What Speed Do We Have To Travel To Get 84mpg?

[Adamant]

I hope this is not a case where in order to get 84mpg we have to do 55mph down the highway with no A/C on. Do you think it's possible we could travel at the speed limit (70mph) with A/C on high, and still get 84mpg?

Also, another thing I was wondering about... on my way to Las Vegas last year, I noticed there are a LOT of stretches of road (like 10 mile straight aways) where there's not another car around for miles and you're all alone, with perfect visibility, etc. So my question is, if I'm traveling down these types of roads with no one else around and I want to go 90-95mph in the Elio, what type of gas mileage could I expect then? Obviously I wouldn't expect 84mpg, but do you still think the vehicle is capable of getting more than, say, 40mpg at this speed on the open highway?

 

[ks6c]

The EPA mileage estimates are determined using a specific driving protocol, and you might find this article interesting: http://www.caranddriver.com/feature...y-mpg-estimates-measuring-fuel-economy-page-2

Specifically:
"In 1972, when regular gas was 35 cents a gallon, test cycles were invented by the newly created EPA to measure exhaust emissions. The first test cycle, which sought to mimic rush-hour traffic in downtown Los Angeles with an average speed of 21 mph, is called the FTP, or city cycle, and is still in use today. This dyno test is 11 miles long, takes just over 31 minutes to complete, involves 23 stops, reaches a top speed of 56 mph, and has maximum acceleration equivalent to a lazy, 18-second 0-to-60-mph run. A second cycle to measure highway driving was added in the late 1970s as part of the introduction of corporate average fuel-economy (CAFE) regulations. This 10.3-mile cycle with an average speed of a paltry 48 mph and acceleration no more severe than in the city test, may have been somewhat realistic in the days of the national 55-mph speed limit but doesn’t come close to approximating the manic highway behavior of today’s drivers. As a result, and even though the test figures were adjusted downward starting in the early 1980s in an attempt to produce more realistic sticker values (by 10 percent for the city test and 22 percent for the highway), the EPA numbers gave drivers too optimistic an expectation of fuel economy for decades."

IOW, Elios' 84mpg estimate is arrived at using (computer modeling) EPA's testing protocol which, by and large, won't bear any resemblance to your driving habits. So, to answer your first question about A/C, 70 mph and 84mpg, I think the official answer would be "no way in hell."

 

[Ekh]

I hope this is not a case where in order to get 84mpg we have to do 55mph down the highway with no A/C on. Do you think it's possible we could travel at the speed limit (70mph) with A/C on high, and still get 84mpg?

Also, another thing I was wondering about... on my way to Las Vegas last year, I noticed there are a LOT of stretches of road (like 10 mile straight aways) where there's not another car around for miles and you're all alone, with perfect visibility, etc. So my question is, if I'm traveling down these types of roads with no one else around and I want to go 90-95mph in the Elio, what type of gas mileage could I expect then? Obviously I wouldn't expect 84mpg, but do you still think the vehicle is capable of getting more than, say, 40mpg at this speed on the open highway?

Jerome Vasallo told me that the Elio was being designed to relier 84 mpg at 65 mph. "We wanted real world economy," he said. Hence the very torquey engine, to deliver the highway speed at low rpm.

 

[skygazer6033]

I believe that to be correct Ekh. If I recall a discussion from many months ago EM stated their mpg specs were to be based on more realistic driving conditions. IIRC standard day conditions, straight and level road with 0 wind, A/C on, 170 lb. driver, no passenger, full fuel and oil. 84 mpg. Don't know if that spec would actually be driven or simulated on a dyno. So in order to really stir the pot I believe it would take about 96 mpg EPA spec to match the EM 84 mpg spec.

 

[ks6c]

Jerome Vasallo told me that the Elio was being designed to relier 84 mpg at 65 mph. "We wanted real world economy," he said. Hence the very torquey engine, to deliver the highway speed at low rpm.

I believe that to be correct Ekh. If I recall a discussion from many months ago EM stated their mpg specs were to be based on more realistic driving conditions. IIRC standard day conditions, straight and level road with 0 wind, A/C on, 170 lb. driver, no passenger, full fuel and oil. 84 mpg. Don't know if that spec would actually be driven or simulated on a dyno. So in order to really stir the pot I believe it would take about 96 mpg EPA spec to match the EM 84 mpg spec.

Thank you both for bringing Jerome's comments back to the fore - quite frankly, I had forgotten about them.

That said, do we know what claims EM has made in the technical specifications that would have been part of their ATVM loan application? I would have to imagine they would have been stated in government-approved EPA-speak.

 

[Lil4X]

Use of the AC, assuming it will not be electrically driven but belt driven from the engine, is going to cut deeply into fuel economy. My '95 Civic would do 36 mpg reliably on a three hour Interstate run without the AC, but only 32 in warm weather with it running . . . and that was with 125 hp on tap. My '72 Opel was similar, but with only 105 hp available you definitely knew when the AC came on. When you have only 50 horsepower available, the 8-10 hp required to run the compressor becomes really significant. You should expect that when your compressor cycles on it's going to feel like you've thrown out an anchor.

Most AC systems use either a vacuum motor or a signal from the Engine Control Module to disconnect the compressor clutch at WOT, restoring those extra horsepower to get out of trouble when in panic mode. As soon as you lift you'll get that toe-stubbing sensation as the compressor kicks back in. That's why I'm all for an electrically-driven compressor, particularly with a tiny engine. It's more expensive, but well worth in when drivability is a consideration.

 

[Coss]

I've heard this tossed around for a long time; the current word is, with the aerodynamics of the new vehicles keeping the windows closed at highway speeds and the A/C on is better. Open windows cause drag, and A/C puts drag on the motor but the mileage loss is greater with the windows open.
One thing that has changed in cars is that A/C compressors are now engaged every time you have your motor running; they did this because there were too many cases of people never using their A/C for long stretches then one day turning it on and the compressor having never been used would lock up and tear the belts apart; I think they started doing this in 2000 or 2001. So your A/C compressor is always engaged but it has a bypass internally for the cooling. You'll see on newer cars on a really humid day that the A/C will pull moisture out of the system even if you don't have the A/C on; you'll see the tell tale water puddle under the car when you park the car.

So with this taken into consideration, it is better to have windows up and A/C on to get most efficient operation. Ideally it would be windows up and A/C off for best mileage; but I don't know many people with cool suits for driving.

 

[skygazer6033]

Actually an engine driven variable displacement compressor like a Harrison V5 is far more efficient than an all electric system. One way or the other the power to operate the A/C has to come that tiny little engine. Electric A/C would need a bigger alternator which would have to work harder when the A/C engages. Now you have efficiency loses of converting mechanical energy to electrical energy and back again within the A/C unit. With only 55 hp to start with EM can't afford the energy loss.

 

[Ekh]

I believe that to be correct Ekh. If I recall a discussion from many months ago EM stated their mpg specs were to be based on more realistic driving conditions. IIRC standard day conditions, straight and level road with 0 wind, A/C on, 170 lb. driver, no passenger, full fuel and oil. 84 mpg. Don't know if that spec would actually be driven or simulated on a dyno. So in order to really stir the pot I believe it would take about 96 mpg EPA spec to match the EM 84 mpg spec.

Well, since I weigh 170, all i need is a level road on a hot, calm day ...

 

[skygazer6033]

Unfortunately many of us will need a straight level road, no wind AND loose a few pounds to meet the prerequisite spec for the 84 mpg.