Conclusions of 104 identical runs. Fuel Economy Vs Average Speed

Hi Everyone

I am collecting OBD data from my Prius using an ELM327 Bluetooth connected to a Pocket PC (HTC HD) running OBDGauge freeware.

My Prius is a 2010 European version loaded with every available option but LKA, which is not available in my country.

I have recorded 104 identical runs starting and ending at the same parking places and following identical tracks, so I can prepare graphics and reach some conclusions. The runs are 10.0 miles (16.2Km) with the ending point 90 feet (28m) below starting point. 62% is highway and 38% is city.

This is the graphic of Fuel Economy versus Average Speed for the full run:



See the same graphic with metric units in the next post.

In my run there are 6 sectors clearly defined. Sector 1 is 100ft inside the parking lot, which is not interesting because I usually move in EV. Sector 2 is in the city with stoplights and my Prius is warming up. The graphic for Sector 2 is:



Sector 3 is still in the city, but has no stoplights so I never stop. The graphic for Sector 3 is:



Sector 4 is all highway with a big downslope, so the final point is 230ft below the starting point of this sector. The graphic is:



Sector 5 is also highway, but speed is limited to 50mph; it is almost flat. The graphic for this sector is:



These are my conclusions:

* In all sectors but sector 2 (city with stoplights) the lower the speed the higher the fuel economy (3-24 mpg higher for 10mph lower)

* In sector 2 (city with stoplights) it is reversed; fuel economy improves with average speed. I think it is related to the number of stops made on the run, so my conclusion is: in city traffic the more stops the lower fuel economy.

I hope you find this post interesting.

Hugs from Frank

 

Hi again. This post has the same graphics of the previous one but this time in metric units (Graphic titles in Spanish, sorry).

I am collecting OBD data from my Prius using an ELM327 Bluetooth connected to a Pocket PC (HTC HD) running OBDGauge freeware.

My Prius is a 2010 European version loaded with every available option but LKA, which is not available in my country.

I have recorded 104 identical runs starting and ending at the same parking places and following identical tracks, so I can prepare graphics and reach some conclusions. The runs are 10.0 miles (16.2Km) with the ending point 90 feet (28m) below starting point. 62% is highway and 38% is city.

This is the graphic of Fuel Economy versus Average Speed for the full run:



In my run there are 6 sectors clearly defined. Sector 1 is 30m inside the parking lot, which is not interesting because I usually move in EV. Sector 2 is in the city with stoplights and my Prius is warming up. The graphic for Sector 2 is:



Sector 3 is still in the city, but has no stoplights so I never stop. The graphic for Sector 3 is:



Sector 4 is all highway with a big downslope, so the final point is 70m below the starting point of this sector. The graphic is:



Sector 5 is also highway, but speed is limited to 80Km/h; it is almost flat. The graphic for this sector is:



These are my conclusions:

* In all sectors but sector 2 (city with stoplights) the lower the speed the higher the fuel economy (0.1-0.5 lower l/100 for 10Km/h lower)

* In sector 2 (city with stoplights) it is reversed, fuel economy improves with average speed. I think it is related to the number of stops made on the run, so my conclusion is: in city traffic the more stops the lower fuel economy.

I hope you find this post interesting.

Hugs from Frank

 

Hi bisco and thanks for your comments.

Highway mileage is very high in my runs because both highway sectors (#4 and #5) have very favorable conditions:

* Sector #4 has a big downslope and fuel injection is shut down for 1 to 1.5 miles depending of my driving and how heavy is the traffic.

* Sector #5 is almost flat but starts with the car at around 45mph (70Km/h) and finishes with car at about 10mph (15Km/h) The final deceleration lasts for half a mile using kinetic energy and no gasoline is burned.

By contrast, FE is miserable in Sector #2 with average figures in the low 30's because it has unfavorable conditions: warming up, traffic lights and upslope.

Hugs from Frank

 

Hi macman408

You are right, but look into the future: let me put hundreds of points of more runs and assume that you could find a lot of runs with same conditions: initial coolant temperature, ambient air temperature, initial speed, final speed, initial battery load and the only difference between all of them is average speed; drawing a regression line for these points makes sense. I am anticipating that future regression line although it does not make sense now with only 104 scattered points.

Hugs from Frank