• Oct 11, 2010
2011 Chevrolet Volt – Click above for high-res image gallery

Until today, talking about whether the internal combustion engine (ICE) in the 2011 Chevrolet Volt should have a direct mechanical connection to the wheels was an interesting thought experiment. Sure, there were hints and patents that suggested that the ICE could drive the wheels, but General Motors kept saying its "extended range electric vehicle (ER-EV)" was just that: an electric car with a gasoline-powered generator on board. Guess what?

GM has now confirmed, late in the game, that the Volt can, in some situations, use the ICE to power the wheels. This came to light after Motor Trend was allowed to test the car for three long drives and discovered:

However of particular interest, when going above 70 mph in charge sustaining mode, and the generator gets coupled to the drivetrain, the gas engine participates in the motive force. GM says the engine never drives the wheels all by itself, but will participate in this particular situation in the name of efficiency, which is improved by 10 to 15 percent.

This is exactly the opposite of what GM has been saying for years – most recently in June, when GM spokesman Rob Peterson told AutoblogGreen that there was no mechanism in the Volt to drive the wheels even if the engineers wanted too. Or, at least, that's what we heard. Peterson told AutoblogGreen today that the "news":
is consistent with everything we've said to date. The new "news" is that we can tell the complete story as our key patent has been allowed by the US patent office. The Volt is an electric vehicle with extended range as the Volt has full battery electric performance at all speeds when there is charge in the battery.
Click past the jump for more.



[Sources: General Motors, Translogic, Motor Trend, Green Car Advisor, The Car Connection, Popular Mechanics]

So, from what we know now, the Voltec drivetrain has a single planetary gearset, a pair of electric motors and, of course, the gas engine. The systems central sun gear gets power from the 149 horsepower electric motor at all times, while an outer ring gear gets power from the engine or the smaller electric motor when needed. The planet carrier then sends power, from whatever source, to the wheels. GM global vehicle chief powertrain engineer Pamela Fletcher told The Car Connection that the two-motor powertrain gives the Volt three more miles of electric-only range than would otherwise be possible.

Like we've said before, it makes sense for the Volt's engineers to design the powertrain to be the most efficient they can, and if they think that some gasoline assistance will help buyers choose this partially electric car, then that's fine. Labels are just labels. But what will GM's marketing arm, that's been so preoccupied with saying the Volt is an ER-EV that's totally different from all other cars out there, do now that we know the Volt is pretty much a plug-in Prius with a bigger battery pack? For what it's worth, some of the first real-world Volt tests are showing around 33 miles in EV-only mode, compared to the plug-in Prius' 13 or so. Thanks to David M. for the tip!


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    • 1 Second Ago
  • 67 Comments
      • 4 Years Ago
      ICE's are most efficient at WOT and high speeds, so it makes sense.

      The generator, motor, and engine are connected at a planetary gear system, so after a certain speed the engine would have no choice but to contribute to the drive mechanism. Planetary gears are hard to fully comprehend but look into it and you'll start to get it.
        • 4 Years Ago
        yes it makes sense. that's not the issue, the issue is that it doesn't make sense that gm has been claiming that the range extender was just a charger, this information pushes volt even more into traditional(by now) hybrid territory.

        doesn't help that the electric only range has been cut down and down almost monthly as the release nears.

        makes the leaf that much more of a 'new' product.
        • 4 Years Ago
        But couldn't they also just have the ICE rev higher so the generator generates more electricity?

        But I suppose at that point it would just be more efficient to have the ICE power the wheels.
      • 4 Years Ago
      The Volt has no transmission; can it only connect at highway speed? This is still not clear, nor does it match some of the diagrams of the Volt's systems that are out there.
        • 4 Years Ago
        James, you just described the Prius HSD.
        • 4 Years Ago
        It seems that a lot of people forget that GM is a global company, rather than being stuck in 55mph-limited states.

        How else is it going to be usable in Germany? If it won't go 100+ mph on the Autobahn, GM won't be able to sell any Opel Amperas, which means they have more difficulty recouping the technology investment.

        To run 100 mph on battery wastes fuel compared to the direct drive coupling, so GM's approach makes a lot of sense. Use the most efficient power source available for the speed of the vehicle.

        Being able to sell Volt technology on 3 continents means they can recoup the investment and move the the second generation sooner, rather than later.
        • 4 Years Ago
        The output shaft is basically replaced by a planetary gear system that allows for the connection of either the electric of gasoline or both engines at once. It's identical to an automatic transmission set-up, but an exceedingly simple one without multiple output ratios, able to take input from two sources.
        • 4 Years Ago
        I believe (although I could be wrong) that the Prius still has a multi-gear transmission (or CVT), whereas the Volt has a single gear ratio.

        So it's not quite the Synergy, and it's more of a gas-assisted boost (in charge sustaining mode).

        Technically, I'd say the Volt is a gasoline-assisted EV, and the regular Prius is an electrically assisted ICEV. The plug-in Prius seems to be somewhere in the middle.

        Regardless, it's such a fine distinction that they may as well slap a "Better Engineered Hybrid" label on the car, and be done with it.
        • 4 Years Ago
        No, the Toyota HSD system does not have multiple gears, or a CVT in the traditional sense. In fact the description of the Volt system sounds very similar to Toyota's.
      • 4 Years Ago
      Just sell the damn car so all these early adopters can drive down the cost and extend the range of the battery in the all ev I buy 10 years from now PLEASE.
      • 4 Years Ago
      I always wondered why the Volt had such a large engine if it was only there to charge the batteries. One would think a two cylinder (such as the one found in the Fiat 500) would be sufficient to charge the batteries and would be even more efficient.
      • 4 Years Ago
      Well, that explains why there is so much stuff under the hood.

      I saw one locally and the stuff under the motor and inverter was enormous. It was clearly big enough that it could contain a transmission, I guess now we know it does.

      I think this is very much a smart move, it will increase gas-mode mpg significantly.

      It also really shows how smart Toyota was with the Prius. Series-mode just doesn't make sense from an efficiency standpoint. I guess GM looked at it and decided the same thing.
        • 4 Years Ago
        No, I don't think it has changed. The only way it changed in a way that affects the customer is the 33 mile thing. If it's really going to be typically 33 mile EV range, that impacts the customer.
        • 4 Years Ago
        You sound like you're still convinced the Volt has changed. It hasn't -- what's changed is what GM is allowed by its lawyers to declare to the world.
      • 4 Years Ago
      Planetary gear set on the engine output shaft? Where have I heard that before...

      If I were Toyota I would be reviewing how this system is laid out very very closely...
      • 4 Years Ago
      but does this change the tax credit? thats the important question.
      • 4 Years Ago
      This is how it works

      When you have used up all the battery 35- 45 or so miles.

      Then it starts the engine to start keeping the batteries up to charge.

      At above 70MPH the engine also helps the motors because its already running to charge the batteries.


      Now if are still running off batteries 20 or so miles in your trip and you go above 70 MPH the engine will not turn the wheals because it is not charging the batteries.

      So the engine ONLY turns helps power the car when your have depleated the battries.

      So the Volt is pure electric at times. But when you use up the battries its also a hybrid.

      Its a MIX but I think GM did it right why not use the engine if you have it running to charge that bats anyways. It uses the extra power makes scene.

      • 4 Years Ago
      Oh, well that's interesting. Raises quite a few questions since we knew otherwise before.

      So, I'm a little confused...the engine, while powering the generator, will also displace some power straight to the drive train? But it never takes over from the generator completely?

      Sounds complex...but if it works and is efficient, I'm all in.
        • 4 Years Ago
        If it works, is efficient, and reliable ...

        But I guess it being a planetary "transmission" that connects the two motors to the output shaft, that's a tried and true system, as long as regular maintenance is convenient to do.

        (It's a real pet peeve of mine when an engine is difficult to service. The oil filter in my Acura is located right above a cross brace and next to the header, so when I change it it generally pours all over the frame and oil drips from it for the next month which makes me paranoid each time that the drain pan bolt is not screwed on right. And BMWs and MB engines are so designed to be a chore to work on. Saabs are so convoluted it's insane.)

        • 4 Years Ago
        The prius does the same thing - it uses a set of planetary gears to connect the engine, the wheels and the two electric motors.

        It sounds complex, but it is amazingly clever and simply.

        This guy has an app at the bottom of the page to show how it works

        http://eahart.com/prius/psd/
      • 4 Years Ago
      Oh, please!

      Government Motors was all to happy to showcase 230 mpgs and to claim the sky with the VaporVolt, but the engine (which is twice the size needed to do what it is said to be doing in the Volt) wasn't going to direct drive the wheels?

      I'm sorry, but the script out of the Hive of Government Motors has just been a bit too precious for me. Having for the better part of a decade done really nothing on the hybrid front other than to have assistive start and really lame attempts at real hybrids, we are now to assume that this company is SERIOUS about building an electric vehicle with gasoline power assist?

      The script has changed constantly out of Government Motors about the VaporVolt - 100 miles down to 40 and then to restate to possibly 25 miles to 50 miles and then now to the vehicle can drive on gasoline. What hasn't remained constant is the commitment of this company to deliver a product at an affordable cost and to do it so that the vehicle makes money for the American and Canadian taxpayers. And while we've "donated" $50 billion to a company to big and too stupid to succeed, we still have to prop them up with $7,500 tax credits (plus the cost of the annual interest payment on that debt) to move their iron. Notice you aren't hearing any Government Motors Executives leading the charge to say "we'll pay the $7,500" in what would have been a remarkable admission that adults are now running GMC.

      I suppose these constantly changing stories about the VaporVolt capabilities are supposed to make us feel better about chosing a VaporVolt over a Nissan Leaf, but Nissan will supply me with a gasoline powered loaner car if I need to go somewhere for a distance and it won't be a Chevrolet Aveo or Chevrolet Cobore. It will likely be a fuel efficient and space efficient Versa which won't win a beauty contest, but is still superior to what GMC has in that segment.

      I wish GMC all the luck with their gimmick because they'll need it. There hasn't been a demonstrated level of engineering competence on display from this company in four decades. And purchasers of the VaporVolt need to remember that GMC's engineering department is as competent as the one that produced the Trabant in the other Socialist regime.
      WinXP
      • 4 Years Ago
      it's legal to drive 70mph on the 10 freeway going to and around palm springs. though the 65mph sign has never slowed me before.
      • 4 Years Ago
      what happens at 88 mph?
        • 4 Years Ago
        Sorry forgot to add. The turbo on the turbo model will not, I repeat NOT be directly linked to the motor.
        • 4 Years Ago
        you get a speeding ticket
        • 4 Years Ago
        1.21 gigawatts.
        • 4 Years Ago
        Unless you're in Texas
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