2026 Drama: Alleged engine loophole

[gearboxtrouble]

AMUS has an article suggesting Mercedes may have a small 1-cubic-centimeter pocket in the spark plug area connected through a small channel. During static tests, this channel remains open to pass the test, but at higher racing temperatures, a pressure valve closes, increasing the ratio.

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

This would violate the cubic capacity limits no?

Not if the engine is 1599cc at operating temp.

[AR3-GP]

AMUS has an article suggesting Mercedes may have a small 1-cubic-centimeter pocket in the spark plug area connected through a small channel. During static tests, this channel remains open to pass the test, but at higher racing temperatures, a pressure valve closes, increasing the ratio.

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

This would violate the cubic capacity limits no?

Not if the engine is 1599cc at operating temp.

1594, but point taken.

[zeffman]

A special pocket would be obvious in the CAD drawings submitted to the FIA. If it exists at all then it must be something incidental, rather than a primary mechanism.

I wonder if it is something to do with piston rings. When cold, they could let some pressure past but when hot they might form a better seal, raising the CR. If the expansion is longitudinal (around the circumference of the piston) then such expansion may be more significant, and less obvious, than if it was just a bulging pocket.

[Tommy Cookers]

the CR isn't a pressure ratio - it's a volume ratio
the ratio of cylinder swept volume to combustion chamber volume

and there's 120 years of precedent legally supporting the presumption that it's at room temperature in a static engine

[Hoffman900]

A special pocket would be obvious in the CAD drawings submitted to the FIA. If it exists at all then it must be something incidental, rather than a primary mechanism.

I wonder if it is something to do with piston rings. When cold, they could let some pressure past but when hot they might form a better seal, raising the CR. If the expansion is longitudinal (around the circumference of the piston) then such expansion may be more significant, and less obvious, than if it was just a bulging pocket.

That’s not how compression ratio works or is measured.

All rings work better under fire. All your modern low tension piston rings used in racing engines need cylinder pressure and crankcase vacuum to seal better.

[FW17]

This would violate the cubic capacity limits no?

Not if the engine is 1599cc at operating temp.

1594, but point taken.

1600cc (+0/−10cc)

[vorticism]

AMUS has an article suggesting Mercedes may have a small 1-cubic-centimeter pocket in the spark plug area connected through a small channel. During static tests, this channel remains open to pass the test, but at higher racing temperatures, a pressure valve closes, increasing the ratio.

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

This would violate the cubic capacity limits no?

The FIA defines the cubic capacity as the swept volume of the pistons, which means the volume of the combustion chamber (volume between the piston face and the cylinder head at TDC) is free.

[kptaylor]

the CR isn't a pressure ratio - it's a volume ratio
the ratio of cylinder swept volume to combustion chamber volume

and there's 120 years of precedent legally supporting the presumption that it's at room temperature in a static engine

And yet the regs didn't state this until the change in October... Is there actually a "legal" precedent regarding CR in F1?

[koolway]

Yes, but this document is not public.
But, everything points to ambiant temperature measurements.

[LM10]

In the end, what’s important is what the intention of the rule is. This is a thing in legal systems worldwide. If you go to court with a case with not so clear wording of a rule and two parties interpreting it differently, the judge’s job will be to find out the purpose of said rule.

Let’s say a judge asks the FIA what their intention was when writing “No cylinder of the engine may have a geometric compression ratio higher than 16.0”. What will they say? That the intention was to actually limit the PUs to this ratio (with acceptance of divergence due to thermal expansion) or rather that the figure of 16.0 was picked out of a hat and teams can do whatever they want?

[koolway]

At least quote the exact wording of the rule and don’t cut the bottom 2/3 that explain what they mean by 16:0

C5.4.3 No cylinder of the engine may have a geometric compression ratio higher than 16.0. The procedure to measure this value will be detailed by each PU Manufacturer according to the Guidance Document FIA-F1-DOC-C042 and executed at ambient temperature. This procedure must be approved by the FIA Technical Department and included in the PU Manufacturer homologation
dossier.

[LM10]

At least quote the exact wording of the rule and don’t cut the bottom 2/3 that explain what they mean by 16:0

C5.4.3 No cylinder of the engine may have a geometric compression ratio higher than 16.0. The procedure to measure this value will be detailed by each PU Manufacturer according to the Guidance Document FIA-F1-DOC-C042 and executed at ambient temperature. This procedure must be approved by the FIA Technical Department and included in the PU Manufacturer homologation
dossier.

No need for that part. The focus is on the limit. That’s why I cut it, obviously.

The intention of limiting the compression ratio stays the same and the fact that this is measured at ambient temperature - like it has been done for the last 1 million years as mentioned a billion times here - does not change this.

Under normal circumstances this should be an easy case in court. Every judge would tell you that the limit is there for a reason. That it was reduced from last year to this year further underlines the intention.

[slinger]

The objective and intension has been achieved. The compression ratio has been reduced from 18 to 16, under the standard measurement requirements. There by also reducing ,by assumption ,the compression ratio in the active engine while at racing stress levels.

[hollus]

No need for that part. The focus is on the limit. That’s why I cut it, obviously.

Please discuss in god faith. YOUR focus in on the limit, and selective quoting is a nasty, nasty thing. For many people the focus in on the limit and how it is measured adn monitored. You can disagree, but do not pretend to ignore the existance of that point of view.

The intention of limiting the compression ratio stays the same and the fact that this is measured at ambient temperature - like it has been done for the last 1 million years as mentioned a billion times here - does not change this.

Agreed. So effective C.R. will be lower in 2026 than in 2025. All seems in order, at least to some posters. The effective C.R. will not get 2 "units" smaller than in 2025, so I can also see why it does not seem in order to others.

Under normal circumstances this should be an easy case in court. Every judge would tell you that the limit is there for a reason.

The limit is there to limit things. That it does. Exactly what the limit is is the point of discussion.

That it was reduced from last year to this year further underlines the intention.

That has no logic. It is an arbitrary limit. It was arbitrary last year and it is arbitrary this year. That intention is only in your head. It is not more limit in 2026 than in 2025 because it is shiny new and a different number. The weight limit also changed, it gives it no more weight (pun intended) in 2026 then it did in 2025.

<And now with my mod hat on: Argue your point all you want, but argue it in good faith. As a minimum, you should be able to see and acknowledge the point that the other side is arguing. You don't have to agree with it, or course, and that runs both ways, but see it.
Ignoring the existance of that point, is not discussion. It is also extremely irritating to others.
Shouting your point louder and more often is not discussion, it is just shouting.
Selective quoting is not discussion, is dirty play.
Please discuss in good faith. Ideally discuss to learn or to teach, not to win. Keep it civil, no nasty discussion tricks.>

[hollus]

I will repeat and refine a question that goes unansweredfor some reason:

Do we realy believe that all teams were below 18:1 at all times in 2025?
Do we really believe that all engines were between 1590 cc and 1600 cc at all times in 2025?
It is a rethorical question,of course, don't answer it,but if you continue to argue that reaching 17:1 in 2026 would be a scandal as large as gambling in Sam's bar in Casablanca, then, please, do answer it.

I do though agree that the rewording in october is massively suspicious.