motobaleno wrote: ↑30 Dec 2025, 18:57
With a steel head is more diffcult to control knocking and maybe not useful to seek for increased CR
Context dependent. Steel is around one-fourth as thermally conductive as aluminum, but if the CC walls can be made f.e. one-third as thick then the latency between heating and cooling is reduced and also the total surface area exposed to coolant will increase compared to an Al head. If the head is forged then you could achieve wall thicknesses similar to the piston crown, or thinner. Forged steel + no reciprocating forces + full perimeter support + the benefit of liquid cooling that the piston does not have, should allow for some very thin heads. An unturned stone?
That article makes it sound like a steel head was developed in parallel for:
-Durability. Four engines per season. (with questionable results)
-Higher cylinder pressures (odd considering reduced boost & fuel, unless he meant the prev regs)
-Not for CR trickery (at least, it’s not mentioned)
If it relates to CR tricky:
Along with a steel block, with the goal being to achieve a relatively dimensionally stable block & head which a necessarily hotter conrod & piston could thermally expand into, to achieve an illegal compression ratio that cannot be confirmed exists except for by inference. If a tree falls in the forest, does it make a sound? None of this will be a secret to the other engine designers (I hope, at this level and budget) so if this approach is beneficial then everyone will show up with steel engines, having mutually agreed to keep the wording of the regulations as-is so that everyone can break the rule in unison. It would be upon the FIA to change the wording if they are unhappy with an engine arrangement that they know unavoidably breaks the rule. No one would want to lose R&D money on it, so, perhaps the FIA would allow it for one year before demanding that only aluminum be used for the block & heads.
As for higher thermal limits:
A section of a steel head could be made purposely thick to enhance convection latency so that a portion of the CC wall remains hot and acts like a hot bulb or glow plug in order to initiate ignitiion in addition to what the spark plug can supply. Only one spark is permitted per cycle (or maybe stroke, depending on the FIA’s unspoken definition of ‘cycle’ which is officially undefined), so any additional ignition features might be handy. F.e. a thin flange around the perimieter of the CC could remain always hot and ensure combustion at the periphery. These sort of tricks could not be done with Al, as it would melt. Might also be difficult to achieve in steel if it erodes too much during such opps.
If it relates to higher CR potential:
With less air, fuel, and in-cylinder compression available, only one spark, and no turbocompounding, where do you have left to go to optimize thermal & operating efficiency? Further development of combustion. There are numerous concepts which have been in developmen over the past couple of decades: HCCI, SPCCI, GDCI/PPC.
However. All of these could have been pursued in the previous regs. If new combustion concepts are being developed now and were not being developed before, a question would be: why? I have half a thought to suggest that turbocompounding as it existed may have been preventing new combustion development. If combustion and cycle efficiency are improved there will be less energy in the exhaust, yet a turbocompound needs waste heat & pressure to recuperatte--that’s the point of its existence, to return it to the ICE. In the new regs there is only a familiar TC, which could be though of as a pneumatically linked turbocompound (credit Tommy Cookers for that gem of a metaphor, and such a line of thought might help devise ways of managing lag in lieu of anti-lag), but its primary purpose is to convert exhaust energy into compressor work, and the total amount of work required to achieve necessary boost will reduce as combustion efficiency is improved. Correct?
Regardless, where can combustion concepts still go? Is it at all possible that peak cylinder pressure could be as high or higher in these regs (one of the vague suggestions in the article) despite there being less air and fuel in the cylinder and less geo compression. Maybe if further spark advancement, detonation or knock are put to use. With the total peak cylinder pressure across the piston/CC face may or may not be higher, but local to detonation fronts it will be, which is where the greater durability of steel could come into play.
) include the engine rpm & gear choice in the trace, it would be informative to check whether the changes in slope during the recharge phase is due to the gear changes or due to the algorithm itself
