atanatizante wrote: ↑11 Feb 2026, 23:04
Stu wrote: ↑11 Feb 2026, 13:05
WardenOfTheNorth wrote: ↑11 Feb 2026, 12:56
The talk about sensors, how would a sensor measure the geometric CR at racing temperatures?
It wouldn’t, but it would measure cylinder pressure.
THIS!!! This is the only solution: insert a sensor into the cylinder and set a maximum pressure value inside it. If this pressure limit is exceeded, the ECU reduces the fuel flow. This is the best compromise in this issue for all parties involved. And this can be done elegantly by issuing a TD, as has been done in the past (2022, for example), and no one has complained that the regulations are being violated. It is an effective, very inexpensive method that avoids the need to redesign the ICE, software, fuel, and so on. A single sensor coded and supplied by the FIA, and in addition, only a single line of code is entered into the ECU software...
Apart from the problem of peak cylinder pressure =/= compression ratio.
If I have an engine with a CR of 16:1 and I run a PCP of ~165 bar with 20 degrees of advanced ignition timing (all numbers picked at random), with a mechanically unchanged engine, if the ignition timing is advanced further, to say 22 or 23 degrees, the PCP *will* increase, to probably something like 168 bar because the burn of the mixture in the cylinder has started earlier in the cycle and starts in a bigger volume of space and as the engine rotates as normal that space will get smaller.
All of this without changing the mechanical geometry of the engine or the compression ratio.
I know they are boost pressure limited, but a boost pressure increase would do the same thing, again without a CR change. There are many many factors that effect PCP.