Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

kgwedi · 08-10-2010, 01:10 PM

I do P&G (engine off coasting) with my Chevy Metro. I have a fuel injector cut off switch to stop all fuel while coasting.
I see P&G from an energy point of view. Accelerating increases your Kinetic energy by using the Potential energy in your fuel. Coasting uses that Kinetic energy to overcome drag and friction.

I see hills as a good thing, because they trade the Potential energy in the fuel for an equivalent increase in Potential energy from the increase in height. Whether you use the energy in the fuel to accelerate, or go up a hill, there is still the same amount of energy transfered. Going downhill changes that Potential energy into Kinetic energy to overcome drag and friction.

Also the same thinking goes for stop lights when there is no traffic to force your speed. The energy I use to accelerate is used while coasting to the next light. I plan on arriving at the next light at the minimum speed so if it is a Red light I just sit and wait for green, when I'll start the engine and accelerate again. In my town I accelerate to a speed that will let me coast engine off just to the next light.
My city mpg is in the high/mid 50's and my back road long distance mpg is in the high 50's. What really hurts is slow creeping freeways.

Does this make sense to anyone?

08-10-2010, 01:10 PM	#1 (permalink)
kgwedi EcoModding Lurker Join Date: Jul 2010 Location: Eden Texas Posts: 37 Atos - '05 Hyundai Atos Prime AT 90 day: 21.33 mpg (US) Thanks: 2 Thanked 12 Times in 7 Posts	Hills are a good thing. I do P&G (engine off coasting) with my Chevy Metro. I have a fuel injector cut off switch to stop all fuel while coasting. I see P&G from an energy point of view. Accelerating increases your Kinetic energy by using the Potential energy in your fuel. Coasting uses that Kinetic energy to overcome drag and friction. I see hills as a good thing, because they trade the Potential energy in the fuel for an equivalent increase in Potential energy from the increase in height. Whether you use the energy in the fuel to accelerate, or go up a hill, there is still the same amount of energy transfered. Going downhill changes that Potential energy into Kinetic energy to overcome drag and friction. Also the same thinking goes for stop lights when there is no traffic to force your speed. The energy I use to accelerate is used while coasting to the next light. I plan on arriving at the next light at the minimum speed so if it is a Red light I just sit and wait for green, when I'll start the engine and accelerate again. In my town I accelerate to a speed that will let me coast engine off just to the next light. My city mpg is in the high/mid 50's and my back road long distance mpg is in the high 50's. What really hurts is slow creeping freeways. Does this make sense to anyone?