AR3-GP wrote: ↑
Wed Mar 22, 2023 10:14 pm
Hoffman900 wrote: ↑
Wed Mar 22, 2023 10:08 pm
gruntguru wrote: ↑
Wed Mar 22, 2023 9:56 pm
Lots of similarity to diesel combustion but comparison fails on three counts.
- Compression ignition.
- Heat addition at constant pressure after TDC.
- Rate controlled combustion.
I think Honda’s video and statements suggest there is compression ignition.
It's probably a grey area that requires the compression ignition to occur after the spark ignition.
Technically the rules forbid pure compression ignition, although I'm not sure how one could prove that manufacturers were not just using a "token" spark ignition system that was firing incidentally...
In theory one could argue that any pressure rise occuring before the spark firing was a "loss of control"
Ferrari is quoted in a recent RET of using 5 injection events / a cycle. I can’t imagine the spark plug is firing 5 time either.
Honda’s video plus illustrations shows a flame propagating from the chamber / piston edges meeting a flame being dispersed from the jet in the roof of the combustion chamber centered over the piston.
Pat Symonds himself called them hybrid combustion concepts.
14:05 he has a slide too. He says they’re difficult to classify but calls them “spark assisted HCCI” which Honda’s video also shows.
In the context of Ferrari’s info, Honda’s information, and Pat’s statement, it’s fair to say they are using the injector to create a stratified or a homogenous charge in the combustion chamber before lighting off an additional charge of fuel in the TJI chamber, and likely using in-situ cylinder pressure sensors to control the timing of the spark plug so the TJI combustion event is timed with the homogenous or stratified charged combustion event.