Weight Vs. Economy - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

CommodAnt · 09-01-2021, 06:55 PM

Quote:

Originally Posted by Isaac Zachary

If you're going up and down hills I find something similar in my Avalon and other vehicles I have driven. I can get similar or even better fuel mileage going over mountain passes than on flat highways even though that means I'm at a much higher throttle going up the mountains and then releasing a lot of it back into the atmosphere as heat as I engine and friction brake going down the other side.

PS. Regen braking in the Avalon does help some, but on most passes the battery fills up very quickly leaving me with normal engine and friction braking the rest of the slope. I also have noticed similar results in non-hybrids.

I think what happens is that it's similar to pulse and gliding. Engines are generally much more powerful than needed and so tend to run in a less efficient load on flat ground. But going to a slope puts the load at a higher, more efficient range.

In your caae you may not have the 5-8% grade passes that go on for miles and miles. But by adding more weight you get more of the effect, especially if the downhill portions aren't enough to merit braking letting you use the built up kinetic energy.

Interesting. I've spent some time living in the mountains and fuel economy was shocking (which is the opposite of what I expected). Having said that, they were significant inclines and declines. I think you are right though, you want to get inclines that are optimally steep, with declines that are just about right to keep you from needing to apply the brakes.

I think I'm going to need to do some experimentation here with some big tubs of water in the vehicle!

CommodAnt · 09-01-2021, 06:58 PM

Quote:

Originally Posted by aerohead

1) the answer is hiding in plain view.
2) the vehicle's inefficiency is during transient loads.
3) the longer highway drives keep throttling to a minimum, and the gearing keeps the engine close to it's brake-specific-fuel-consumption optimum.
4) if you could drive continuously at 35-40-mph around town, never stopping until you arrived at your destination, you'd see your highest-possible mpg.
5) AeroStealth's 2014 F-150 will do 22-mpg @ 62-mph (100-km/h ).
6) Same truck @ a constant 35-mph = 32-mpg.

Thanks, but perhaps I need to clarify my question a little.

I see better economy on long trips when carrying a heavier load than I see on long trips carrying little load. Thus, the variable is not the speed or acceleration/deceleration, but the mass of the vehicle. These observations in in conflict with advice to keep vehicle loads low (which is certainly valid in stop-go city driving).

Cheers.

cRiPpLe_rOoStEr · 09-01-2021, 07:20 PM

Quote:

Originally Posted by CommodAnt

I've spent some time living in the mountains and fuel economy was shocking (which is the opposite of what I expected). Having said that, they were significant inclines and declines.

What did you expect, and how do you believe some environmental conditions affected the fuel economy in the mountains?

Quote:

you want to get inclines that are optimally steep, with declines that are just about right to keep you from needing to apply the brakes

I noticed it in my neighborhood, while walking the dog. Most of the streets are one-way, and even though most of the uphill ones were already very steep, the downhill ones tended to be a little steeper.

CommodAnt · 09-01-2021, 07:42 PM

Quote:

Originally Posted by cRiPpLe_rOoStEr

What did you expect, and how do you believe some environmental conditions affected the fuel economy in the mountains?

I noticed it in my neighborhood, while walking the dog. Most of the streets are one-way, and even though most of the uphill ones were already very steep, the downhill ones tended to be a little steeper.

Need to switch the direction of those streets!