Shown below is the calculated engine power requirement for a European spec Mitsubishi Mirage 1.0 for 2 different operating conditions.
1/ flat road, constant 80 km/hr
2/ 5% gradient hill, constant 80 km/hr
It is evident from the BMEP of 9.21 that this engine is almost at full throttle climbing the hill.
Shown below is the 2 bmep values added to a bsfc map obtained from a similar engine.
It is evident that the engine is operating in the island of maximum efficiency whilst climbing the hill at constant velocity.
It makes no sense to go to WOT and have the sfc driven down from 240 g/kWhr to 280 g/kWhr.
Hence the concept that all cars should accelerate up hills is flawed!