• May 26, 2010
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 and 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.

Photos Copyright ©2009 Sam Abuelsamid / Weblogs, Inc.

[Source: Inside Line, General Motors]

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    • 1 Second Ago
      • 4 Years Ago
      The first gen is not on sale yet.
      • 4 Years Ago
      The generator needs to have enough power to sustain the highest legal roadway speed in USA (80mph) continuously, and for a powertrain with a worldwide market, it has to maintain the highest legal roadway speed in the worldwide market continuously, and that's in the 140 - 150 km/h range (about 90 mph). And it has to do that against some reasonable headwind and with a full load. The batteries will take care of short-term power demands above that. But, all that suggests that 15 - 18 kW is not enough. 40 or 50 kW (65-ish horsepower for the Americans) is probably more like it. A 1.4 litre gasoline engine tuned for economy (Atkinson cycle, which has the side effect of reducing maximum power output when running in Atkinson mode) is likely not all that far off based on this criteria ... and it was "available" and could easily meet emission requirements (not necessarily true of diesels or Wankel rotaries).

      If they do more development to get HCCI or diesel operation to get the range extender more efficient (but still have enough power available) that's great.

      The main problem ... is the small production volume. I have a customer who is going to be building parts for those cars, and the production forecast for the first year is remarkably small. There ain't going to be many of those cars around.

      Maybe it's time to invest in one as a future low-production classic car ...
      • 4 Years Ago
      GM would be stupid to go with a Wankel rotary. Rotaries are known for being bad on gas and not as reliable as a piston engine. Most Americans think GM products are inefficient and unreliable as it is. Why would you want to combine GM's poor reputation in reliability and gas mileage with Wankel's poor image in reliability and gas mileage, on the one GM product that is supposed to represent the new, reliable, capable, fuel-efficient GM?

      GM is already pushing the tech curve with the Volt. The Volt is easily going to be the most technologically advanced and complex vehicle on the market today, which means lots of parts that can break down in real-world situations regardless of make. GM should be sticking to proven tech that it knows how to make in as much of the Volt as humanly possible. The worst possible outcome would be using technology that is proven unreliable, and turn GM's most important automobile into the next Vega.
      • 4 Years Ago
      Hah.. well let's focus on getting the first model right, eh? :)

      GM's been researching HCCI for a long time now. Maybe this 2 cylinder engine could implement this, getting diesel MPG out of gasoline, with none of the size / weight / soot of a diesel engine. It seems like the best solution, even versus a rotary motor.

      As it stands right now, their MPG goal for the range extender is 50mpg, which is not shabby at all.

      70+mpg should be possible though. The 1.4L i4 is pretty primitive actually... being the same block that powers the Chevy Cruze, probably with some little tweaks here and there.
      • 4 Years Ago
      Let's just get THIS one out first, then we'll talk about the next one...
      • 4 Years Ago
      wankle ev range extender ehh... cool, doo it, im tired of fiat and audi and everyone else showing off concepts with said combo with no desire to build it, given how the volt came into being, i have zero doubts GM can go from no to a production wankle in no time, easy peasy.
      • 4 Years Ago
      DO THE DIESEL! The electric motors will take care of the slow speeds/acceleration and the diesel will take over during cruising...make it happen!
        • 4 Years Ago
        You do know the Volt is always run on electric right?

        It's not like a Prius where the ICE would actually propel the vehicle. It's just a generator basically.

        That said, the diesel is still a good option, but not necessarily for the reason you are stating.
      • 4 Years Ago
      Given that the challenge for HCCI engines is managing the shift between spark and compression ignition, the constant state load such an engine would face in this sort of application is perfect.

      That said, Wankels and turbines make sense too. The very things that make them poor choices for traditional drivetrains make them ideal for series hybrids. Let's see...a small turbine could be started pretty easily with a 48 or 96 volt motor and then deliver a nice smooth, space & weight efficient power source.
      • 4 Years Ago
      A small diesel would seem to make the most sense. Even the most efficient rotary will not touch a tiny diesel.Fuel cells would be a joke at this point. There are diesel bike versions now that get near or above 100mpg. That would mean 500 miles off-battery with just the 5 gallon tank, making long trips far more enjoyable.

      And gen2 of the Volt packs already are double the charge for the same size, so GM could cut the size (weight and probably cost) in half right there.
        • 4 Years Ago
        The limits to this will be the limits of GM's own engine building capabilities. That is why the Volt is getting an inline 4 Cylinder and a Cruze platform. Any money spent developing another engine is another barrier to making a profit off this car.

        A small diesel would seem to make sense in this application. Unfortunately they tend to add weight which is already an issue for the Volt and GM isn't known for making small diesel engines.
        • 4 Years Ago
        The 100mpg diesel I reference was for a cruiser-style bike (something like 1-1.2L). It made enough hp and torque to easily work as a range extender for a Volt. For that concept cruiser it was a beast, but I cannot find anything on it anymore. Company probably died years ago.
        • 4 Years Ago
        The best option would be a modern two-stroke diesel engine. Much lighter than a 4 stroke and a perfect match to power a generator that runs on a constant rpm. A 500cc engine would produce plenty of power to run the generator. On the contrary a four-stroke diesel would have to be almost twice the size to generate the same power.
        • 4 Years Ago
        I'm still waiting for GM to partner with a motorcycle company like Yamaha or Kawasaki. Their two and four cylinder engines are very compact, inexpensive, and can be easily tuned to operate in a generator fashion.

        The engines are proven, the collaboration would be vastly less expensive than designing a new engine and small size would make packaging a simpler solution.
        • 4 Years Ago
        I don't doubt that such a bike existed or is possible, but even with 100% efficiency at converting from potential to kinetic to electrical, the kw required to move a cruiser 100 miles are vastly different than the kw required to move a volt 100 miles.

        I'm not saying it's not a good idea, just that 100 mpg in range extend mode is foolishly optimistic.
        • 4 Years Ago
        With battery technology constantly evolving, the opportunity to gain range while reducing weight and costs should be the most important factor. As for range extending, I do not see GM having as much expertise with diesels compared to the VW Group. However GM has been hard at work on HCCI engines, which would seem to be the best solution for a new Volt. These engines could operate on various fuels, and are said to be very efficient. The inherent issues with this type of engine should not be a problem as a range extender, since they should only have a narrow and constant operating range.
        • 4 Years Ago
        Agreed. And it could be tuned to run at a constant rpm that produces the greatest efficiency.
      • 4 Years Ago
      They see me rollin'
      They hatin' ....
      • 4 Years Ago
      GM should focus on building and selling a FIRST generation Volt.
      • 4 Years Ago
      Like lipstick on a pig..
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