gruntguru wrote:Tommy Cookers wrote:
but boosted TJI engines seem to have more potential for lean running (than N/A engines)
What is your basis for that? Certainly boosted engines are more likely to benefit from detonation suppression but a NA engine with very high CR would be a good candidate. (I suppose such engines are not out there waiting for TJI to be added so researchers are limited to increasing CR on an existing engine - the result being a sub-optimal combustion chamber shape.)
N/A lean (to this extent) running means the engine is unnecessarily big for its power, relative to the boosted equivalent
(unless only part-time lean run, but this then needs NOx treatment)
that's why we have this F1, because of the potential of boosted SI full-time lean running
such engines are in production for use with gas fuel and correspondingly higher AFR
the traditional need for lowered CR with boost has effectively gone (because of the great dilution of heat)
boosted CR is as high as is useful or useable and the mechanical efficiency is higher
and one could from some of the numerous research papers form an impression that the boosted engine can be run leaner
btw - people forget that some engines have been made throttled at full power so that CR can be higher than otherwise
power control being of course initially by leaning and opening the throttle, this then followed by conventional throttling
Honda must have tried this
btw - a compound piston engine .....
with a small HP stage burning a super-rich liquid fuel mixture exhausting gas with high methane and CO content ...
could with additional air burn this gas in a larger LP stage at greater AFR than possible with liquid fuel
a higher-aromatic fuel (eg European-market gasoline) would be best at this (stripping carbon from gasoline to make methane and more CO)
