• Aug 26, 2010

Translogic Episode 5.4 – Click above to watch video after the jump

One of the last big technical questions about the 2011 Chevrolet Volt is how much gasoline it will consume when the engine starts up to sustain the charge of the battery. Since the beginning of the development program back in 2007, General Motors has remained extremely reluctant to discuss details about the Volt's fuel efficiency, but a few days ago, the world got its first hint from an outsider.

Previous media drives with the Volt were done with 65 percent calibration level prototypes and we didn't get to see any of the mileage data on the displays. A team from our sister publication, Translogic, recently tried out a newer pilot production car at GM's Milford Proving Ground during a video shoot. Once they ran the battery down, the car continued for another 16.1 miles and apparently used 0.59 gallons of fuel for an average of just 27.3 miles per gallon. Needless to say, that's nowhere near the 50+ mpg that had been surmised from the big 230 mpg announcement a year ago. Read on after the jump for an analysis of what the video crew experienced, as well as the video itself.



[Sources: Plug In Cars, GM-Volt, Translogic]

Chevrolet spokesman Rob Peterson is now denying that the Volt will get sub-30 mpg results in normal charge sustaining driving. According to Peterson "As you can tell from the video itself, the AOL Translogic team ran a battery of aggressive tests with the vehicle including extensive use of Mountain mode, time trials [0-60 mph], [and] aggressive driving maneuvers."

As we are well aware by now, the composite fuel economy for any type of plug-in hybrid vehicle is highly dependent on the driving cycle (how far you go past the charge range). Sticking close to the charge range will obviously realize some huge numbers, but once the engine is running, the numbers drop off quickly. Normally, when the Volt goes into charge-sustaining mode, the engine generator does not re-charge the battery, it just maintains it at 30-35 percent charge. Because the engine/generator only produces about 70 kilowatts, charging the battery back up would require producing the power needed for driving, plus additional power to replenish the battery. This would consume much more energy than than just sustaining the charge and waiting until the car is plugged in to charge it back up to full.

However, if the driver requires some extra power for acceleration or hill climbing, the battery can run down below 30 percent and the range extender will recharge it back to that level. Obviously, that will have the engine running harder – and using more fuel – to maintain the battery.

Going beyond this the Mountain mode increases the battery buffer up to 45 percent so that the Volt will have full power capability when climbing into the mountains. Peterson confirmed to AutoblogGreen this morning that if the driver engages Mountain mode when the battery is still above the 45 percent threshold, there will be "no change in behavior" other than the engine starting sooner as the battery drains. However, if the battery is already very low (as it was during the testing in the video), the engine/generator will start up and actually work to charge the battery back up to 45 percent and then maintain that level.

Ideally, if an owner is expecting to do some mountain driving, he or she would engage Mountain mode before the battery has already been drained. In this scenario, the powertrain will use more fuel as the battery is maintained at a higher level but the engine will not work as hard to recharge it. The battery will also be able to recover more energy from regenerative braking during downhill sections, partially compensating for the extra fuel used during climbing. Just driving around on level ground with mountain mode engaged from a low battery state of charge along with the air conditioning during a humid Michigan summer is a worst case scenario for Volt energy efficiency.

One other item mentioned by Peterson has to do with the numbers used to calculate Translogic's observed 27.3 mpg figure. That magic number was derived by a GM-Volt.com reader that did a screen capture and worked backwards from the 43.7-mile electric range and 59.7 mile total driving range. The problem is that the video crew didn't actually drive that full distance. The energy meter had not been reset prior to the evaluation drive, and as a test vehicle, it's anybody's guess what the vehicle was called upon to perform prior to the video shoot. Further, it's worth noting that EPA test cycles don't include anything close to full-on 0-60 mph acceleration or maximum braking or handling maneuvers. Anyone with a newer car who has a trip computer should be well aware that looking at the mileage readout at any point in time is not necessarily representative of anything over a longer period.

The bottom line is that this video was one snapshot in time without context and we still have no idea what the real world efficiency of a Volt will turn out to be – and we likely won't until at least sometime in late October or November. As the sticker says and the video below proves, "Your mileage may vary."






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  • 82 Comments
      • 4 Years Ago
      I don't understand why it's such a complicated issue. A car should be measured on how much gas it takes to travel a certain distance. Granted, the Volt might not use any gas at all to travel up to 40 miles. So perhaps to level the playing field, they should measure the gas mileage over a long period of time, such as 200 miles. I'm not great at statistics, so I'm sure my logic is flawed. Do I just not get it?
        • 4 Years Ago
        A 200mi trip is not typical so that figure doesn't give you much meaningful info. Since the car is likely to be driven as a commuter car and plugged in each night, the figures will be much, much higher than what one would achieve on a 200mi trek. Fuel usage could be quite minuscule if your commute is below 40mi(covers 80%+ of drivers) and you plug in every night.

        Do you see why a single figure for a long distance drive isn't accurate?

        I definitely see the dilemma that the EPA has here and I don't envy their job trying to sort it all out.
        • 4 Years Ago
        @montoym

        Sure, I see why it's not accurate because most people won't care about a 200mi trip with a car like the Volt. But if you're only talking about commuter-length trips, then I guess a traditional MPG measurement just goes right out the window.

        Maybe they'll have to do like an "asterixed" MPG list, like the movie "61*" :-)
        • 4 Years Ago
        I think the EPA should just add another column. So it would be like 40 ME (miles electric)/ 25 MPG city/ 35 MPG highway. Something along those lines.
      • 4 Years Ago
      The highest point in Michigan is 1,979 feet and is nowhere near the Milford Proving Grounds - that means their mountain-mode driving was anything but. If you live anywhere but the plains you'll encounter hills at least as big they did and A/C use was likely common across the country all this summer.

      What was called 'worst case scenario' is pretty normal driving conditions for most people.
        • 4 Years Ago
        Mountain mode causes the ICE to turn on earlier, it reduces the battery-only range by about 30% if you engage it in regular driving. Even if you never encounter a hill.

        This is explained in the article.

        So it may not be worst-case, but it's not normal either.
        • 4 Years Ago
        Agreed, RTFA.

        The worst-case scenario was described exactly as such, "Just driving around on level ground with mountain mode engaged from a low battery state of charge along with the air conditioning during a humid Michigan summer is a worst case scenario for Volt energy efficiency."

        So, the battery already has to be at a low state(which means you are/were driving it hard since it won't drop below 30% normally, but can if needed). You also had to have Mountain Mode engaged(which will run the engine harder to bring the charge to 45% rather than the normal 30%). And you have to be running the A/C as well(which presumably they were during the Michigan summer).

        Driving up a mountain pass is comparatively easy, it certainly takes more power, but those combined situations will be far more stressful on the engine. The only worse scenario I could think of is something like taking the car autocrossing (running the battery well below 30%), then loading up 500lbs of gear and taking off up a 40+mi constant-grade mountain pass while running the A/C full blast. Not exactly a typical drive in my eyes.

        As I mentioned in the related thread the other day, if your typical driving is similar to how the tester drove this Volt, then you might experience similar mileage. But, I doubt that's how 90%+ of owners will drive and those 90%+ will achieve better mileage, some much more so.
      • 4 Years Ago
      The point of the drive wasn't to get a mpg rating.

      The point was to show how it drives.

      And it does very well.

      The rest of you have no clue about what you post.

      If the Volt gets a lousy mpg rating (which I doubt) then flame on. Until then stop making fools of yourselves.
        • 4 Years Ago
        Sure, the _point_ wasn't to get an MPG figure, but there it is.

        It would be absurd to suggest that 16 miles of driving, especially performance testing, gives a realistic picture of the real-world average MPG.

        The number itself, though, was honestly derived. It just has to be taken with a grain of salt. Or maybe a whole shaker of salt. Or the Bonneville Salt Flats.

        What I don't have a clue about is how that adds up to everyone but you being a fool.
      • 4 Years Ago
      So much hate for the Volt.
      • 4 Years Ago
      What are we looking for?

      MPG of the vehicle or mpg of the gasoline motor?

      MPG of the gasoline motor is pointless because it isn't always running
      for every driver. Even then, it supplies no mechanical energy to drive the wheels, just
      charge a battery which has prior that used no gasoline.

      Because the volt uses both gas and electricity on an mutually exclusive basis, focusing on one metric isn't a valid/fair assessment.
        • 4 Years Ago
        TonyInMI,

        In the first few year, this will NOT be a mass market vehicle and GM is not planning on producing high volumes. Besides being a halo car for GM, it will be used to establish the technology while further developments allow them the start lowering the price. The plan is to eventually get the price down to where it does make straight economic sense and then can become a mass market vehicle.

        In the mean time, this is a cell phone circa 1988. The tech is there, but the price is still too high for most people. Just wait a couple of years.
        • 4 Years Ago
        In reality the little motor will be running all the time - unless all you do is unplug it, drive around town, and plug it back in. If you want this functionality for $40,000 go for it. Mass market appeal? NO WAY.
        • 4 Years Ago
        Wow, you've got a point there... except for the fact that the scenario you described is almost exactly what a huge majority of cars experience every single work-day... maybe with a few miles for lunch in the middle.

        This isn't a track-day car. But then again, most cars aren't.
      • 4 Years Ago
      Some people are forgetting about the new smart electric readers that will increase your bill during periods where you draw more electricity than surrounding homes. When the average home is drawing less than a kilowatt during the night and you are drawing 15 amps for 8 hours you are going to get billed more. You also do not get a special EV rate without paying for it in other areas. If the rate is state subsidized you will pay for the lower rate in higher taxes.

      The $.12 per kilowatt hour average price is complete BS because it does not include delivery charges, transmission charges, and other taxes and fees. Take your actual bill and divide it by your energy use and you will get a real cost. For most people it is closer to $.30 per kWh. In New York people pay closer to $.50 per kWh.

      Don't you worry if more and more people buy EVs the utilities and government will find a way to make the cost of charging your car equal to filling up a tank of gas. We get cap and trade and you'll be looking at a quadrupling of your electric bill.

      Another popular misconception is the average daily commute. Many people drive less than 5 miles a day to work and many people drive more than 40. What about getting stuck in traffic? More important than the mileage of your commute is the time it takes you to get to work. If your commute is ten miles but it takes you an hour to travel that ten miles you are going to use a lot more energy than a person whose ten mile commute takes ten minutes.

      My daily commute is 76 miles total. Best case scenario is that I drive on battery power all the way to work but have to drive on range extender mode all the way home since I will not be able to plug in my car while I am at work. How that works will have to be tested. Essentially the Volt will be saving me about half my current gasoline use. However adding the purchase price of a Volt, which is double the cost of my current 30mpg car, the gasoline savings will never pay for the upfront cost over the vehicles life. Kind of like solar panels and wind turbines.

      The range extender does not give you much better than 30mpg while it is running. The simple math of the Volt's proposed range and gas tank size proves the calculation. Simple logic says that the Volt is not a very good solution. The problem is that people tend to not want to believe simple logic.
        • 4 Years Ago
        enbadesign, I think your $0.30/kWh is completely out of whack. Here's my real-world electricity bill:

        600 kWh @ $0.12333 = $74.00
        537 kWh @ $0.10990 = $59.02
        Base charge = 4.54
        Meter charge = 2.19
        Distribution charge = $1.87
        Sales tax = 1.41

        Total kWh: 1137
        Total cost: $143.03

        Cost per kWh: $0.126

        I've never heard of a scheme that charges you more per kWh if you're using more electricity than your neighbors. Do you have an article to reference that?

        Regarding your "take 1 hour to drive 10 mile commute" scenario - yes, that'll take more energy due to AC, radio, etc. But that applies just as well to a gas vehicle as an electric one, so I don't see how that's really a factor to consider.

        Also, it's NEVER cost-effective to replace a working vehicle with a new one just to save on fuel costs. Even if you were driving a Dodge RAM 1500 HEMI that gets 12mpg, you'd end up paying more if you sold it to purchase a Prius. (Per the EPA's website, the Prius costs $1721 less per year. At $22800 MSRP, it would take you 13 years to make up the purchase price.) You get the fuel-efficient vehicle only when you need (or want) to get a new vehicle anyway.

        And finally, if we take your 76 mile commute, 40 miles of that would be on electricity and cost $0.12/kWh * 8.8 kWh = $1.056. 36 of that would be on gasoline and cost $2.60/gal * 36 mi / 30 mpg = $3.12. Total cost, $4.176. Compare that to your gasoline-only 30mpg car, and you get $2.60 * 76 / 30 = 6.59. I'm not saying that's a big difference, it's only $603.50 per year. But if your current car were totaled in an accident tomorrow, and you were shopping for a $40k vehicle, the Volt would have lower running costs per mile than some other $40k, 30mpg vehicle you might be looking at.

        Now the question that raises - is the person in the market for a $40k car (Lexus IS, Audi A4, Infiniti G, Merc C Class, BMW 335i, etc.) going to pay much attention to the Volt, even with it's gee-wiz tech?

        ps - having done some math recently, my calculations showed a 6 year ROI on solar panels if subsidized, 11 years if not.
      • 4 Years Ago
      I don't understand how this other site and autoblog function under the same corporate roof.

      Even if AOL wants to do that full editorial control should be with Autoblog.
        • 4 Years Ago
        Correct -thats why i am suggesting that all editorial control should be with Autoblog and that all other AOL Autos people should answer to them.
        • 4 Years Ago
        I believe AOL owns them all, no?
      • 4 Years Ago
      GM at it's best, trying to spin the story.
        • 4 Years Ago
        Where is the spin? GM explained the difference between EPA testing and performance testing. Jeremy Clarkson made the Tesla Roadster run out of juice after 40 miles on a track but Fifth Gear made a 170 mile trip of enthusiastic driving. And Ford GT gets 4 mpg on track but EPA rating is 12/19. If Ford came to say that 4 mpg is not representative of normal use would that be spin too??? Fuel consumption certainly varies!
      • 4 Years Ago
      Would GM go through all of this just to have the Volt hit 27mpg? The obvious answer is no, but that won't stop the Toyota driving, GM haters from wishing so.
      • 4 Years Ago
      Autoblog=Enquirer





      • 4 Years Ago
      Besides, 27mpg from spirited driving is actually not too terrible.
      • 4 Years Ago
      Huh?

      16.1 miles divided by 0.59 gallons is 27.3 mpg. There's no "working backwards" from the 43.7 mile electric range and 59.7 mile total driving range; the difference of those is 16 miles, the same distance shown by the computer to have been traveled in charge-sustaining mode. Or, you could just read the 16.1 miles right off there ... duh.

      It's a 3500-pound car; why would anyone expect it to do better than 30 mpg, especially in this sort of driving? There's no magic to the electric drive; the energy still has to come from somewhere, and it takes a lot of energy to move all that weight. I would not be surprised at all if later tests reveal similar results.

      From what I can tell, the video crew did indeed drive the car for 16.1 miles while the engine was running, during which time 0.59 gallons of gas were consumed. It's not rocket science to derive an MPG number from that.
        • 4 Years Ago
        Wow, I really earned an epic number of vote-downs with this one. Inexplicable.

        There's a world of difference between the accuracy of a statistic and its predictive value. The 27.3 figure is perfectly accurate but of essentially no predictive value.

        In other words, we're no closer to a realistic estimate with this number than without it. It's no more complicated than that.
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