Where Did 84 Mpg Come From?

[pistonboy]

Rewinding to the beginning of this (old) thread where (paraphrasing) the OP was questioning that the goal of 84mpg seemed arbitrary so why waste time pursuing an arbitrary mpg target why not be happy with a slightly lower number why waste time and money "tweaking" to get to the 84mpg goal.

I'd had a somewhat similar thought but with an almost opposite conclusion - I was remembering that the automotive X prize set the goal of a mass producible car that did *100 mpg*.

You could argue that "100" was a likewise arbitrary number - but I don't think it's *psychologically* arbitrary - I think "100" is kind of a easy to remember number which for marketing purposes would be more impressive (if it were possible?). i.e. It's a little easier for me to imagine somebody excitedly saying "wow did you see that three wheeled elio car did you know it gets *100* miles per gallon!!" than "wow did you see that three wheeled elio car did you know it gets 84 miles per gallon".

(or maybe I'm wrong - as I write that I guess 84 does sound impressive too)

My real comment/question in writing the above is for you mechanically savvy people on this forum: Could there have been any way to achieve 100mpg with the Elio?

I guess I imagine generally (from freshmen physics!) the ways you might achieve 100mpg would be: a. reduce weight, b. improve aerodynamics, c. reduce friction? (within the vehicle and/or "rolling resistance" with the road?), d. improve the efficiency of the engine... any others?

And final thought - I know so little about engines but I'd noted this three wheeled vehicle somewhat like the elio that did enter the automotive x-prize claimed to use a "fuel vapor" engine - could something similar help raise the mpg of the elio to 100+ mpg I wonder?

http://www.ridelust.com/fuel-vapor-ale-gets-92mpg-car-with-a-5-second-zero-to-sixty/

You said: "My real comment/question in writing the above is for you mechanically savvy people on this forum: Could there have been any way to achieve 100mpg with the Elio? "

The answer is yes. It is possible to dramatically increase the mpg for any vehicle. The problem is, we would not want to buy it.

My professor of mechanical engineering at University of Illinois said approximately 12 horsepower is needed to sustain a vehicle at 55 mpg. This is what it takes to overcome rolling resistance of the tires and air resistance at that speed. (This is for traditional vehicles of the 1970s) Find an engine that when operating at full throttle (which is most efficient point for engine) produces 12 horsepower. Put this engine into a car and the mpg will be tremendously higher. The problem is, acceleration time from 0 to 55 would be over an hour and no one would want the vehicle.

 

[Ekh]

Elio is really ambitious in attempting to reach 84 miles per gallon at highway speeds, as opposed to 55 miles an hour. The reason this is so ambitious is that the force resisting the Elio's forward progress increases as the square of the velocity.

That's why Paul Elio used to say that in the city it's the weight that counts and on the highway it's the slippery shape of the car that matters more.

The design of the Elio engine is slanted towards higher torque for exactly this reason. The Dual step cam and the long stroke relative to other engines and especially relative to motorcycle engines, is intended to keep the RPMs down while delivering power at 65 miles an hour. You give up a little on acceleration, and when you're accelerating you're burning relatively more gasoline, but at Highway Cruise you get it back in reduced RPMs, which means lower fuel burn.

This is a balancing act. There is no one solution that solves the problem. So Paul is continually searching 4 small ways to reduce the body weight, which it crept up there pretty alarmingly, as well as to keep the car as aerodynamically slippery as possible.

But he also has to produce a car which has enough features to sell well, which is comfortable, and which is still affordable. And safe. Making the car safe usually involves making it heavier and more expensive. See what a hard act this is to do?

Frankly, if the Elio delivers 80 miles a gallon down the highway and comes anywhere near its price point, Paul will deserve a Halo and a seat in the automotive Hall of Fame. This is incredibly difficult engineering challenge. You have to respect him for bringing Roush Engineering when Elio had reached a stuck point, and nobody, but nobody, can get other people involved in his passion then Paul Elio. I've said it before and I will say it again that he must have read Tom Sawyer at a very impressionable age.

What's got to be frustrating him and will be frustrating us is the difficulty of explaining to people just why 84 miles per gallon is so incredibly difficult to do, not for itself that's --it's not too hard to get there as somebody just pointed out, but to get there while meeting all the other goals-- now that is a challenge.

If the car winds up at 80 mpg, many will be quick to see it as a failure. Yet in truth it's a remarkable success, in a marketable car. But explaining that to the Great Unwashed is going to be a marketing problem for sure. IMO, Elio needs to nail this car down as soon as possible, and then publicize what it DOES do, as opposed to what it's TARGETED to do. And they need to do this soon, because they have to provide tested fuel economy figures to the DOE for the monster loan...

 

[Ekh]

Man EZ, you got it made in a lot of ways. I would not mind at all to be in your shoes. A tropical island and my sailboard and maybe a cold one after a great session on the water as the sun sets.....
But, then there's the wife and kids and life gets MUCH more complicated. All the priorities shift, and the next thing you know, the warm sand is a memory, the sailboard has been in the garage for 5 years covered in dust, and I'm looking over the inevitable abyss of another northern Michigan winter.
Here in the north, solar power is inefficient, and electric cars doubly so. Batteries don't work so well in the cold, running a heater on batteries would drain them in nothing flat, and the distances to ANYTHING are a huge problem. An ICE vehicle can go short OR long distances, instead of only short. And for the long distances fuel efficiency reigns supreme. I hate putting half my discresionary income into the gas tank, and I also hate having the carbon footprint of burning a small lake of gas per year just getting to work and back.
It would be an interesting project to get hold of an Elio and retro it into an EV as a proof of concept vehicle. Then if the results are good, maybe an EV division of Elio, or a small custom company could be set up to make Elio-EV from rolling chasis purchased from Elio. Just a thought, and I'm sure someone out there could do it. Just not someone with my limited resources.
Enjoy a little warmth for us poor s.o.b.'s up north. I'll be happy to build a snowman for you. :-)

Very well written post.

 

[Ekh]

Very well written post.

Where did 84 miles to gallon come from? I think Paul Elio got out his pocket calculator, did some fairly basic computations, and figured out it was possible to do it. Being the stubborn son-of-a-gun that he is suddenly found himself with a lifelong goal.

 

[Ty]

The average sedan gets 28mpg... and costs $20,400... 3 times 28mpg is 84mpg, 1/3 of $20,400 is $6,800...

 

[NSTG8R]

The average sedan gets 28mpg... and costs $20,400... 3 times 28mpg is 84mpg, 1/3 of $20,400 is $6,800...

Not sure if it follows the theme, but it weighs about 1/3 as much at the 1200 lbs they were shooting for. And I'll be able to carry 1/3 as many passengers as my Subaru can.

 

[AriLea]

Addressing the issue of 100 mpg has some good responses, but I think I could add a bit or two.

I used to work on high-mileage research vehicles, the Western Washington University Viking cars 4,5 and 6 from the early 1980's. Just a couple years ago WWU entered the Automotive Xprize based on meeting the 100MPG threshold. Viking cars are sociable seating 4 wheel sports cars. Comparable to a Miata, but better for mileage. The people who built the Avion which also competed in the AXP, were my classmates who entered their own car built in the 80's.

The basic premise for Viking car mileage is very similar to the Elio, small frontal area, small weight, good aerodynamics, correct choice of power train. This comes at the tradeoffs of passenger space, comfort, cargo capacity and also to some degree costs. These attributes could be summed up as motivators to buy the vehicle, translation? Count of sales are directly affected.

So basically the answer is yes, you can get 100mpg, but the car must not tradeoff too much if you want the benefit of mass sales giving lower costs. Elio motors feels they took it to the limit. In production year two maybe they will feel they can do more tradeoffs. So, yes more is possible.

My car logo to your left represents a car design, probably just over the limit. I estimate it as a 120mpg autocycle, but would cost double what an Elio does using Elio production. But given my tradeoffs I wouldn't get Elio sales at that level, so the tech I would be forced to use would cost triple or more what an Elio costs to produce.

And yes, I could trade more off, and get better mileage. Where exactly should that stop?

 

[Ekh]

Addressing the issue of 100 mpg has some good responses, but I think I could add a bit or two.

I used to work on high-mileage research vehicles, the Western Washington University Viking cars 4,5 and 6 from the early 1980's. Just a couple years ago WWU entered the Automotive Xprize based on meeting the 100MPG threshold. Viking cars are sociable seating 4 wheel sports cars. Comparable to a Miata, but better for mileage. The people who built the Avion which also competed in the AXP, were my classmates who entered their own car built in the 80's.

The basic premise for Viking car mileage is very similar to the Elio, small frontal area, small weight, good aerodynamics, correct choice of power train. This comes at the tradeoffs of passenger space, comfort, cargo capacity and also to some degree costs. These attributes could be summed up as motivators to buy the vehicle, translation? Count of sales are directly affected.

So basically the answer is yes, you can get 100mpg, but the car must not tradeoff too much if you want the benefit of mass sales giving lower costs. Elio motors feels they took it to the limit. In production year two maybe they will feel they can do more tradeoffs. So, yes more is possible.

My car logo to your left represents a car design, probably just over the limit. I estimate it as a 120mpg autocycle, but would cost double what an Elio does using Elio production. But given my tradeoffs I wouldn't get Elio sales at that level, so the tech I would be forced to use would cost triple or more what an Elio costs to produce.

And yes, I could trade more off, and get better mileage. Where exactly should that stop?

Excellent post

 

[AriLea]

PS, the Avion.

The faces people made are charming! The first Elio's out will get that kind of attention, plus some.

Years later! Same guy!

 

[AriLea]

Viking 45...