• Sep 6th 2008 at 8:06PM
  • 37
The Chevrolet Volt raises a lot of questions. From its public unveiling in January 2007 people wondered, is it a hybrid or an electric car? Right from day 1 in December 2006 before the auto show, GM officials have called it a range extended electric car. They use the electric car terminology because, unlike what we think of as hybrids today, only an electric motor drives the Volt. The engine, a normally aspirated 1.4L (not turbocharged as Motor Trend indicates) just drives a generator (not a two mode hybrid unit as MT says) instead of the wheels. However, the presence of the range extender causes the EPA to consider it a hybrid and they expect it to have almost a full charge at the end of the test cycle. The design intent is that the battery would be run down after having run more than its 40 mile electric range during the test. As designed, the engine would only run 15 percent of the time during the current EPA cycle and would yield over 100 mpg. But, using the EPA's methodology and having the engine keep the battery near full charge - which completely defeats the purpose of a plug-in vehicle with a 40 mile electric range - the Volt would only get about 48 mpg. While not a bad number, it's no where near reflective of what the Volt could achieve in the real world for most drivers. Clearly the EPA needs to work with manufacturers to change the testing methodology and come up with something that more closely approximates real world conditions for plug-in vehicles. Insisting on something else would force automakers to calibrate plug-ins to meet those requirements at the expense of real world efficiency, helping no one.


[Source: Motor Trend]


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  • 37 Comments
      • 7 Years Ago
      What I am interested in seeing is how the EPA will measure Electric-only range. The Volt Extended-Range Electric Vehicle (E-REV) is purported to drive and initial x distance (40 miles). No matter at what speed or at what acceleration level, the engine will not come on to help drive the car. The E-REV is supposed to make it unlikely that a driver will have to burn gas at all, even on the freeway. So its straightforward that will the Volt get an x mile (x ~= 40) EV range label.

      On the other hand, PHEVs will have the engine coming on and off a lot, based on speed and acceleration, since they can't run electric only above a certain power level and a certain speed level. If I drive a 1/4 mile from my garage to the freeway on-ramp, a PHEV engine will fire-up, even when the battery is full. What label do you give this car? 1/4 mile, Some cycle-averaged number, or simply zero miles, since there is really no way to guarantee an EV range.

      So the mpg label is not the only tricky part. How will the EPA address the fundamental difference in EV range these cars have?
      • 7 Years Ago
      But to call the Volt a 48mpg car is ludicrous! Most people won't use more than 5 or 6 gallons of gas a month at 1200 miles of driving. Almost all of my driving is done at the rate of about 20-30 miles per day. I won't use any gasoline most days. About once a month I go on a road trip and drive 200 miles. Then I will use 3 or 4 gallons, but the range extender will seldom be used otherwise. And that is how most people drive. We drive 12,000 miles a year, maybe 15,000 miles at most. And 15k miles a year is 41 miles a day. When you take the monthly road trip out of that the Volt doesn't use any gas for weeks at a time.
      We need to be independent of foreign oil, and having the EPA discouraging EREV tech is helping our enemies in Venezuela, Iran, Russia and Saudi Arabia. Do this logically, but don't let the bureaucrats damage our conversion to electric cars.
        • 7 Years Ago
        All of that is true, ziv, but the fact is that the EPA needs to be objective in testing vehicle MPG. All those things you said are things that dealerships can and should tell consumers to sell them the car, but the EPA should just give the hard data and nothing else. There's got to be a number, and when the battery is drained, the MPG is 48, apparently. That's what people will understand, so that's what the EPA should do. Let the dealer explain the advantages of having an all-electric range; it's not the EPA's job to do so.
      • 7 Years Ago
      I'm waiting for the McVolt, which will do all things. Meanwhile diesel-hybrid or CNG is fine.
      • 6 Years Ago
      The official, correct efficiency metric that EPA uses is:

      number of kilowatt hours per 100 miles (# kWh/100 miles).

      The lower the number, the more efficient the vehicle.

      The Volt is all electric drive, with a range extender. Mpg is a meaningless, obsolete metric.

      For example and for comparison, the 2009 Tesla Roadster is EPA certified at 28 kWh/ 100 miles and my daily driver street legal (kitted) registered lithium power pack all electric vehicle gets 2 kWh / 100 miles, 14 times more efficient than a Tesla Roadster, and cost less than $8,000.

      Pure gassers can have their old fuel economy metric (mpg) converted to the new correct EPA metric (kWh / 100 miles) quite easily, using the energy content in an average gallon of gasoline (don't forget that all retail gas includes 10% ethanol now, which contains less energy).
      • 7 Years Ago
      1. Completely charge vehicle (plugged)
      2. Run EPA test until tank is (nearly) empty
      3. Record total mileage
      4. Fill tank, record gallons used
      5. Divide total mileage by gallons used

      The result is the vehicle's MPG.

      The higher number of miles traveled will mitigate, but not eliminate, the mileage advantage of starting with a completely charged car. This advantage should not be eliminated entirely, since it is a unique and differentiating trait of the Volt itself.

      Running a single 46-mile course is ridiculously minimal. Full-to-empty testing would develop a unified standard based upon a concept we can all understand, a single full tank of gas.
        • 7 Years Ago
        I suppose you could do a run to empty test, if you weren't bright enough to figure out that you can do a much shorter test to fill in the gaps using some grade school math.

        You run a range test until the battery is exhausted (~40 miles according to GM), then you can do a normal EPA MPG segment and determine range extender MPG. Acutally do it twice for Highway/City.

        With those two numbers, Example: 40mile eRange and 48mpg fuel mileage, you can calculate exactly how much fuel you will burn in your personal usage pattern, what your total highway range is etc....

        Silly schemes of average the number together based on arbitrary condition quoted in this thread so far and coming up with numbers from 100 MPG to 400 MPG. Tell you nothing, only confuse and obfuscate the actual meaningful data.

        About the only benefit I see to such schemes is more pork for GM in addition the Multi-Billion bailout GM is asking for, and the monster tax bonus to help move their $40K economy this could add a license to have some false advertisement to include phony baloney MPG numbers that don't make any sense at all.

        In the end. What this needs
        EPA electric Range (45 miles City/ 38 miles Hwy).
        EPA RangeExtender Mpg ( 48mpg City/ 45mpg Hwy).

        That is the only hones and useful way to report the results of testing. If you have a brain, you can figure out what kind of result this will give you. If you don't have a brain, well quote 100MPG to 400MPG as suggested elsewhere in this thread is only going to confuse you even more.
      • 7 Years Ago
      Sadly, even listing seperately for electric-only and ICE only won't always give an accurate picture. The Aptera Type 1h apparently cycles its fuel engine even during the initial electric-only phase, starting with a fully-charged battery.

      As the battery becomes more depleted, the engine cycles on for longer/more frequent periods. In effect, there is no specific limit in miles during which the car runs solely from the battery with no generation from the ICE.

      From Aptera's website:

      "With the Plug-in Electric Hybrid version of the Aptera(typ-1h) the mileage of the vehicle is difficult to describe with one number. For example, the Typ-1h can drive 40 to 60 miles on electric power alone. Perhaps for such a trip, the engine may only be duty-cycled for a few seconds or minutes. This would produce a fantastic number, an incredible number that, though factually true, would have no useful context, i.e. it's just a point on a graph.

      An asymptotic decaying exponential is an accurate way to describe the fuel mileage of the Typ-1h. For example driving say, 50 miles, one might calculate a MPG number that's 2 or 3 times higher, say, 1000 MPG. As battery energy is depleted, the frequency of the engine duty cycle is increased. More fuel is used at 75 miles, the MPG might be closer to 400 MPG. Again, we're using battery energy mostly, but turning the engine on more and more. Just over 100 miles we're just over 300 MPG, and just beyond 120 miles, we're around 300 MPG."
      • 7 Years Ago
      The solution is very simple. The EPA rated an EV's mpg by mpg equivilant. Do the same for cars like the Volt; you just need to add the gallons of gasoline used to the "gallons" of gasoline equivilant used.

      So, the Volt uses something like 10 kwh for a 40 mile journey. Since a gallon of gasoline holds the equivilant to about 33kwh, that means the Volt used about a third of a "gallon" to travel forty miles.

      That means it gets around 120 miles per "gallon."

      Now, (according to the information provided in this blog post) the EPA test is 46 miles, leaving 6 miles not in EV mode.

      Let's suppose that the car gets 50mpg in this mode. That would mean that 85% of the test is 120mpg and 15% of the test is 50mpg.

      For the first forty miles you would use 1/3 a gallon of "gasoline" and .12 gallons of actual gasoline for the remaining six miles. So....forty six miles and .45 gallons of gas.

      That comes up to the grand total of 102 miles per gallons equivilant.

      So, assuming my math is correct, the EPA rating for the Volt (in my opinion) should look something like this:

      FULLY CHARGED

      City: xxx mpg equivilant

      Highway: xxx mpg equivilant

      Combined: 102 mpg equivilant

      EMPTY/HYBRID MODE

      City: xx mpg

      Highway: xx mpg

      Combined: 48 mpg
        gpmp
        • 7 Years Ago
        Well put. This is probably as close you're going to get to a electricity vs. gasoline comparison.

        It would also be the way to calculate an electric only vehicle as well as a hydrogen fuel cell car.
      • 7 Years Ago
      Confirmation that the EPA is manned by brainless morons.
      Their own commuter trip stats clearly prove a car like the Volt would achieve over 250 MPG while commuting, which accounts for fully half our gas usage. And that's not allowing
      for any workplace recharging, which is totally absurd. My estimate is tha the Volt will achive at least 250 MPG overall and that it could easily top 400 MPG with a few reasonable assumptions. This isn't rocket science, EPA folks. Look at you own statisitcs and stop trying to apply inappropriate mileage test loop results - they are totally meaningless when dealing with plug-in hybirds. Jeeez!!!! That's our tax dollars in action.
        • 7 Years Ago
        @ Snowdog,

        GM's own estimates put the range extender calculation at hundreds of miles driven the way it's built. Not arguing with you, but it's unrealistic to test the vehicle in a way consumers would more than likely never drive it. At least, that is my understanding of what the controversy is.

        The problem isn't so much, "hey, the EPA said I would get lower than I'm getting" (when's the last time that DIDN'T happen?). I think the problem, aside from GM's marketing department having a cat-turd fit, is misleading people from thinking this vehicle isn't worth the $40,000 price tag (that's completely up to the end user to decide). It'll also redirect a large number of potential Volt customers toward Toyota's dealerships even though the Volt is nothing like the Prius. Most consumers are ignorant. They see the mpg, they see the dollar amount and make a large percentage of their choice based on that. That's the current trend with Prius sales. There are vehicles that make more sense than the Prius, but chalk one up to Toyota's marketing for taking advantage of folks. Again.

        I still think Lutz should've kept somewhat hush on this one and let fuel cells, two-mode hybrids and other GM tech take the spotlight until at least the Volt was proven beyond concept form. As it stands, everything--and perhaps even, everyone--seems to be working against it, starting with Lutz' big mouth.
        • 7 Years Ago
        Here lies the complete absurdity of your position (and many others here) and the Justification for calling this car exactly what it is. An electric car with 40 mile range and 48mpg range extender. That is all anyone needs to know to figure out how it will work for them and their usage pattern.

        You quote numbers from 250mpg to 400mpg. These are completely meaningless and arbitrary. This should highlight cleanly the utter foolishness of trying to use such loaded arbitrary numbers for the rating of this vehicle. This tell you nothing!

        Hey why stop there? In the last 2 months I only had one day trip over 40 miles. I estimate by these hair brained methods my MPG would be 2000mile/.25Gallon = 8000mpg.

        There we go. 8000mpg. That's what the EPA should say.

        Getting a clue yet what the problem with this is? Probably not.

        If I tell you it gets 100mpg or 250mpg-400mpg like you claim or 8000mpg like the above. They are all arbitrary, meaningless numbers, that don't tell anyone anything.

        It is an electric car with a range extender. It gets 40 miles electric range first, then 48mpg on the extender after that. These numbers tell you everything you need to know and are accurate and honest.

      • 7 Years Ago
      It's *NOT* a 100 mpg car. It's a 48mpg car with a 40 mile all-electric range. You cannot represent what a PHEV does with one number. The EPA number is just fine; it simply needs to be displayed with the electric range. For example:

      "40 miles electric, then 48 mpg"

      Not particularly challenging. I've seen a more concise, but more cryptic, terminology, as:

      "48mpg PHEV40".
        bluegrassguitar
        • 7 Years Ago
        That is a good way to provide all the information necessary. Like a lot of us, my daily driving is under 40 miles. If I go on a long road trip, I will probably use another all-gasoline powered vehicle anyway.
      • 7 Years Ago
      Am I missing something? 10yrs ago the electric car went 100mpg. Now the new Volt can only go 40mpg? Have we gone back in time?? What have we learn in the past 10 years? I think the oil lobbyist still got their hand in the GM pocket to limit the distance.
      • 7 Years Ago
      Interesting that the range extender MPG is identical to the current EPA MPG for the Prius. Add 40 miles worth of LiOn battery to the Prius & you have the same thing right now. GM spent all that money & hype, has no improvement over currently available technology!!
      • 7 Years Ago
      In my opinion, I think they need to evaluate the mileage of the gas only mode and the recharge demands from a dead battery (or whatever the manufacturer certifies as drained). My reasoning?

      My daily drive is 112 miles (I know it is too much, don't get me started on that, want to buy a house?) . So if I saw the following rating I can make a decision:
      40 mpg/40 mEV (20 kWh)

      Ok, this would tell me that I can go 40 miles in EV mode from a fully charged battery. That means my daily drive is 72 miles at 40 mpg or 1.8 gallons of gas (about $7 in gas). If the recharge to full is 20 kWh then that cost to me is (about $2 in electricity). So my cost is $9 to get to work and back. Now I compare to my current car at 35 mpg (about $13 in gas), a new Diesel car at 50 mpg (about $11 in gas) or to a competitors PHEV at 44 mpg/35 mEV (18 kWh) about ($8.30 in cost).
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