I don't think there is a seperate oil combustion in the Honda engine. There is no evidence showing that and a seperate system wouldn't help because of the space problem.
Regarding the lower harvesting potential, I didn't read all posts here but I can help you with that:
The amont of air going through the turbine is only depending on engine speed, volumetric effiency (also controlled by throttle) and the Lambda. During combustion, no mass is lost or added by any reaction, this is simply impossible and will never be possible.
Calculation is like that:
MASSair = (displacement) * (engine speed) * (absolute boost pressure) * (normal air density) / 2
MASSgasoline = (MASSair) / (AF-ratio)
MASSturbine = MASSair + MASSgasoline
While having a more leaner combustion will give you a higher mass output at the turbine , you won't gain any harvesting potential. Yes, the power is higher, but you have to remember that the compressor size also has to increase and with that the power losses into the compressor.
Also, a higher ratio than needed will only give you a bigger turbine and compressor which isn't good for compactness at all, no matter where they are positioned. Since the efficiency is never at a maximum, both on compressor and turbine side, you want to keep these things not unneccesarily big.
Also remember: increasing the pressure of the exhaust gases with leaner combustion doesn't have any positive effect besides mostly compensating the bigger power losses of the compressor. Just remember: The amount of heating transfering to the air in the chamber will always be the same. if you just have more air, the air in the chamber won't heat up as much as before.
Now to the part of the harvesting. The potential is bigger on a normal combustion engine because of the slower combustion. This way, the time to transfer energy to the cylinder walls and not into the gas is lower and you have more pressure because the combustion isn't running as fast as before, therefor cooling of later.
When using something like TJI, you have a effect that is very much comparable to HCCI combustion. The pressure in the cylinder rises dramatically faster than before becuase combustion is finished much earlier. Now, you have a longer time with hot gases wanting to expand and loose their energy in the cylinder than before and the transfer of heat to the walls happens more intensively, thus the energy efficiency of the ICE gets much higher, while the energy that is left in the exhaust gases get's lower.
I hope you all could understand that
