What's the theory behind your equation bunger?

Miles per gallon is meaningful. it's a ratio that has an inherent explanation: it's the average number of miles you can go with each gallon of fuel.

Miles per hour is how many miles you are going on average each hour.

What does mpg/lb really indicate? It's because mpg is generally inversely proportional to weight. The lighter the car, the higher the mpg, so of course the number will get bigger if you divide a smaller weight into the higher mpg number.

The reason it doesn't make much sense to me is because I haven't seen a practical explanation. For example, if you take mpg/ton and use it as some kind of standard, are we saying that's how many mpg a car can get for each pound? Does that scale? If I take a 2000 lb car that gets 40 mpg, I get 40mpg/1 ton = 40. Then if that car's weight were increased to 4000 lb, would I get 80 mpg? No, of course not.

You can either compare your efficiency to a standard like EPA (such as it is), or compare two numbers that are normally proportional in comparison. In other words, multiply numbers that are inversely proportional, or divide numbers that are proportional. This makes for a comparative index that shows real gains in the world of vehicle utility.

Then there's power-to-weight. The higher the power and lower the weight, higher the number. It's meaningless except for raw acceleration numbers.

Please, continue to elaborate. I'd like to hear more.

I'm so confused now that I'll just follow the thread and see where it goes.:confused::confused:. I'm still trying to figure out why the weight needs to be in there to compare cars. If your car is heavy or powerfull won't the EPA number reflect the car abilities with low numbers? What ever is decided it needs to be simple enough for us hard heads to do.:)

weight * mpg
= weight * distance / energy

do you understand the significance now?

weight / distance / energy
doesnt make any sense.

yes its not a precise statistic and many other things can factor in, HOWEVER isnt the same true with the power/weight ratio? other factors being traction, suspension and gearing?

i dont like the points system, too complex and superfluous.

i still stand behind weight*mpg.

here is a quick notepad table of the people who have posted so far.
3880 * 45.0 / 1000 = 174.600 escape hybrid (Escape_Hybrid)
2070 * 66.8 / 1000 = 138.276 honda civic (basjoos)
2392 * 55.4 / 1000 = 132.517 (diamondlarry)
2200 * 56.5 / 1000 = 124.300 honda delsol (krousdb)
1800 * 59.3 / 1000 = 108.519 for the Blackfly (MetroMPG)
2950 * 34.4 / 1000 = 101.480 (zpiloto)
2500 * 39.8 / 1000 = 99.500 (Randy)
2965 * 29.9 / 1000 = 88.653 nissan altima (Compaq888)
2130 * 40.2 / 1000 = 85.626 honda civic (thisisntjared)
2000 * 40.0 / 1000 = 80.000 honda crx (SVOboy)
1807 * 43.0 / 1000 = 77.701 metro (95metro)
2350 * 32.2 / 1000 = 75.670 (kickflipjr)

maybe the number should be divided by 2000 so we have ton*mile/gallon

3880 * 45.0 / 2000 = 87.300 escape hybrid (Escape_Hybrid)
2070 * 66.8 / 1000 = 69.138 honda civic (basjoos)
2392 * 55.4 / 2000 = 66.254(diamondlarry)
2200 * 56.5 / 2000 = 62.150 honda delsol (krousdb)
1800 * 59.3 / 2000 = 54.260 for the Blackfly (MetroMPG)
2950 * 34.4 / 2000 = 50.740 (zpiloto)
2500 * 39.8 / 2000 = 49.250 (Randy)
2965 * 29.9 / 2000 = 44.327 nissan altima (Compaq888)
2130 * 40.2 / 2000 = 42.813 honda civic (thisisntjared)
2000 * 40.0 / 2000 = 40.000 honda crx (SVOboy)
1807 * 43.0 / 2000 = 38.851 metro (95metro)
2350 * 32.2 / 2000 = 37.835 (kickflipjr)

This is an interesting concept, and one that I think would help compare apples to oranges ( or a Ford Escape Hybrid to a Prius ).

Based on weight, I beat the socks off any other hybrid.

My FEH weighs 3880 pounds with a full tank of gas.
(I have a certified truck scale at work.) :D

My best segment over flat terrain was 75.5 MPG for 11.9 miles.
The round-trip home that night was 68.3 MPG for 20.2 miles.

So...75.5 / 3880 = 0.01945 MPG per pound. Does that make sense?
No... don't think so... having a heavier car makes the number smaller....
Gotta multiply, I think....

75.5 x 3880 = 292940 MPG Pounds.

I think MPG Pounds is the correct route to go. Agree?

Now take an Insight. *estimate, I've never owned one

*109 MPG x *1900 pounds = 207100 MPG Pounds.

Wooo hooo! Going by that, I can beat an Insight in my Ford SUV?

Does everyone agree this is a fair way to compare? Thanks.
-J

My FEH weighs 3880 pounds with a full tank of gas.
(I have a certified truck scale at work.) :D

My best segment over flat terrain was 75.5 MPG for 11.9 miles.
My second best was 68.3 MPG for 20.2 miles.
My tanks average about 45 MPG.

75.5 x 3880 /1000 = 292.240 ( best case )
45 x 3880 /1000 = 174.600 ( average )

-John
P.S. I think this is a pretty good quick and easy comparison. And yes, it does statistically make sense.
Now, if you want to throw in air drag, go ahead. That will boost my numbers, as this is a small SUV shaped like a brick!

That's 39.8 thankyouverymuch. :p

The reason this sort of number is interesting is when comparing very different vehicles. Like a semi... 70k+ lbs, but they get 6 or so mpg on the highway. That would easily trounce the best so far. Things like trains or ships burn insane amounts of fuel... unless you factor in weight, then they trounce anything on the road.

Note that the new CAFE standards are based on this sort of concept. It measures 'footprint'... the area of wheel base times wheel track, then reduces required MPG based on it. Critics say manufacturers will push bigger vehicles, but proponents say small vehicles kill and therefore shouldn't be pushed by CAFE. No, seriously, that's what they say... check out highwaysafety.org.

crap sorry man i fixed it.

regarding the CAFE standars, some people are just too busy pushing their own agenda to care about truth.

You never added me, nice man. 80 is my rating, 40 mpg. Figure out the rest!

YES! Exactly! This is a measure of efficiency! A train is very efficient on fuel! Which is what most people want to know... how efficient their car is.
This is a measure of "usefulness" also. An Insight or Geo uses fewer absolute gallons of gas than mine, but those cars are also less useful. ( in the sense of hauling goods, going on vacation, comfort, etc. )

thats a good point. thats part of why i think this statistic is so important. because bikes(motorcylces) murder even the nicest hybrids but they are so far from practical.

If we wanted to talk usefullness we would have to add usedness, because I doubt you haul 500 pounds of sheetrock every day on your FEH, just like I don't haul 2 engines every day in my CRX, :p

ah but you dont haul around 3 kids in a crx. the use of the usefulness is irrelevant. we are talking about the cars and the drivers driving habits, not necisarily the lifestyle of the driver.

Not every day, no, sometimes, yes. And it's darn handy picking up relatives from the airport, and lugging stuff home from Costco or Sam's Club!!!

I'm confused by your 2 engines comment, I presume referring to the Hybrid.
Since I do tote "2 engines" and the added weight, and still get 45 MPG, does that not mean my car is doing even better that previously thought?

For the record... motorcycles are the LEAST efficient out there, but you'll have a smaller gas bill each week!

-John

I mean that I can haul two engines physically in my car.

I think the use of usefullness is very important, because who gives a **** if I can haul 8 people if I'm the only person in the car at any given time. That doesn't make it more efficient, but it would if I carpooled with my coworkers.

this is incorrect logic i will fix it.
the advantage is that the other car can haul 8 if needed. you dont know if that escape carries a family of five every day and they shouldnt have to prove you wrong

The more I think about it the more I like it. MPG LbS is a great way to compare apples to oranges.

If I can get 50MPG in my civic sedan, which weighs 2200lbs, my score is smaller than a Ford F150 getting 35mpg. It's no question that smaller cars get better gas mileage, but can you take a mack truck and make it get above 20MPG?

[quote=Randy]That's 39.8 thankyouverymuch. :p

The reason this sort of number is interesting is when comparing very different vehicles. Like a semi... 70k+ lbs, but they get 6 or so mpg on the highway. That would easily trounce the best so far. Things like trains or ships burn insane amounts of fuel... unless you factor in weight, then they trounce anything on the road.

Ok now I'm starting to get it. :D
mines 3950 on the weight.

I understand that this is a measure of efficiency - though we now need to define what efficiency is and all that it includes. I did not realize that the 1000 number you used was energy. Was there a basis for choosing 1000 or was it just picked out of the air?

Out of the air numbers are what I don't like - sorry, it's just my personal nitpickyness. I like to have things defined and have a reason for being. If the number is just a number for the sake of showcasing then there is no reason to use it from a data standpoint.

Yes, mpg/lb makes no sense on its own, but neither does power to weight, horsepower, torque, or anything else on their own. They are stats and nothing but stats. mpg/lb is a wildly variable stat and that makes it worse, but it is still just a statistic...which I think is all MetroMPG was trying to do in the first place, but we've horribly hijacked his thread - sorry, Darin, for perpetrating some dead-horse flogging.

Overall I'm saying that if we are going to come up with a number to rate vehicles by then we have to reason through it, define terminology, and be able to prove it over and over again.

i cant believe you think weight, power to weight, torque, horsepower mean nothing on their own. yes they do. the represent a specific value that is useful. weight/mpg is not useful. it will never represent anything. weight*mpg does represent something, i broke it down for you. you need to get back to your highschool physics courses.1000 was out of thin air to make the number easier to read, however now i think it would be better if we did to to the ton. so the number would be 2000.

mpg is distance divided by energy. hense miles per gallon of gasoline. miles is distance. gasoline is the energy. thats where this comes from. i think we should definitely do it according to weight in tons.
we have a number to rate vehicles, its mpg. theres no need to go crazy with this. this isnt a scientific method or anything like that its just a number. that is all. its a number, just like power to weight, 0-60, its just a raw number. what needs to be proven? this is not that big of a deal guys. its just a creative way of thinking.

the ton mpg factors out weight, it is simply a tool for you to recognize weaknesses in your cars efficiency. if your mpg is above the epa but your ton mpg is low in respect to other peoples, then to improve your raw mpg it might help to focus on things unrelated to removing weight. likewise if you want better mpg and you are ranking very high on the ton mpg then weight reduction might help you more than you think.

understand that this number doesnt really help me at all and i dont care about how we a 'ranked' against each other. its not a scale of which car is better, nor is it a ranking system or anything like that. its a statistic. its just a number. it is a tool not a status symbol.
are you sure about that? that sounds more like the vehicles gross weight and not curb weight.

No problem at all. I'm just being intellectually lazy on this one and waiting for the dust to settle. :D

(And this was actually JanGeo's concept originally. I see he's also conspicuously absent in the debate.)

OOoo! That ^^^ was my 1000th post. I'm not sure if that's a good thing. :confused:

so i am alone in this....arg

im going to abstain from this thread for 24 hours then.

No, no - don't abstain yet - I'm probably going to have to apologize and concede defeat. I totally missed this little equals sign:

weight * mpg
= weight * distance / energy

Thus misconstruing what you were trying to get at once again. The little light's come on now and I get the formula at least...although the final number still leaves me baffled as to what you would call it.

Usability rating? How usable is a semi or train to the average driver though? :p I find my Aerostar useful for packing crap into, but as a daily driver? Damn wasteful, IMO. Which is why the number needs some definition if we're going to use it in the "garage".

As for my comments regarding hp, torque, etc. meaning nothing on their own, well...in a sense they don't.

Say I have ABC car that makes 800 hp. Okay, nice big, fat number, but it doesn't tell me jack about the car. Give me a few more stats in combination, torque, weight, 1/4 mile time, braking distance, etc and at least I can form a picture. Even 1/4 mile time doesn't mean much unless you compare it to another vehicle.

That's all I'm trying to say. In a very, very long, drawn out, round-about way...:D :o

Quote:
Originally Posted by zpiloto
mines 3950 on the weight.

are you sure about that? that sounds more like the vehicles gross weight and not curb weight.

You're right that is the GVWR.:o Sorry. Now to try and find the curb weight.

Okay, last "figuring it out" post for me in this thread. I finally have a suggestion for what to call this formula at least.

First, we alter it moderately just so we know what we are doing:

Vehicle weight / 2000 lb (1 ton) * mpg (use previous 3 fills for now)

So, my Metro is:

1808 lb / 2000 lb = 0.904 tons

0.904 * 43.041 mpg = 38.909

38.909...what??? This is what I was struggling with...what the hell do we call it...and I think I finally hit it: weighed miles per gallon (or would it be weighted miles per gallon?)

So, my Metro is 38.909 wmpg

For some reason I have this feeling that part of getting good FE is making possible sacrifices to buy lighter or slower cars, and that that sacrafice will just be eliminated with a statistic like this.

I think what this really is trying to get at is driver skill, which I think is covered by % over epa, yeah?

back
 

Sorry guys had a bit of holiday work overload - everybody wants me Saturday for something - I need a vacation! I was up at 6:00am and out the door at 6:10am and back at 11:26pm talk about a long Friday!

% over EPA is the main game, yes.

But I like the idea of trying out another data point for comparison, since I learned that my car's EPA is much more optimistic than other vehicles (so, harder to beat).

I'm not stressing over it, just curious how this plays out. It may reveal something interesting.

precisely. however this is not a weighted mpg at all. it is just another number. the efficiency-weight product.

ben has a point, however this is not a matter of driver skill. this statistic is a cars fuel economy with the factor of weight removed. its not that big of a deal and the type of driving the car does will greatly effect this statistic (city vs. highway)

i still think that the % over epa is the best standard for measuring your progress, however the efficiency-weight product can help, as i have mentioned in another post on this thread.

the abstinance really helped me.:

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.

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

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). ;-)

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. (https://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??

bump. ;-) I like this thread. :D

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!

CarloSW2

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

looks like the metro experience is 1766 + 185 = 1951lbs * 70.15 mpg / 1 = 136863 lb miles

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)

:D ooopppsss...guess that is late night typing for ya!

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?