2026 Drama: Alleged engine loophole

[basti313]

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.

[venkyhere]

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.

Oh.
My.
God.

Didn't know the org which prescribes the 'formula' itself, doesn't have it's own method to determine engine compliance, and places so much 'trust' on the teams by only looking at CAD files. How naive is that ? Or probably the wrong word. Corrupt, rather.

[Hoffman900]

The issue is no one knows there is an actual issue and it’s all just hersay and for most, general ignorance of what compression ratio even is, or how strict interpretation is impossible in reality.

As for why I am repeating myself, 33 pages into this thread and people still can’t differentiate between compression ratio and cranking compression, even though it’s been explained numerous times.

This is mostly large corporate teams playing politics and getting their fans wound up. For content creators, it’s clicks.

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.

People /orgs threaten to sue other people / orgs all the time and rarely act on it because it won’t go anywhere in court. It’s also terrible publiclity.

Furthermore, teams jumping on it could be less about geometric compression and more about getting a peak behind the curtains of Merc’s PU during discovery, but again, no one is actually going to get sued.

The presumption that Audi has zero items / designs on their car that push the grey area is silly as well and that their car meets the letter of the rule book in every single way. That’s why no one will actually follow through on a lawsuit, because they’re all doing stuff that is “tech shed legal” but doesn’t meet the spirit of the rule. Mercedes knows this and will likely tell Audi “do it, I dare you”.

The FIA will make this go away because teams threatening to sue each other is a rather bad look.

[Hoffman900]

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.

Oh.
My.
God.

Didn't know the org which prescribes the 'formula' itself, doesn't have it's own method to determine engine compliance, and places so much 'trust' on the teams by only looking at CAD files. How naive is that ? Or probably the wrong word. Corrupt, rather.

The local redneck circle track is better prepared to check compression ratio…

[basti313]

Didn't know the org which prescribes the 'formula' itself, doesn't have it's own method to determine engine compliance, and places so much 'trust' on the teams by only looking at CAD files. How naive is that ? Or probably the wrong word. Corrupt, rather.

What is wrong with this? There is nothing more precise than measuring in CAD. The CAD files are the basis for the homologation.

The local redneck circle track is better prepared to check compression ratio…

No. That is the point with all this homologation. If anything is suspicious the engine goes on a CMM or gets checked on any suspicious things.

[hugobos]

Ambient is a very general term. I my line of work -power generation-you have a defined ambient temperature . Ussually 10 or 15 degrees celcius, including a defined barometric pressure. Then correction curves are calculated and validated for every ambient temperature, to determine power output and efficiency. Ambient temperature if not defined is useless.

[Hoffman900]

Didn't know the org which prescribes the 'formula' itself, doesn't have it's own method to determine engine compliance, and places so much 'trust' on the teams by only looking at CAD files. How naive is that ? Or probably the wrong word. Corrupt, rather.

What is wrong with this? There is nothing more precise than measuring in CAD. The CAD files are the basis for the homologation.

The local redneck circle track is better prepared to check compression ratio…

No. That is the point with all this homologation. If anything is suspicious the engine goes on a CMM or gets checked on any suspicious things.

Emphasis on “check”. By all means, it seems the FIA has no way to check it at the track.

Seeing how it’s a multi billion dollar sport run with volunteers and part timers, it’s not shocking.

[Hoffman900]

Ambient is a very general term. I my line of work -power generation-you have a defined ambient temperature . Ussually 10 or 15 degrees celcius, including a defined barometric pressure. Then correction curves are calculated and validated for every ambient temperature, to determine power output and efficiency. Ambient temperature if not defined is useless.

This. This is why any QA / QC room in aerospace and automotive / motorsports is climate controlled.

[FNTC]

Yeah, "ambient" without an actual value is very strange. It could be 5C on one track and 40+C on another.

[LM10]

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 limit having to be at 16.0 is a rule and that this is measured at ambient temperature is a scrutineering procedure.
Seems like other than Mercedes all other PU manufactures managed to interpret it this way.

Also I didn’t cut the quote in bad faith. It was posted and talked about multiple times here already. The majority of the people in this thread who have been discussing this topic for the last weeks should know the simple quote.
The literal purpose of my post was highlighting the rule in a juridical context.

I will appreciate if you don’t accuse me of bad faith or “nasty, nasty” acting next time. Thank you.

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.

It seems to be in order for all, but Mercedes.

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

The exact limit is in the rules. Though, I agree that due to simple physics it’s not written accurately.
But one thing I’m sure of is that the limit was not set to be exceeded significantly by spending tons of resources to build a PU with such specifics. Only one team did that. The odds are high they were the ones misinterpreting the rules.

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.

The limit was reduced to simplify Audi’s entry. This fact for itself should give a hint.

[gearboxtrouble]

It is pretty simple to me. Thermal expansion is a natural property of all engines and pushing this to increase compression at temperatures is logical and meets the rules without any trickery involved to make the engine legal. If anyone is boosting performance using just the thermal expansion of cylinders and rods then they should be allowed to race as is because they've just done a better job. A thermally isolated 1cc chamber on the other hand is a defeat device that can be used by an illegal engine to cheat the test. Without it the engine would exceed a 16 CR at ambient temp. This is blatantly cheating and in the same ballpark as manipulating the fuel flow sensors to boost power. I do not know what's really going on but if Mercedes was stupid enough to use the defeat device they need to be penalized because it's so obviously cheating. I know its impossible for them to change their internals by Melbourne but the FIA should cap their energy budget at say 2925 MJ/h (97.5% of everyone else) and allow them a later homologation deadline so that they can fix the engine if this is really whats happening.

[FrukostScones]

I agree.

[basti313]

Emphasis on “check”. By all means, it seems the FIA has no way to check it at the track.

Wrong thread for this. This is by all means a problem for the whole homologation and it seems every team involved is happy how it is done, was done since years.

Seeing how it’s a multi billion dollar sport run with volunteers and part timers, it’s not shocking.

Strange assumption.

This. This is why any QA / QC room in aerospace and automotive / motorsports is climate controlled.

This is not by accident, but by design in FIA very common. A rear wing needs to comply at 10°C in Vegas and at 30°C in Abu.
Furthermore I have never seen a big QMM machine being controlled to the last Degree...ours operate easily in a range of 20-25°C for aerospace and automotive...

For the engine this is anyways not problematic:

Ambient is a very general term.

No. There is still the ISO and SAE definitions, controlled work environments also kept by FIA in the 20 to 25°C range.
If a manufacturer would define that he wants to do the homologation at 26°C he would need a very good reason for this. Otherwise FIA would simply not accept this.
This is the nice thing: If they start something fishy in the measurements, FIA can say "no". This is much better than a rule with a fixed temp that would cost a lot of money.

[hugobos]

No. There is still the ISO and SAE definitions, controlled work environments also kept by FIA in the 20 to 25°C range.

Thats good and noteworthy information, i was hesitant to mention the ISO , was not sure if the FIA used it and could not find it. For my work it is the standard. Thank you!

[basti313]

No. There is still the ISO and SAE definitions, controlled work environments also kept by FIA in the 20 to 25°C range.

Thats good and noteworthy information, i was hesitant to mention the ISO , was not sure if the FIA used it and could not find it. For my work it is the standard. Thank you!

Well, not by the law, but as mentioned...if they start running a CMM for homologation at 30°C it would trigger good questions.