Here are some charts from a university course on
engine performance maps. They would be easier to understand if they had used real units.
As they point out, one cannot usually cruise at the peak rpm at the throttle setting for best BSFC as the engine will probably be putting out more power than the car or truck needs. The variable displacement engines attempt to allow the engine to run closer to peak efficiency at cruising speeds.
I've made a few attempts to find this information for engines of interest to stovebolters, vintage hot rodders, etc. IC engine textbooks also show examples, and SAE papers have some information, but nothing very interesting for a daily driver engine. Chevrolet must have generated this information for the 216-235-261 family but I have not stumbled upon it.
As they point out, one cannot usually cruise at the peak rpm at the throttle setting for best BSFC as the engine will probably be putting out more power than the car or truck needs.
Let me know if there are any questions. When i took an IC engine course back in 1965, we generated an engine performance map using a 265 SBG on an electric generator dyno. I seem to have lost the lab report. We generate similar types of plots for jet engines, but we use thrust instead of torque and horsepower.
Hoyt
