Tommy Cookers wrote:whatever the (relative) work done by whatever to get fresh charge into the engine past the valves
it's in recent years at an all-time low, the unprecedentedly high bore:stroke ratios allowing the biggest-ever valves (relatively)
helped also by gas valve springs, 7 speed instant-change paddle transmissions, and mapped power curve smoothing
the engines no longer needed a good spread of power that required compromised peak-rpm cylinder filling
bmep values at high rpm show cylinder filling corresponding not to a 1 bar atmosphere, rather to 1.2 bar
Increasing bore size has it's limits in terms of "quality" of geometry of the combustion chamber volume. You are speaking of volumetric efficiency and you are correct that with resonant tuning effects 120% was/is possible without turbo. Bear in mind that it is the huge valve overlap that helps achieve this VE.
I disagree with you on the diminished need for a good spread of power. That is always a nice thing to have and peaky engines are never winners. The optimization of combustion is usually a game of compromise to have minimum "missed cycles" due to poor mixture filling/preparation or poor combustion. Key to that is combustion chamber shape and charge delivery (some amount of swirl/tumble but not too much).
Tommy Cookers wrote:
this would suggest that the usual '1 bar' methods for calculating 2014 boost are pessimistic ?
though the 2014 engine will have relatively smaller valves, due to lower b:s ratio
'tuned length' exhaust may be as efficient (notwithstanding the turbo) than recent N/A systems designed for 'exhaust blowing'
True. The V6 will have significantly smaller total valve area to deliver and extract gases thru. I have not analyzed the b/s impact , but we could assume the compression ratio will be lower so the combustion chamber will have better geometry as compared with atmo V8. Inlet and exhaust system geometry and tuning will have the same general important impact as before, requiring some engineering design an tuning. Turbo or no turbo, the game is the same when you have compressible gases to deal with. Principles don't change, but details are different.
Tommy Cookers wrote:
N/A F1 fuel was not in recent years Octane-critical due to the very high rpm, Shell stated here around 95 Octane
what is undisputed is the recent waiving of the fuel Octane limit that was a key feature from 1958
never mind the efficiency claims on fuel of unlimited specific energy and Octane No, what would be the efficiency using road fuel ?
the efficiency benefits of this technology would anyway be less in road use ie at partial and low powers
though one maker seems to be giving it some publicity talk already
I am a bit weaker on the fuel subject, but can provide this.
For many years now, the operating temperatures inside of many formulas of racing engines are higher that 100 degC. The chemistry of all fluids used inside must conform and support those operational needs and that includes fuel.
With atmo V8 you needed fast evaporating and burning fuel while having a sufficient knock limit to deal with a less than ideal combustion chamber. Large bore and high compression ratio resulted in a large diameter and very flat combustion chamber where you had around 42-45mm distance (50% of the bore) between the spark plug and the extremity of the combustion chamber. This distance is an important design factor since the flame has to travel this distance each combustion cycle. In ICE combustion science, there exists a phenomena called "end gas" which is prematurely quenched yet still hot and only partially burned fuel/exhaust mixture meandering at the extreme crevices of the combustion chamber near the cylinder bore. This end gas is the primary source of knocking detonation.
With the V6, the bore will be smaller and compression ratio will be lower allowing for better combustion chamber geometry reducing this "end gas" effect and requiring less relative knock resistance from fuel. I say relative, because in this case we have boost so from another angle this fuel must be even more knock resistant than with V8. The octane number game is rather meaningless because fuel is optimized for the particular combustion configuration of the engine. I would say that if in 2014 you poured the gasoline used by Ferrari into a Mercedes engined car, the performance would be different and most likely worse or even damaging.
In terms of fuel for road cars, there is such disparity of chemical engineering applied that those two worlds are really apart. Sorry again for a lengthy reply.