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[The Toecutter]

I wonder if a diesel or electric would respond this way?

My hunch is that a diesel would, but an electric wouldn't. The losses for an electric drive tend to increase with load(P=(I^2)*R)

[GasSavers_Brock]

Originally Posted by The Toecutter

My hunch is that a diesel would, but an electric wouldn't. The losses for an electric drive tend to increase with load(P=(I^2)*R)

Not sure about all diesel?s, but my TDI uses no fuel coasting in gear down hill. At idle scangauge will show about .2L/hr once warm. If I am going down a hill in 5th with no throttle added it shows 0.0L/hr, if I push the clutch in it goes back up to .2L/hr.

So the big debate on the TDI forums is whether to coast in neutral or coasting in gear. Of course you slow down a lot sooner coasting in gear.

If I have to stop I have figured out how far out I can coast clutch in to make it just right, or if I am in traffic how far out I can coast clutch out, no throttle. From the testing I have done it is better to coast in neutral at .2L/hr then coasting in gear at .0L/hr because you have to stay of the throttle longer leading up to a coast in gear (assuming a flat run out).

Unless you have just the right hill to gain no speed in gear and have to slow down anyway, I use neutral.

[omgwtfbyobbq]

Originally Posted by Brock

Not sure about all diesel’s, but my TDI uses no fuel coasting in gear down hill. At idle scangauge will show about .2L/hr once warm. If I am going down a hill in 5th with no throttle added it shows 0.0L/hr, if I push the clutch in it goes back up to .2L/hr.

So the big debate on the TDI forums is whether to coast in neutral or coasting in gear. Of course you slow down a lot sooner coasting in gear.

Just compare it on a KE+PE/top to KE+PE/bottom basis (I'm guessing it depends on the hill). You can calculate the difference in energy between the car's initial state, higher up on the hill, and it's final state, lower down on the hill. Compare these initial states to find out which car, in gear/no fuel or out of gear/little fuel, gains more energy from rolling down the hill. Since the car out of gear is idling, calculate the energy used while idling multiplied by the appropriate modifier for diesel engine/transmission efficiency, and account for it including it in the car that's out of gear's delta E. You could test this on a few different hills to get a curve of best fit, and approximate the grade where it becomes better to keep it in gear, or coast in N, barring of course speed limits.