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2011 Chevrolet Volt – Click above for high-res image gallery

Back in 2006, when the Chevrolet Volt was first conceived, its extended-range electric (ER-EV) powertrain was originally dubbed E-Flex as its configuration was designed to be flexible. The only part of the system that was constant was the electric drive and the presence of a battery. The architecture was designed so any type of powerplant could be used as a range extender, and over the last three years concepts have been shown with flex-fuel three-cylinder turbos, inline-four diesels and hydrogen fuel cells.

Ultimately, powertrain chief engineer Larry Nitz and his team opted for a normally aspirated 1.4-liter inline-four for the first generation Volt because it offered the best combination of cost and efficiency. However, while working on the first-generation Volt, work on the second-gen model has been happening in parallel. Way back in May 2007 we talked to then-VP for R&D Larry Burns about using an HCCI engine for the Volt since it could be optimized to operate at steady state speeds. He agreed that was certainly one possible direction.

Right now, the top priority for the second-generation Volt is driving down the cost of the powertrain, including the battery. Although automakers are always reluctant to talk about parts pricing, GM's project management VP, Jon Laukner, has hinted on more than one occasion that the Volt pack costs somewhere in the $600 per kilowatt-hour range or under $10,000 for the 16 kWh unit. The goal is to get that cost down below $400 per kWh in the next few years and a combination of increased volumes and LG Chem launching cell production in western Michigan will certainly help to achieve that.

Reducing the cost of the range extender will also play a part. GM's VP of global vehicle engineering, Karl Stracke told Inside Line that smaller range extenders in the 15-18 kilowatt range are part of the strategy and either a two-cylinder piston engine or a single rotor Wankel are possibilities to replace the current inline-four. Volt communications manager Rob Peterson confirmed to Autoblog that a number of different variants are being evaluated, but he wouldn't say if any particular direction has been selected yet.

Powertrain engineering consultant FEV has recently been showing off an ER-EV Fiat 500 with a Wankel range extender. While Wankels are not known for fuel efficiency (quite the opposite, actually), a modern direct injected unit for this type of application could be highly optimized to provide acceptable performance and consumption. A Wankel also has the advantage of being both very compact for its output and vibration-free, making it well suited for this type of application. With the first-generation Volt only expected to have about a three-year life-span, a final decision will likely be made very soon.


  • 11/29/09 7:17:39 -- Los Angeles, CA, U.S.A Vehicle Chief Engineer Andrew Farah and the new Chevy Volt during the Dodger Stadium ride and drive.

Photos Copyright ©2009 Sam Abuelsamid / Weblogs, Inc.

[Source: Inside Line, General Motors]


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    • 1 Second Ago
  • 56 Comments
      • 4 Years Ago
      It would be nice to see some of the more recent ideas for rotary type engines to be investigated by GM. For example the Libralato engine runs on a very efficient Atkinson cycle and has a very high power density:

      http://www.libralato.co.uk/technology.html

      The Rand Cam engine also is a rotary type engine with high power density:

      http://www.regtech.com/Radmax_Technology/

      In addition, there's the Nutating Disc Engine, Dynacam, and a host of others. It seems like now is the time to look at alternative rotary type ICEs to see which has the right balance of power density, efficiency, and reliability.

      • 4 Years Ago
      They really need to pick a direction and go with it.

      Maybe Diesel, Maybe 2-Cyl, Maybe Rotary says they Certainly have no clear goals. Without a clear goal it will be hard to achieve anything. If Fuel economy in RE mode is important why is Rotary even on the list?

      15KW-18KW also shows them living in dreamland. Seriously is someone lacing their Wheaties with stupid?

      IMO as a city car the leaf wins with pure EV and more than double the EV range.

      The advantage of the Volt is that you can take it on a road trip. That advantage is nullified if you take it on a road trip and it limits your top speed to 55MPH to preserve charge or 45MPH climbing a long grade.

      If the Volt is too succeed, it has to be road trip worthy and behave like a normal car while doing it. To me that means cruise effortlessly at real highway speed (75MPH in my part of the world) and maintain that up passing zones on long hills. This will even challenge the current Volt with triple the power genset, but I believe it will pass the test for most. but 1/3 the power, forget it. Non starter. Borderline Idiotic.

      Seriously the info in this story makes GM look utterly clueless and direction-less. It's like they let the first day intern take the interview. They shouldn't let new VPs answer tech questions until someone with a brain tells them what to think.


        • 4 Years Ago
        I believe you are mistaken in how range extenders work.
        If you want acceleration, you tap the battery for the surge of power. The range extender keeps the battery topped up enough to do that, so it runs efficiently at a constant speed.
        So the Volt will use the battery only for a few miles, but will switch on the range extender when the batteries still have enough charge to help the range extender as needed.
        • 4 Years Ago
        Hey Joe,

        Yeah I know the current Volt will have a ~50KW genset and think that is a good choice with a healthy reserve for most situations. I think it was a good choice.

        I just think talk of 15KW gensets is largely nuts. People think that if a battery is involved, the laws of Physics no longer apply and the Genset power is irrelevant, which is not the case. You need a genset that exceeds your average power requirements, your usage pattern will determine by how much you need to exceed average power requirements.

        These tiny Gensets don't even exceed average power requirements for highway travel unless you keep it under the speed limit.
        • 4 Years Ago
        53 kW (71 hp) genset on the range extender.

        Don't get caught up in speculation on GM that is guaranteed to change.
        • 4 Years Ago
        you fail to appreciate the advantage of keeping things lean
        • 4 Years Ago
        @David.

        I think you are uninformed about how much power it takes to punch through air resistance at 75MPH. Hint it is more than 15KW.

        This is just flat ground cruising minimum CONSTANT power draw. You simply won't be able to sustain that cruising speed on a road trip with 15-18KW Genset because you have ZERO reserve capacity in the Genset going back into the batteries.

        IMO those are idiotic numbers that will never happen, it will be too much deficit on a road trip compared to a normal car where you can cruise all day 75MPH with the AC on and even up grades.

        I have even seen many people argue that the 50KW Genset (triple the discussion here) in the Volt is too weak, because hitting an ultra long running in RE mode will compromise their power passing on a long uphill grades.

        I think the Volt current genset will be fine because it has a lot of extra reserve over normal driving situations. It is a good thing they went this route on the first EREV as under-engineering with a 15KW genset would likely have killed EREVs forever after they got lambasted for poor road trip performance.

        My prediction on the next Volt Genset. Gas powered 3 or 4 cyl making similar power (maybe slightly less). Essentially none of the options bandied about this story. They are pure fanciful fluff.

        • 4 Years Ago
        Well, this is new territory. Anyone else know who the best engine configuration for a range extender, through experience and R&D? yeah, i thought so. I can't think of anyone who really knows.

        I'm figuring that the 1.4 is in the car currently as a means to make the car cheap. They produce those motors for pennies on the dollar. It's not ideal, but it means the car will be released in 2010, not 2012.

        I too am worried about the future range extender options. What if you have to climb an 8% grade for 5 miles, on a low electric charge? Most small-engined cars are at 50%-100% throttle then. For over $30k, this car better be able to pull that task off.
      • 4 Years Ago
      A 2 cylinder atkinson cycle boxer engine
      • 4 Years Ago
      Even when you spoon-feed them, it seems ABG misses the info:
      'GM is expected to launch the Volt in the territory of $35,000 (before federal and local tax incentives) in order to be competitive with the $33,000 Nissan Leaf battery-electric car that goes on sale in limited release in December.'

      http://blogs.edmunds.com/greencaradvisor/2010/05/volt-ii---a-5000-battery-pack-and-a-rotary-engine-range-extender.html

      This has a lot of consequences for the Leaf, as many Americans are likely to go for the increased range as long as it has not got too great a premium
        • 4 Years Ago
        That is the first I have seen of that price. Is that official from GM or just more speculation? If real that is good news for Volt sales.

        But if I was in the market for a plug in, I would still go leaf. Much longer EV range and zero ICE maintenance. I Drive less than 200 mile/week so even if the real world range of the Leaf is 50 mile it would be plenty for me and I can rent a car for road trips.

        • 4 Years Ago
        Who will buy the Volt, and who the Leaf, at these prices?
        • 4 Years Ago
        Even at $35k it's not a guarantee that people will go for the Volt vs the Leaf. If it is for a daily driver or second car, the AER of 100 vs 40 matters more than the range extender since most want to drive as much miles on electricity as possible (plus there's the maintenance thing like Snowdog mentions).

        If it is the only car and for a person with frequent weekend trips beyond 80-100 miles, then the Volt definitely makes more sense.
        • 4 Years Ago
        Over at Edmund's they say that they had an audience with the GM people, so presumably it is semi-official.
        It sounds as though it must be about right, if they hope to sell any against the Leaf.
        • 4 Years Ago
        Good job reading the freaking article :)
        If they can pull off $35000..... that's not bad at all.

        I think there's room for the Volt amidst the Nissan Mania.

        Hopefully this sparks a competitive green car price reduction war.
        • 4 Years Ago
        Martin said, "Who will buy the Volt, and who the Leaf, at these prices?" Not many as the production numbers are so low.

        Soon after the Volt day views, you will read these haunting words once again, "Volt sold out for 2011."
      • 4 Years Ago
      The question is who will be able to buy the Volt.
      With GM likely to lose money on the Volt for the forseeable future and a limited production run it will be mighty hard to get your hands on one. After federal incentives the vehicle cost 27.5K and tack on local incentives of several thousand and you have a 25K car that most everyone can afford.
      So until GM can cut the battery pack (and other hi price items) cost the Volt might not be a "mass" production vehicle if they are losing money on every sale.
      • 4 Years Ago
      A Rotary would be the perfect candidate. You want to talk flex fuel? How about an engine that can run off of gas, diesel, hydrogen, methanol, or just about anything else that combusts. It that isn't the perfect solution for a range extender I don't know what is. It's a shame so many people are ill-informed about Rotary engines in general.
      • 4 Years Ago
      @David Martin

      But Snowdog is correct in that it's questionable that even the current power of the engine is going to provide sufficient power at highway speeds, let alone a shrunken engine. Once the batteries get to 30% SOC the engine comes on, but the SOC window in the hybrid mode will be quite small, meaning that by far the bulk of the power must come from the engine.

      ABG had an article on a supposed "Mountain Mode" wherein drivers who know that they are going to be driving on the highway in hybrid mode can push a button and have hybrid mode be engaged at a higher (than 30%) SOC. Doing this could mean a smaller engine might work, but this shortens the AER. It's going to be interesting to see how the Volt performs--if GM doesn't get it right it will be disastrous, but I personally think that they will.
        • 4 Years Ago
        @Dave.

        On the previous page (Post 15 ATM) I simply work a back of the envelope type calculation based on Volts EV Range and 8KW capacity (assume 55MPH for range) and doubling of power required to go from 55MPH to 75MPH which is expected from exponential increase in drag. Precise calculations require numbers that are not available (and would be fudged even if they were).

        There are assumptions in their but they are likely not that far off. It gets us in the ballpark. The ballparks says 18KW genset is inadequate for highway use in the real world where people drive over the speed limit. Drag is exponential with speed, so even if my numbers are off it will only take a few MPH to make the same case.

        Here is something from a Volt Blog. Their highway numbers are higher than my working backwards numbers. My working backwards numbers were 22KW highway at 75mph. They just have 25KW highway without conditions. Note KWh should be KW.
        http://gm-volt.com/2007/08/29/latest-chevy-volt-battery-pack-and-generator-details-and-clarifications/

        "The engine’s job will be to maintain the battery at a SOC of 30%, and will do so by continuously matching the average power requirement of the car once it is turned on. Those energy requirements will roughly be about 8 kWh in the city, and 25 kWh on the highway."

        No matter what you look at, higher highway speeds will need 20KW of power to sustain them from the high drag unless you have exotic(Aptera) type drag (Volt doesn't).

        Even if you eek out some savings it should be clear that you are going to be on that edge with an undersized genset, versus something like the Lotus genset(only weighs 56KG) So what, you under-size to save another 15KG and compromise highway performance??

        That article IMO was very much random nonsense. 15-18KW gensets are only suitable for city cars.
        • 4 Years Ago
        @David.

        The 35KWs of the Lotus moves it from the ridiculous (15-18KW) in this article to the realistic. I think the Lotus RE is the best overall compromise I have seen yet in a minimal but at least realistic Genset. Best of all it supplies 15KW at low RPM (and presumable very quiet), so it would be ultra quiet unless you are pushing it, but at least you have the option to push it. If they get these into production, I could see it being the "Go To" Genset.

        With a weak 15-18KW genset, you are at the limits just on normal highway cruising where the engine would also be running at flat out max RPMs. It simply isn't worth the complaints and bad press on performance to go this weak for minimal advantage.

        As I have said previously, I expect a gas powered 3 or 4 cyl in the next Volt (or other EREV in North America for that matter).

        Solid, reliable, economical (with fuel and build), easy to tame emissions, with extra power reserve capacity. These advantages of the regular gas 3-4 cyl won't go away simply because Rotaries are cool, or Diesels has a small efficiency boost.

        I think GM chose well for thier first Genset and I expect something similar in the gen2.
        • 4 Years Ago
        @Snowdog,
        What I haven't heard discussed, or perhaps haven't understood, is how drag is taken into account in the calculations?
        • 4 Years Ago
        Dunno, it does seem difficult to do with such a small engine.
        Lotus however with their dual speed range extender which operates most of the time at around 15kw although also capable of 35kw specifies the same performance when you are using the range extender:
        http://www.greencarreports.com/blog/1034976_let-the-range-extender-wars-begin-lotus-unveils-tiny-engine

        Peugeot in their prototype fuel cell vehicle also seem happy that they can get acceptable performance from as small a power source as 17kw:
        http://www.greencarcongress.com/2009/12/fisypac-20091208.html#more

        Of course, we may not be being told the whole story, the GM for instance may have capacitors too for power surges, and it is quite possible that the car is not set up to cruise at 75mph which is draining, I suppose.
        Presumably all the engineers have not lost their marbles, and they are as aware as anyone else of the limits of the engine and that they can't totally ignore performance.
        • 4 Years Ago
        As Snowdog notes, It's primarily a function of highway speed.

        Re-institute the National Maximum Speed law and you largely solve the problem of a "too-small" range extender.
        • 4 Years Ago
        @Snowdog:
        Fair enough, cheers. I suppose for the Peugeot a prototype is one thing, when they got nearer to production they might want to rethink - perhaps GM is doing the same thing, and trying to 'think out of the box'
        On the numbers you have given it sounds insane though.
        • 4 Years Ago
        Yeah..... *carbon fiber*.
      harlanx6
      • 4 Years Ago
      Here is a site I ran into with a wealth of information on Wankel developement.
      http://www.rotaryeng.net
        harlanx6
        • 4 Years Ago
        @harlanx6
        That's the key point. Obviously you can get huge energy from a small package, but why aren't they more fuel efficient? As a range extender, because of it's small size, it could be useful, especially in a vehicle that is mainly an EV, with the Wankel as a backup. As recharge stations proliferate, the Wankel might just be a good solution for when we "run out of battery" so to speak. A small TD is an attractive alternative also.
        • 4 Years Ago
        @harlanx6
        Interesting stuff! i see how a rotary motor could be a *dream* for an aircraft. However i can't find any valid arguments on why the fuel economy is so bad, and what can be done to increase it. Also, you'd think the extra weight of all the fuel you have to carry would negate some of the weight savings.

        But holding the motor between your hands is pretty freaking cool. You could do that with a 1.0L 3 cylinder block, but it just doesn't compare..

        You'd think that if it could be a more efficient motor, Mazda would have had success with it already. Since the 70's, their rotary-powered cars have had problems with fuel economy. The modern one drinks fuel like a v8.. not good.
        • 4 Years Ago
        @harlanx6
        'Despite its many advantages in the areas of power to weight ratio, freedom from vibration, and some others, the Wankel engine suffers from two mayor problems: Sealing, and fuel efficiency.

        The problem of properly sealing a Wankel engine's moving parts is a tough one. While piston engines use multiple springy steel rings for sealing their round pistons against the round cylinders, and get reasonably good results from this simple and age-old technology, the problem is much harder in the Wankel. There are long, flat edges to be sealed. The corners formed by the apex seals and the rotor-to-wall seals are particularly hard to get airtight. And bad sealing not only makes an engine loose power, and burn more fuel, but it also causes lots of additional pollution - something that is unacceptable in today's world.

        Fortunately the technology has brought great advances in this field. In the 1950s it was still very common that the Wankel cars failed because of broken seals, but nowadays some companies specializing in sealing have demonstrated Wankel engines that run almost forever without such breakdowns. So today it all boils down to Wankel seals being more costly than piston rings, but they are approaching the same level of reliability and effectiveness.

        Another matter is fuel efficiency. If you take a certain amount of fuel, and burn it, you get a certain amount of energy, which can be removed from the burned mass as heat, or as mechanical power through expansion. In a real engine, both things happen, and the ratio between the two defines the fuel efficiency. In the interest of good efficiency, as much energy as possible should be removed by expansion. So it is in the interest of fuel efficiency that the combustion chamber be as closely spherical as possible, thus minimizing the conductive surfaces for a certain amount of enclosed volume. This ideal is approached reasonably well by the piston engine with properly shaped pistons tops and cylinder heads, but the Wankel is very far from this! Its long, thin combustion chamber, having lots of surface, really sucks the heat out of the working gases, producing severe losses. The Wankel is inherently inferior to the piston engine in fuel efficiency matters, because of this fact.

        The only way a Wankel could approach a piston engine in efficiency would be by using materials that either are thermally nonconductive (impossible for now), or by operating the entire engine at such a temperature that little heat is extracted from the gases. We do have metals now that can work hot enough, but we do not have proper lubricants. All present-day engines are temperature-limited by the available lubricants. And when higher-temperature lubricants become available, they will first benefit piston engines, since these expose no sliding surfaces to the gases at the moment of highest compression, while Wankel engines do. Wankels would need much better lubricants than piston engines, to improve efficiency by the path of running hotter.

        For the time being, the Wankel is a novelty, that can be rightfully applied in places where its specific advantages outweigh its disadvantages, but the great mass of internal combustion engines will keep employing pistons. And I will keep looking for a nice plane that deserves being powered by my Wankel! '

        http://ludens.cl/aeromod/wankel/wankel.html
      • 4 Years Ago
      Over at Edmund's they say that they had an audience with the GM people, so presumably it is semi-official.
      It sounds as though it must be about right, if they hope to sell any against the Leaf.
      • 4 Years Ago
      Finally, someone thought of using an economical engine!

      • 4 Years Ago
      How about Government Motors focus on building a FIRST generation Volt.
        • 4 Years Ago
        Of course they're working on the 2nd gen vehicle before the 1st gen vehicle goes into full production. Anything else would be irresponsible.

        Failing to plan for the future is planning for failure.
      harlanx6
      • 4 Years Ago
      The competition is forcing rapid development of better alternatives. A TD or rotary engine makes more sense than a standard 4 cylinder gas engine anyhow. There have been some recent developments in rotary technology also. Rotarys have great potential, and are overcoming some of their quirky problems.
        • 4 Years Ago
        @harlanx6
        I hope so. They're (rotaries) aren't known for fuel efficiency or longevity.
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