A consumption map or efficiency map[1] is a chart that displays the brake-specific fuel consumption of an internal combustion engine at a given rotational speed and mean effective pressure, in grams per kilowatt-hour (g/kWh).
The map contains each possible condition combining rotational speed and mean effective pressure. The contour lines show brake-specific fuel consumption, indicating the areas of the speed/load regime where an engine is more or less efficient.
A typical rotation power output, P (linear to
pe ⋅ \omega
Overall thermal efficiency can depend on the fuel used; diesel and gasoline engines can reach up to 210 g/kWh and about 40% efficiency. Natural gas can yield an overall efficiency of about 200 g/kWh.[2] Average fuel consumption values are 160–180 g/kWh for slower two-stroke diesel cargo ship engines using fuel oil, reaching up to 55% efficiency at 300 rpm; 195–210 g/kWh for turbodiesel passenger cars; 195–225 g/kWh for trucks; and 250–350 g/kWh for naturally aspirated Otto cycle gasoline passenger cars.[3]