MFI special edition Motorsport technology details 2019-2020 reports Toyota TS050 hybrid powertrain.
https://www.as-books.jp/books/info.php?no=MFS20191227
https://www.as-books.jp/books/preview.php?no=7479 (preview)
Engine development
There were three weakness points in the Toyota 2015 spec engine.
1) Lack of competitiveness on high altitude circuits.
2) Slowdown of NA engine output improvement pace.
3) Lack of advantage in overtaking due to lack of low-speed torque.
Therefore, Toyota has determined that turbo engine is required.
To increase the theoretical thermal efficiency, it is necessary to raise the compression ratio and specific heat ratio.
Toyota was initially considering an L3 (inline 3 cylinder) engine for 2016 spec.
However, it was found that the load was too high and the strength was insufficient.
Therefore, Toyota examined a four-cylinder engine, and found that the strength was still insufficient.
(V4 was excluded for emotional, not technical, reasons.)
Then finally settled on a V6 2.4l engine. (Toyota was considering 2.1l V6 for 2017.)
When switching to V6 turbo, pendulum absorber was removed to reduce weight (3kg).
Toyota introduced pre-chamber ignition (PCI) in the 2017 spec.
It was a passive PCI with no injectors in the pre-chamber.
Toyota has developed an active pre-chamber as the 2019-20 spec, but has not entered the race due to development freeze.
The introduction of PCI increased the burning rate by 30%.