MPG Experiment

[Gren71]

No resistance continues to go up as speed increases. Forever.

So at very high speeds the aerodynamic drag becomes an even larger percent of total drag.

If you look at my hand drawn graph you can see that at low speeds mechanical drag is higher. At a certain speed the graphs cross and from that point aerodynamic drag is the dominant drag component.

i appreciate it. I saw that on the graph, just wrapping my head around this stuff. I have a loose understanding of it so im enjoying learning as I go.

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[dcmdon]

i appreciate it. I saw that on the graph, just wrapping my head around this stuff. I have a loose understanding of it so im enjoying learning as I go.

You are clearly bright and disciplined. You will figure it out. Remember that Elon Musk does not have an engineering degree. Ha.

 

[Gren71]

I have so many tabs open reading about fluid dynamics and the equations, and related equations, and other stuff. haha what a fantastic rabbit hole.

 

[jeepin48]

If you want to look an mechanical drag it can help to break it down into tiny pieces. Tires for example have rolling resistance at the interface of the tire and the road. The small flat spot on the bottom of the tire is created by the rubber flexing. So to roll the tire has to climb that flat spot (drag) constantly regardless of speed. .... And I dont think a jeep can go fast enough to make a tire balloon.

You also mentioned the rotational inertia of the tire. That is stored energy and you get all of that back when you slow down. Yes it takes more energy to accelerate the more mass you have but it also carries you once you let off the pedal.

 

[Gren71]

If you want to look an mechanical drag it can help to break it down into tiny pieces. Tires for example have rolling resistance at the interface of the tire and the road. The small flat spot on the bottom of the tire is created by the rubber flexing. So to roll the tire has to climb that flat spot (drag) constantly regardless of speed. .... And I dont think a jeep can go fast enough to make a tire balloon.

You also mentioned the rotational inertia of the tire. That is stored energy and you get all of that back when you slow down. Yes it takes more energy to accelerate the more mass you have but it also carries you once you let off the pedal.

thanks! im working on breaking it down into tiny pieces to understand it. Its slowly making more sense.

 

[FloridaJT6MT]

 

[Gren71]

Day 2

Trip 2
23.1 MPG
-af 1 was present
-af 2 didn’t happen
-af 3 was present
- minor wind and 26d outside, not enough wind to rule out the day. The temperature has me wondering if its a contributing factor or not. Ex: maybe the lower air temp @ the intake changes the fuel use requirements in a negative way. If I remember (Cadbury egg brain thanks to the army) ill use the jscan app the see what the intake temp is.

 

[1996XJ]

Trip 2
23.1 MPG
-af 1 was present
-af 2 didn’t happen
-af 3 was present
- minor wind and 26d outside, not enough wind to rule out the day. The temperature has me wondering if its a contributing factor or not. Ex: maybe the lower air temp @ the intake changes the fuel use requirements in a negative way. If I remember (Cadbury egg brain thanks to the army) ill use the jscan app the see what the intake temp is.
[/QUOTE]

One more idiocracy line when jay goes to the doctor. " the chart says your shits phucked up"

 

[Gren71]

One more idiocracy line when jay goes to the doctor. " the chart says your shits phucked up"

Working in emergency medicine, I have to actively fight the urge to quote that scene on a daily basis.

 

[1996XJ]

Working in emergency medicine, I have to actively fight the urge to quote that scene on a daily basis.

lol!!! If i quoted that in full, i knew i would get booted. I promised you guys i would get banned once i got my mojave. So its coming soon. That doctor visit scene was the funniest. Best of luck to you friend on your career. We need guys like you with a sense of humor and a down to earth attitude helping people out.

 

[jeepin48]

I just noticed you had the wheel well wind deflectors also. All along I figured you were talking about the lower wind dam below the bumper. ....

When will you be making changes (removing the air dams)?

 

[Gren71]

I just noticed you had the wheel well wind deflectors also. All along I figured you were talking about the lower wind dam below the bumper. ....

When will you be making changes (removing the air dams)?

The experiment is to see if the addition of the (wheel well) air dams makes a notable difference in mpg. So my 20.5 over all average, and 22mpg trip average, was as you see my JT but without airdams.

so far, with only two days of data, they do seem to making a difference given anecdotal findings and the increase in mpg. But more data will tell the tale.

unfortunately I have inclement weather expected over the next couple days so some day’s data may be excluded. But ill still track since it will be interesting to see of there’s a difference even with weather.

as far as removing the lower air dam. I hadn’t really considering removing that. Im positive it would make a negative impact, just not sure how much.

 

[Gren71]

Day 3
Trip 1
23.6mpg
Mild wind, 29d ambiant temp.
-af 1 present
-af 2 present, traveled an additional 0.3 miles before shift
-af 3 present

 

[Gren71]

Day 4
Trip 1
23.6Mpg
-30d, no wind
-af 1 present
-af 2 didn’t occur
-af 3 present

 

[KWin]

So far looks like you gained a mile and a half per gallon!

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