“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Sunday, April 06, 2014

Elio Motors proposes an 84 m.p.g. "car"

The Elio Motors three wheeler is a design by Paul Elio that is expected to achieve a highway fuel economy of 84 m.p.g. (and a city fuel economy of 49 m.p.g.). The vehicle is expected to be on sale in 2015 at a price of $6,800. The price includes air conditioning, power windows, power door lock, AM/FM stereo, "and more." It's expected to have a 5 Star Crash Test Rating (the Elio has a reinforced roll cage, antilock brake system, stability control, airbags, and is made from carbon fiber composite).

It's not actually a "car" in the sense that we commonly think of them, it's a three wheeled vehicle. It seats two in a tandem configuration. For most states, that means that the Elio is regulated as a motorcycle (and in some states, a helmet will be required as things stand now). Pre-orders for the vehicle (with deposit) are said to be at 12,000, and Paul Elio believes that he can sell 250,000 Elios per year.

I can think of several applications where such a vehicle could excel. For example, I drive to work alone nearly every day and, in fact, well over 90% of the miles I drive my Lexus CT 200h are solo. I ran a quick check and the Elio would reduce my 400 gallons per year to 322 gallons for a savings of something like $312. Were I buying a new car, such a choice might be attractive at the $6,800 price point.

The Elio would likely also be a good candidate for a second vehicle for grocery shopping and other errands in a soccer mom family with the requisite minivan or SUV.

What about taxis? Here it's not so clear. The only door is to the driver's left and the rear seat is, charitably speaking, not optimized for the passenger experience (not to say claustrophobia inducing). And much taxi driving is in cities, where the Elio doesn't do any better than a Prius hybrid (and lots of my taxi rides recently have been in Priuses).

Fleet vehicles? Possibly, it certainly depends on the fleet and its intended use. What about for rental agencies? Here I'm also not so sure. I don't put a lot of miles on my rental cars when I'm out of town, I'm not so sure that I'm atypical. Thus, the fuel economy might not be particularly attractive. On the other hand, if the rental agency were to reduce the rental charge in proportion to the acquisition price of the Elio, we might have a deal.

Elio has a variety of fascinating financing options, the best article on those that I've seen is at this article in "the truth about cars" web site. The basis is that you get a credit card whose balance is the remainder of what you owe on the car after your deposit/trade in credit. You make payments on the card and when you purchase gas, you're billed for three times the gasoline cost. The difference between that price and the actual cost is used to pay down the car loan balance. The theory is that you're getting three times the fuel economy so you get the new Elio without paying anything beyond what you're used to paying for fuel for your (presumably) old, inefficient vehicle.

Now, one could say that the Volt, the Leaf, etc. do better than the Elio with respect to fuel cost (be they gallons or kilowatt hours) and one would be right. And those are four seat, four wheel vehicles. But, for the price of a Volt or a Leaf, one could buy an Elio and have some $30K left over. And it would certainly seem to be strong competition for the two seat Smart Car.

What about the mileage claim? The vehicle weighs about 1,000 pounds and sports a 70 horsepower, three cylinder engine. It doesn't look to be an aerodynamically smooth vehicle, but aerodynamics can be extremely deceiving. I can find no figures on drag coefficient or frontal area. But such trifles haven't stopped me before, so I'm going to plug and chug to see what results.

I'll assume a weight with driver of 1,170 pounds, a Cd of 0.32 (purely a guess, and one that I think favors the vehicle), tire rolling resistance coefficient of 0.0085 (assuming that Elio will go with low rolling resistance tires), an efficiency for the internal combustion engine of 30%, a frontal area of 2.3 m2 and a highway speed of 60 m.p.h. Running this in my little Mathematica model of vehicle fuel economy yields an estimate of 67 m.p.g., 17 m.p.g. below Elio's claim. I think I've been generous with respect to engine efficiency, so the likely areas where I've "cheated" the Elio would be drag coefficient and frontal area. Frankly, I think I've been pretty generous here as well, so I'll be very surprised if the typical driver* achieves 84 m.p.g.

Finally, I have to apologize for the lack of posts in the last nearly three months. As my karate instructor made us say when he asked us why we made some mistake in form or execution, "NO EXCUSE SIR!"

*Driving at 55 m.p.h. as I do yields an estimate of 78 m.p.g.


Anonymous said...

It will be great if Elio Motors succeeds at this. But I cannot understate how hard it will be to get this on the market for $6800.

Creating a motorcycle is much easier than a car, but still is much harder than it seems.

Corbin, Aptera et al have tried and then run out of money because the cost of developing a product is so huge.

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Unknown said...

I too hope this comes to market and eventually a plugin hybrid or extended range EV version comes out!
It looks like it'll be a great chassis but the engine is holding back efficiency.
This would help it compete with the Lit Motors C-1.

What formula did you use for calculating MPG?

Rob Ryan said...


I don't know if I can use latex in comments so:

I use 0.5*cd*\[Rho]*a*v^2 + rr*g*m for the resisting force with cd: coefficient of drag; rho: air density; a: frontal area; v: speed; rr: tire coefficient of rolling resistance; g: acceleration of gravity; m: vehicle mass. This gives external resistance (a force). Then that, multiplied by speed, gives power. Power is energy per second and I calculate assuming that gasoline has about 125 megajoules of energy per gallon. I assume 25% efficiency to the driving wheels.

It's worked out very well for the vehicles for which I have sufficient data to verify. In the case of the Elio, many things are estimates with little supporting data (drag coefficient in particular) so we shall see.

You must make sure that you use consistent units. If you check all of that from base dimensions, you'll see that you do, in fact, get joules/second, or watts when you calculate the power.