Quote:
|
Originally Posted by ken1784
I'm second to Bob on this thread.
There was a discussion at PriusChat...
http://priuschat.com/index.php?showtopic=19543&st=120
I believe nbalthaser@Greenhybrid is same as nielb@PriusChat. 
FYI...
Following is my collected data of NHW-20 Prius driving highway with CC set at 91km/h(actual was 85 km/h).
Code:
section km mileage alt change
28km 24.5km/L 127m
15km 18.7km/L 248m
62km 40.8km/L -663m
Saw such various mileage results even on constant speed.
The reason was the altitude change on each sections.
If we use 0.106L/100m fuel to cover the potential energy, the table becomes as follows;
Code:
section km fuel used fuel pot fuel adj mileage
28km 1.14L -0.13L 1.01L 27.8km/L
15km 0.80L -0.26L 0.54L 27.8km/L
62km 1.52L 0.70L 2.22L 27.9km/L
Now, we can see constant about 27.8km/L mileage number for a virtual flat road.
The 0.106L/100m means...
34.6MJ/L * 0.106L = 3.67MJ consumed.
The mgh = 1350kg * 9.8 * 100m / 1000000 = 1.32MJ potential energy.
The tank to wheel efficiency is (1.32/3.67)*100=36.1%
We have following data on another vehicle...
1300kg NHW-11 Prius consumes 0.125L/100m ... 29.5%
900kg Honda Insight MT5 consumes 0.0823L/100m ... 30.9% |
This is brilliant! I would never have thought to approach the problem this way! Very, very clever!
Please correct me if I'm wrong but what Ken is showing is how to use the altitude changes and fuel consumed to figure out the fuel-to-wheel efficiency. So let me explain the approach.
1) Take at least three benchmark measurements with altitude changes at a constant speed to measure the fuel consumption.
2) Solve the simultanious equations to find the fuel consumption per altitude change (100 m)
3) Based upon the energy per unit of fuel, calculate the chemical energy per (100 m) of altitude change.
4) Based upon the vehicle weight, calculate the potential energy per (100 m) of altitude change.
5) The ratio of the two is the vehicle tank-to-wheel efficiency.
For my fellow Marines, he is measuring how much grunt it takes to go up a hill versus how much it should take.
Bob Wilson