducing the compression ratio in the hope of allowing more engine manufacturers into the sport they’ve created a whole other problem. Why couldn’t they just leave the compression ratio as per the previous reg cycle. This isn’t just a HP advantage, the cars will be more fuel efficient and carry less fuel to start the races. I can’t believe how incompetent the FIA has been.

[LM10]

When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

There was nothing to clarify to begin with. Go to a 5 year old kid and ask what “must not exceed 16:1 at all times” means and it will tell you.

The sole fact that the measurement temperature change was made as late as in October 2025 is outrageous in itself.

Three options:
1. Mercedes BEFORE starting to build their PU and optimizing everything around this (which must have been ages ago) asked for clarification
2. Mercedes built their PU without the intend to ask for clarification, but the FIA somehow found out about it
3. Mercedes AFTER having built their PU asked for clarification

I don’t see how any of these options is fair towards competition and not ranging from borderline scandalous (option 1) to downright scandalous (options 2 and 3).

This is not incompetence. The FIA exactly knew what they were doing.

[Espresso]

Hahaha Toto is great.
Summary (as the interview is in German):

Stop whining like a litlle child when we got something fully within the regulations and you do not. rules are black and white clear on paper. And our communications with the FIA are very clear/transparant. But it´s just sad that as soon as a team discovers something....the other teams sneaky forces/pushes/threatens the FIA to change the rule...

Value it as it is.

[Badger]

When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

There was nothing to clarify to begin with. Go to a 5 year old kid and ask what “must not exceed 16:1 at all times” means and it will tell you.

The sole fact that the measurement temperature change was made as late as in October 2025 is outrageous in itself.

Three options:
1. Mercedes BEFORE starting to build their PU and optimizing everything around this (which must have been ages ago) asked for clarification
2. Mercedes built their PU without the intend to ask for clarification, but the FIA somehow found out about it
3. Mercedes AFTER having built their PU asked for clarification

I don’t see how any of these options is fair towards competition and not ranging from borderline scandalous (option 1) to downright scandalous (options 2 and 3).

This is not incompetence. The FIA exactly knew what they were doing.

Dial back the outrage a bit and actually look at the facts. The FIA has come out and explicitly said that the measurement procedure has remained the same. They added verbiage to the regulations for clarification, but they did not change the procedure. It was always ambient.

[Watto]

When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

There was nothing to clarify to begin with. Go to a 5 year old kid and ask what “must not exceed 16:1 at all times” means and it will tell you.

The sole fact that the measurement temperature change was made as late as in October 2025 is outrageous in itself.

Three options:
1. Mercedes BEFORE starting to build their PU and optimizing everything around this (which must have been ages ago) asked for clarification
2. Mercedes built their PU without the intend to ask for clarification, but the FIA somehow found out about it
3. Mercedes AFTER having built their PU asked for clarification

I don’t see how any of these options is fair towards competition and not ranging from borderline scandalous (option 1) to downright scandalous (options 2 and 3).

This is not incompetence. The FIA exactly knew what they were doing.

I would lean towards options 1. We saw with RBR last year about how McLaren were cooling their tyres they peppered the FiA with can we do this iirc McLaren said they checked with the FIA when designing it too but that one is a bit more of a sketchy memory. But I recall teams/someone saying these kinds of queries are pretty normal between the FIA and teams.

Mercedes did it early maybe a little later on RBR asked more questions from their ex Mercedes PU engineers and the FIA clarified with their change?

[LM10]

When Mercedes & RBPT went to the FIA with the request to ‘clarify’ their interpretation of the regs why on earth didn’t the FIA say “it is clearly written as it has been for 16 years”?

Poor management…..

There was nothing to clarify to begin with. Go to a 5 year old kid and ask what “must not exceed 16:1 at all times” means and it will tell you.

The sole fact that the measurement temperature change was made as late as in October 2025 is outrageous in itself.

Three options:
1. Mercedes BEFORE starting to build their PU and optimizing everything around this (which must have been ages ago) asked for clarification
2. Mercedes built their PU without the intend to ask for clarification, but the FIA somehow found out about it
3. Mercedes AFTER having built their PU asked for clarification

I don’t see how any of these options is fair towards competition and not ranging from borderline scandalous (option 1) to downright scandalous (options 2 and 3).

This is not incompetence. The FIA exactly knew what they were doing.

Dial back the outrage a bit and actually look at the facts. The FIA has come out and explicitly said that the measurement procedure has remained the same. They added verbiage to the regulations for clarification, but they did not change the procedure. It was always ambient.

It does not change the fact that the CR must not exceed 16:1 at all times. It’s simple as that really. If the measurement is what counts, Ferrari’s 2019 engine was as compliant as Mercedes’ current one.

Double standards… no other explanation.

[Badger]

Wolff:

"The regulations are completely clear and were agreed with the FIA. We don't like the fact that they just don't admit it to themselves and that the nags keep coming around the corner."

"And then there are secret meetings and letters are sent.

Do your job! This is something that I have been strongly propagating here in recent years. We no longer focus on what others do. We no longer complain all the time, but we try to make the best possible out of our package."

"They come up with a new initiative every week and try to argue something that is not argumentable. Maybe they're looking for excuses to keep their bosses happy and therefore argue that something is not legal, which is one hundred percent legal.

"The rules have been written in black and white for a long time. And the way in which the compaction ratio is measured is a well-known process across the industries. There is no other way. Everything else is inventions.”

"The process, the communication between the FIA and us is impeccable. This is a positive development, because it is not only about this one engine issue. There is basically mutual, open and transparent communication."

https://www.motorsport-magazin.com/for ... onkurrenz/

[Badger]

There was nothing to clarify to begin with. Go to a 5 year old kid and ask what “must not exceed 16:1 at all times” means and it will tell you.

The sole fact that the measurement temperature change was made as late as in October 2025 is outrageous in itself.

Three options:
1. Mercedes BEFORE starting to build their PU and optimizing everything around this (which must have been ages ago) asked for clarification
2. Mercedes built their PU without the intend to ask for clarification, but the FIA somehow found out about it
3. Mercedes AFTER having built their PU asked for clarification

I don’t see how any of these options is fair towards competition and not ranging from borderline scandalous (option 1) to downright scandalous (options 2 and 3).

This is not incompetence. The FIA exactly knew what they were doing.

Dial back the outrage a bit and actually look at the facts. The FIA has come out and explicitly said that the measurement procedure has remained the same. They added verbiage to the regulations for clarification, but they did not change the procedure. It was always ambient.

It does not change the fact that the CR must not exceed 16:1 at all times. It’s simple as that really. If the measurement is what counts, Ferrari’s 2019 engine was as compliant as Mercedes’ current one.

Double standards… no other explanation.

Incorrect, the FIA have a measurement process to enforce this rule and it specifies ambient temperature. Same way we don’t disqualify cars with flexi-wings if they pass the static load test. Same way we don’t check cylinder volumes at operating temperatures, because they would be above 1600cc.

Ferrari tampered with the fuel flow sensor, there was a rule expressly prohibiting this. Totally illegal.

[Schumix]

Incorrect, the FIA have a measurement process to enforce this rule and it specifies ambient temperature. Same way we don’t disqualify cars with flexi-wings if they pass the static load test. Same way we don’t check cylinder volumes at operating temperatures, because they would be above 1600cc.

Ferrari tampered with the fuel flow sensor, there was a rule expressly prohibiting this. Totally illegal.
[/quote]

If I remember correctly, Ferrari hadn't tampered with the fuel flow sensor mandated by the FIA. Ferrari had found a way to increase the fuel flow passing through this sensor without altering the sensor itself. The FIA ​​sensor measured the fuel flow at precise time intervals, and the measurement taken on the Ferrari engine was compliant. Otherwise, the FIA ​​would have detected the anomaly. However, between two fuel flow measurements, the Ferrari engine's flow exceeded the specified value. The result: the Ferrari engine's fuel flow complied with the FIA ​​tests, but not at every moment of its operation. This is exactly the situation with the 2026 Mercedes engine. The FIA ​​began secret discussions with Ferrari in 2019, and Ferrari offered to install a second sensor to prevent any other engine manufacturer from exploiting this technical loophole. It's a bit frustrating for us F1 fans that this controversy is spoiling what promises to be an exciting championship.

[LM10]

Dial back the outrage a bit and actually look at the facts. The FIA has come out and explicitly said that the measurement procedure has remained the same. They added verbiage to the regulations for clarification, but they did not change the procedure. It was always ambient.

It does not change the fact that the CR must not exceed 16:1 at all times. It’s simple as that really. If the measurement is what counts, Ferrari’s 2019 engine was as compliant as Mercedes’ current one.

Double standards… no other explanation.

Incorrect, the FIA have a measurement process to enforce this rule and it specifies ambient temperature. Same way we don’t disqualify cars with flexi-wings if they pass the static load test. Same way we don’t check cylinder volumes at operating temperatures, because they would be above 1600cc.

Ferrari tampered with the fuel flow sensor, there was a rule expressly prohibiting this. Totally illegal.

CR must not exceed 16:1 at all times. Period. Not hard to interpret. Read it again.

Rear wings have dots to measure flexing while in motion. Added in 2021 to prevent flexing after passing static load tests.

What will the FIA do in case of CR? Because you know, there is a rule, read my first sentence again.

[AnotherAlex]

Ferrari tampered with the fuel flow sensor, there was a rule expressly prohibiting this. Totally illegal.

Ferrari did NOT tamper with the fuel flow sensor. Any idiot could do that and even those at the FIA would likely spot it. Ferrari had a pulsed fuel flow that was synchronised with the fuel flow sensor's sampling, which I think was 2000 times per second, so it was a rather clever trick and getting it to work an impressive achievement. That said, its purpose was to get around the fuel flow limits so no surprise when the flow rate monitoring was changed to prevent it.

BTW, there has been a long standing rule expressly forbidding the burning of oil as fuel, but that didn't stop it from being a decisive factor when the last major engine rule change was introduced.

[Edit: Sorry Schumix, I missed your post above, but I agree completely.]

[FittingMechanics]

What is interesting to me is whether all the engines pass these 16:1 at working temperature test? I'd assume that they don't, they all probably designed to be 16:1 at ambient temperature as it is measured, but they didn't realize they can push this a lot further than 16:1. So my assumption is everyone is at least 16.1-16.2 and then Mercedes pushed this to the extreme and is running significantly higher.

Maybe Audi is 16:1 at all times and the rest are not? I'd be really surprised if this was changed at the last minute.