Quote:
Originally Posted by cr45
This is incorrect.
There are 3 energy components involved in climbing a hill at constant speed.
1/ Gain in Potential Energy.
2/ Parasitic loss due to tyre rolling resistance.
3/ Parasitic loss due to aerodynamic drag.
As the aerodynamic drag is proportional to the square of the velocity then as the velocity increases the total energy required to overcome aerodynamic drag whilst climbing the hill also increases.
|
What I said was that climbing the hill requires the same amount of energy regardless of how fast you do it. Overcoming wind drag is a separate topic. That wind drag would exist regardless of the hill. Wind resistance and grade resistance are different factors and I was focusing on the topic of overcoming grade resistance.
Obviously if you encounter wind resistence while climbing the hill, you are going to burn more fuel. But the hill itself did not take more energy from the vehicle. That was the wind. Not the hill.
Quote:
Originally Posted by cr45
Small engine cars often have very little excess power when travelling at highway speeds up a hill. Any acceleration will cause fuel enrichment beyond stoich AFR and lead to poor mpg. Your argument is only applicable to vehicles with large engines relative to their mass.
Small engine cars.
|
Brake specific fuel consumption is still more efficient under heavy load, even with fuel enrichment. My "argument" is actually a fact that applies to all quantity-regulated spark-ignited gasoline engines. Do you know what BSFC is? It basically indicates how much work the engine will get done if you give it a certain amount of fuel.
If you supply an engine with one liter of gasoline, and set the engine to peak torque near WOT, it will do more work before running out of fuel than if you give the same engine the same amount of fuel and run it with low load.
For a while, I worked as a fuel systems engineer for a well known company that manufactures internal combustion engines. I'm still very much involved in engineering projects which have the sole intent of increasing the thermal efficiency of engines. Not everything regarding efficient operation is intuitive. I'm not saying to blindly accept what I'm saying, but I recommend you withhold conclusion on this topic and research more.