2026 Drama: Alleged engine loophole

[Stu]

Anyone given any thought as to how the check @ 130C is going to be quantified ? Whats the tolerance on that temp level ? How is it maintained and measured ? Are the instruments of measurement also heated ? Do the have complicity a calibrated norm ? At what temperature would the measurement tools conform with their reference ? What is the reference used for this process ? Can it be reliably repeated on demand ?

That asks more questions than gives answers.

^^this^^
This creates a whole world of ‘legal’ arguments. Anyone that was around when Ferrari appealed a DSQ back in the late 90’s /early 00’s about how their barge boards were legal “depending upon how you looked at them” will see how it is possible to drive a bus through hot testing results.

[upsidedowntoast]

If compression ratio decreases usually I dont see why this isnt the case. Didn't you give a good explanation yourself that this can happen simply based on thermal expansion when I asked for a clarification on dropping from 16 to 15.2 being more than 5%?

Of course it could be the case that the engine manufacturers have better material scientists at the end of the day that doesnt allow such a drop but I would be surprised if it didnt... there's no reason to create a huge story otherwise (imo).

It's likely that the other manufacturers have done work specifically to maintain a 16:1 compression ratio where it otherwise normally drop. It's just what they would do as engineers. Hodgkinson said everyone knows about thermal expansion and would be aiming for just under 16:1.

The huge story was that Mercedes went above 16:1.

I remember that defensive Hodgkinson interview. You could be right and whatever I am reading online might be wrong. We will know either way in a week the advantage Mercedes carries. I suspect its a lot. But let's hope I am wrong.

What was this interview?

If I recall correctly most other manufacturers could expect their PU to be 16:1 at ambient, down to 15.8 or 15.9 at operating. Meanwhile Mercedes went from 16:1 at ambient, up to 16.3:1 at operating. After accounting for noise that would be an advantage of single digit horsepower, maybe 5-10 up until June 1, then down to 2-3 until 2027, which is in line what Wolff was claiming.

The longer this goes on the more it feels like a giant nothingburger to me, similar to the flexiwing debacle. If it really was a 2014-level advantage that they were hiding, there would actually be lawsuits and bribery going on. Not to mention going from 18:1 down to 16:1 would completely mess up their aero and fuel and god knows what else.

[PlatinumZealot]

It is a nothing burger.

If Mercedes had the micro-hole might as well they have a 18:1 compression ratio, and it doesn't matter what tempersture the CR is measured at, it will beat the system. And doing that would break the spirit of the rules. This is why I don't think they are doing it.

[LM10]

It is a nothing burger.

If Mercedes had the micro-hole might as well they have a 18:1 compression ratio, and it doesn't matter what tempersture the CR is measured at, it will beat the system. And doing that would break the spirit of the rules. This is why I don't think they are doing it.

Because Mercedes is known for caring for the spirit of the rules?

[Arcanum]

None of the teams do. Ferrari's monkey grill doesn't comply with the spirit of the rules around exhaust blown aero. Yet the FIA changed the dimensions of the permitted aero around the monkey grill multiple times, up until December 2025, to allow Ferrari to build it. All the teams have exploited flexi wings over the years.

There are the rules, and there are the tests for the rules. The goal for every team is to pass the tests.

[SB15]

It is a nothing burger.

If Mercedes had the micro-hole might as well they have a 18:1 compression ratio, and it doesn't matter what tempersture the CR is measured at, it will beat the system. And doing that would break the spirit of the rules. This is why I don't think they are doing it.

Because Mercedes is known for caring for the spirit of the rules?

You say it like other teams are innocent saints lmao

[basti313]

Noob Q : the CAD drawings can be used to calculate geometric compression ratio. What 'temperature' is the CAD drawing meant for ?

I thought that was explained several times? You design, manufacture and measure/verify at the usual ISO, SAE or whatever norms, which have a defined ambient temperature. Anything else does not work.
This is the previous "ambient" check.

Anyone given any thought as to how the check @ 130C is going to be quantified ? Whats the tolerance on that temp level ? How is it maintained and measured ? Are the instruments of measurement also heated ? Do the have complicity a calibrated norm ? At what temperature would the measurement tools conform with their reference ? What is the reference used for this process ? Can it be reliably repeated on demand ?

That asks more questions than gives answers.

^^this^^
This creates a whole world of ‘legal’ arguments. Anyone that was around when Ferrari appealed a DSQ back in the late 90’s /early 00’s about how their barge boards were legal “depending upon how you looked at them” will see how it is possible to drive a bus through hot testing results.

I still think they will stay with CAD. As also CAD is equally for the ambient, the only really sensible test for CR in an environment and such a difficult engine like in F1. I still do not see anyone pouring liquid into a F1 engine trackside...and any dynamic tests would fail as they show effective CR, not geometric CR.
The most save test would be to define a FEM module, set it to 130°C and run it on all engines. As the teams define the CR measurement, I guess they will also define the FEM if this comes.

If I recall correctly most other manufacturers could expect their PU to be 16:1 at ambient, down to 15.8 or 15.9 at operating.

There is still the question how everything comes together. I am still calculation down to a worst case of closer to 15:1. The 15.9 calculation comes from a wrong assumption, that only the piston stroke plays a role. But in fact the whole length down to the crankshaft is relevant.

Because Mercedes is known for caring for the spirit of the rules?

You say it like other teams are innocent saints lmao

Funny conversation.

You might turn it around: If you are looking for a saint, maybe skip Toto

[Martin Keene]

There is an interesting piece by Pat Symonds in Autosport this month on this topic. He says the compression ration will drop as the engine heats up, and says an engine with a 16:1 ratio, will be more like 15.2/15.3:1 at operating temperature. This is because the aluminum block expands by more than the connecting rod, ~0.3mm for the block and 0.05mm for the rod.

He then speculated that by putting a particular grade of steel liner into the cylinder block, the expansion for the block could be reduced to 0.05mm and by changing to a austenitic stainless steel for the rod, that could offer an expansion greater than the block.

He then moved on to the weight of the rod, and with a limit of 350 grams for the con rod, you could make one from stainless and still hit the weight target.

[bluechris]

There is an interesting piece by Pat Symonds in Autosport this month on this topic. He says the compression ration will drop as the engine heats up, and says an engine with a 16:1 ratio, will be more like 15.2/15.3:1 at operating temperature. This is because the aluminum block expands by more than the connecting rod, ~0.3mm for the block and 0.05mm for the rod.

He then speculated that by putting a particular grade of steel liner into the cylinder block, the expansion for the block could be reduced to 0.05mm and by changing to a austenitic stainless steel for the rod, that could offer an expansion greater than the block.

He then moved on to the weight of the rod, and with a limit of 350 grams for the con rod, you could make one from stainless and still hit the weight target.

Do we know when they said that Ferrari used steel in the engine, where it was? maybe Ferrari doesnt has this much drop in hot conditions.

[Martin Keene]

That rumor was apparently a cylinder head, which I still really struggle to see the benefit of.

[AR3-GP]

That rumor was apparently a cylinder head, which I still really struggle to see the benefit of.

A steel head expands less than an aluminum head. This is relevant for discussion surrounding the loss of compression ratio at operating temperature. A steel head can also sustain a higher operating temperature without losing its stiffness. Higher operating temperature means less cooling and more thermal efficiency.

[bluechris]

That rumor was apparently a cylinder head, which I still really struggle to see the benefit of.

A steel head expands less than an aluminum head. This is relevant for discussion surrounding the loss of compression ratio at operating temperature. A steel head can also sustain a higher operating temperature without losing its stiffness. Higher operating temperature means less cooling and more thermal efficiency.

This is what i am trying to understant but i suppose noone knows. If this head is making the engine to loose less compression in normal working temperatures.

[richardn]

"The Mercedes engine has been measured by the FIA at both ambient and operating temperature and complied with the limit of 16:1 at all times, senior F1 insiders have told BBC Sport."

https://bbc.com/sport/formula1/articles/cq8g3lqqdvgo

If I was hypothetically designing a solution to design something to reduce the size of the compressed area in a cylinder. I'd be looking at a downward pointing conical aluminium section inside the steel surround in the piston, just under the crown. It gets really hot there and you get two axis of expansion which both force the aluminium upwards.

The hard bit isn't getting it to buckle upwards when it heats, it will be getting it to drop back into place when it cools.

Despite the hypocrisy, I can see the advantage of the hot only measurement regime. It simplifies the engine development (which is a stated FIA aim) and it would mean that any pockets of high expansion material would be automatically suspect for raising the ratio above 16:1.

[basti313]

That rumor was apparently a cylinder head, which I still really struggle to see the benefit of.

A steel head expands less than an aluminum head. This is relevant for discussion surrounding the loss of compression ratio at operating temperature. A steel head can also sustain a higher operating temperature without losing its stiffness. Higher operating temperature means less cooling and more thermal efficiency.

How much length should this add? This is neglectable vs the length of the rods. The issue is the different expansion between the Al block and the rods as these are long.

[FrukostScones]

My bad, 2014-2020.

2016, 2017, 2018 were fun.

For whom except MB followers?

2017, 2018 was fun for Ferrarifans. 2016 the year of the Britney.