|
By downsizing I refer to newer vehicles, from the sub 1L 2 cylinder twin air engine being put in the new Fiats replacing a range of 1.2-1.4L engines to the 1.4L turbocharged engine in the cuze replacing a 1.8L na engine, as well as the turbocharged 2.0L ecoboost engine placed as an available option in the 4000+lb unitbody Explorer.
There are at least four critical efficiencies in the otto cycle engine:
η0=f(ηv ,ηc ,ηth,ηm ) (overall efficiency)
ηv – Volumetric Efficiency
ηc – Combustion Efficiency
ηth – Thermal Efficiency
ηm – Mechanical Efficiency
ηv=actuall mass flowrate of air / the theoretical massflow rate of an ideal engine of a given displacement
Therefore:
ηv= actual massflow rate of air/ (density*displacement*rpm)/(Z) Z is 2 for 4 stroke engines 1 for 2 stroke engines.
Direct injection as compared to port fuel injection can improve VE by around 8%
Gaseous fuels ( e.g. H2) displace more than liquid fuels
The pumping losses increase at part open throttle, (hence the greater vacuum pressure ie pressure differential). Yes by increasing the power output can be considered as one type of loading, that's speeding up the rate of combustion and reducing the pumping losses proportionally to how far open the throttle is. Most common rail diesels and some direct injected gasoline engines are eliminating the throttle plate and their "gas" pedal controls the rate of fuel injection directly rather than indirectly though the quantity of air inducted into the engine.
This can be seen in the chart I attached (it is however a bit fuzzy because the original pdf was too large)
|