I'm not believing the 2020 is correct.
Based on everything I know, it will be a dished piston like a diesel with a spike in the center. This is something Audi played around with back in the Audi diesel LMP engine days and apparently had a significant effect on fuel consumption (documented in RET Issue 100). Wazari here has likened the Honda piston shape to Mt. Fuji with a little crater in the center spike. Put as much stock into that as you want.
Pat Symonds in
also refers to it as "omega piston bowls".
Some other takeaways:
* Thermal Efficiency of 52%
* BSFC 167gms/kw-hr (0.27lbs/hp-hr), occurs at peak power
* 800bhp from 1.6L (then another ~200hp or so from the hybrid unit)
* Lambda 1.3-1.4. Compare that to the DI / spark plug Audi DTM engine which runs at Lambda 1.15-1.38
* Rules limited 18:1 geometric compression ratio. All are at max
* Spark assisted HCCI, which Honda pretty much showed (earlier in the thread)
* They are Miller Cycle engines, with IVC before BDC
* Separate oil circuit for piston oil jets that runs cooler than the other circuits
* Miller Cycle requires very aggressive intake valve opening / closing designs and a lot of boost
* Valve angles low (5-7*), obviously done for squish geometry
* "Omega" piston bowls. Illustration in video helps visualize that
* Modeling from the FIA shows around 5.5bar boost (~80psi or so) and 50% mass fraction burn by 8* ATDC. Lose 1-2% of MFB in the prechamber. Quick combustion from 2-80% MFB and a slowing combustion beyond that. This final 20% with slowing combustion speed is where knock can occur.
The Audi diesel prototypes were also a fuel limited formula, Miller Cycle, and had similar rapid combustion concepts... all a decade plus ago! The F1 engines are essentially spark assisted TJI / HCCI / hybrid diesel like engines.