What's your fuel economy to weight ratio? - Page 8 - Fuelly Forums

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Old 05-27-2006, 12:26 PM   #71
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The only person/car you can compete fairly against is yourself. No two people have the same driving conditions. If we wanted to have a meet where we do some sort of road rally then the conditions would be the same and not necessarily favorable to a particular setup. But that is not really in the spirit of this site which is to help each other get the best MPG we can out of our cars. My personal opinion is that the percent over the EPA estimate is about the best you can do if you want to compare completely different vehicles.
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Old 05-28-2006, 08:26 AM   #72
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Using Metro's original formula and using the average MPG for my car since I starting installing the aero mods:

2070 lbs (OEM 2090 lbs, minus front passenger seat)
66.8 mpg

2070 (66.8)/1000 = 138.276
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Old 10-29-2007, 07:07 PM   #73
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Thumbs up What became of this?

I see this is a dead thread but I'm a newbie and catching up on everything here as I find time. I found this thread particularly interesting. I would personally love to see the field "avg total vehicle weight during trip" added to the gas logs, and have "lb*mpg/1000" displayed in addition to just "mpg". lb*mpg is useful data, not just for comparing one vehicle to another, but for comparing one vehicle to itself as you add/remove weight, be it passengers or cargo.

Looking at similar vehicles shows you what is realistically possible with your own. For example, suppose someone here has the same vehicle as mine, but they've removed the passenger and rear seats and spare tire, and they never drive with passengers. I wouldn't expect to be able to achieve the same mpg as them if I always drive with two passengers, a dog, and sports gear. However, I would expect to be able to achieve the same or better lb*mpg (assuming I drove similarly and made similar modifications other than weight reduction).

While it is a useful stat to know, lb*mpg is not a stat you want to optimize like mpg is. To illustrate the point, the fastest way to increase the lb*mpg of your vehicle would be to put a load of bricks in it. Your lb will increase more than your mpg will decrease (because your drag stays the same) so your lb*mpg will increase. One might argue that this is a reason to use curb weight instead of total weight, but then you are just favoring the person who buys an over-designed vehicle with the bricks built-in and you don't get to look at the variation of lb*mpg on a single vehicle as you add/remove weight.

Anyway, I'm not sure what became of this, but is there a possibility of letting people post their "avg total vehicle weight during trip" in the gas logs, and displaying "lb*mpg/1000" or "ton*mpg" in addition to "mpg". Clearly it would be up to each individual to use this field or not, but judging by the posts I've seen, I think a great many people would use it. Also, I suppose judging by the confusion around it, it would need to be written up somewhere so people could understand how to use it.

Would also be great to see fields for Cd*A and Crr but those are more difficult to measure.

PS. If you want a new stat to compete on for the top 10, make it occupants*mpg. Then the incentive is both to carpool and to diet (or drive your kids lots of places). ;-)
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Old 10-29-2007, 09:12 PM   #74
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Well...let another newbie jump in here...seems to me that something was missed.

I see a lb*mpg / whatever being thrown around...but why not just keep it simpler and go for something more like a torque/work rating?

---> lbs * miles driven / gallons used? This will let you know how much WORK was done for the gallon of gasoline that was burned.

This is a similar measure that freight trains use to calculate fuel use. (http://en.wikipedia.org/wiki/Fuel_ef...rtation#Trains)
"Freight: the AAR claims an energy efficiency of over 400 short ton-miles per gallon of diesel fuel in 2004 (0.588 L/100 km per tonne or 235 J/(km·kg))"

So, in my case, my car (MB 190e) would yield approximately:

2900 * 28 / 1 gallon = 81200 lb miles

and if I put 4 fullsized adults (200lbs each) it would be:

3700 * 24 / 1 gallon = 88800 lb miles


My wife's car (2003 Taurus Wagon) would be:

3500 * 22 / 1 gallon = 77000

with 5 people (@ 200lbs each):

4500 * 20 / 1 gallon = 90000

Metro's numbers would be:

1830 * 59.3 / 1 gallon = 108519 lb miles

An unloaded average F-150 regular cab would yield:

4800 * 18 / 1 gallon = 86400 lb miles

but loaded with it's 1000lb payload

5800 * 16 / 1 gallon = 92800 lb miles


and a loaded road bus (greyhound type):

32000 * 7 / 1 gallon = 224000 lb miles

a fully loaded semi:

80000 * 5 / 1 gallon = 400000 lb miles

a road tractor bobtailing:

14000 * 12 / 1 gallon = 168000 lb miles

And the train from the above link would get:

1 gallon = 800000 lb miles


Whatcha think??
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Old 10-30-2007, 07:31 AM   #75
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bump. ;-) I like this thread.
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Old 10-30-2007, 09:01 AM   #76
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rvanengen -

Here's my SW2 :

(2456 + 140[me] + 70[various crap in my car] * 41 / 1 Gallon = 109306 lb miles

Sooooooo, I'm a Geo Metro. Do I have to change my badges?!?!?!?

Or ... 13.7% of a train!

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Old 10-30-2007, 09:29 AM   #77
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With at least one extra 50 pound 7 year old body averaged in, I just creep over the 100K mark. If this vehicle were just used on out of town highway trips where mileage gets to around 27 and the load is 500 pounds higher, it would get to the 136K mark.

(4289 + 215 + 50) x 22.18 = 101,001
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Old 10-30-2007, 09:56 AM   #78
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looks like the metro experience is 1766 + 185 = 1951lbs * 70.15 mpg / 1 = 136863 lb miles
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Old 10-30-2007, 09:57 AM   #79
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I suppose, my numbers were a little low since the FE amount was with 2 adults and 1 child + accessories...so, I should adjust my numbers to be:


So, in my case, my car (1991 MB 190e) would yield approximately:

(2900 + 260 (me) + 50 (junk)) = 3210 lbs

3210 * 28 / 1 gallon = 89880lb miles (not 81200)


My wife's car (2003 Taurus Wagon) would be:

3500 + 440 (us) + 75 (junk) = 4015

3500 * 22 / 1 gallon = 88330 lb miles (not 77000)

ooopppsss...guess that is late night typing for ya!
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Old 10-30-2007, 10:01 AM   #80
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Quote:
Originally Posted by jwxr7 View Post
looks like the metro experience is 1766 + 185 = 1951lbs * 70.15 mpg / 1 = 136863 lb miles
Cool!! Just a *tad* bit higher than either of our cars!!

Now...if there was a good objective measure for "utility"...seems like we have a good measure for efficiency!

Wonder where everyone went on the original thread?
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