Tommy Cookers wrote: ↑30 Nov 2018, 12:55
godlameroso wrote: ↑30 Nov 2018, 07:04
Prechamber or not, flame out would happen somewhere around 1.6, so for gasoline that would be a practical limit....
would conventional ignition allow F1 to run at 1.6 lambda ?
afaik we know Honda has road engines on road fuel that (with PI and preheat) run homogeneously at 2 lambda
and F1 fuel is presumably optimised for combustion qualities
don't people think that TJI-type combustion allows leaner combustion ?
or do they think it is only used for faster initiation of combustion ?
design cooling capacity surely means F1 can sustainably run sub-optimal leanness only with lower MAP than is available
yes I have suggested that briefly running less lean at max fuel rate is intended and used
given that high MAPs/exhaust pressures don't yield greater turbine recovery
Some information I know is correct.
Spark ignition only viable to lambda ~1.4 at best, above that it's about TJI or controlled auto ignition, CAI/HCCI/GDCI. TJI gives optimal TE at 1.85 in tested engines and various RCM rigs, rapid compression machines. Lean limit close to 3 with prechamber scavenging using air, ~2.6 without due some exhaust gas residuals in pre chambers.
Given the McLaren ECU predates TJI in racing and really works best using closed loop control with models, feed forward, computationally efficient hack the map not really needed with today's compute power, works well and optimised. Given they're likely using Kistler piezoelectric pressure sensing in cylinders as a exotic knock/boost sensing first knock could take them out.
Suspect surface volume ratio could have some effect on Lambda lean limit, heat loss to surfaces so the baby 266cc cylinders would be disadvantage here to the typical experience with larger cylinders.
Due to the chemistry needing to happen, SI & TJI both achieve near identical times for 0-5% fuel mass fraction burned, after this burning rate is far faster in TJI.
Hot partially burned chemistry products,radicals,etc, extinguished as they pass through orifices of prechamber is the high ignition energy advantage of TJI the included turbulence enhancement also.
Hope this information helps.