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Featured Wankle range extender

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by bwilson4web, Oct 15, 2017.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Source: Mazda Seems Serious About Turning The Rotary Engine Into A ‘Range Extender’

    We’ve heard this might be a new application of the rotary for a while, but here’s some more concrete news. It won’t be powering a sports car for now, so hold off on your dreams of seeing a new Mazda Cosmo anytime soon. Mazda plans on having an electric vehicle sometime around 2019 with a pure electric model in the Asian and European markets while North America will get the rotary range extender.​

    Small size, light weight, it looks like a good solution to me.

    Bob Wilson
     
    #1 bwilson4web, Oct 15, 2017
    Last edited: Oct 15, 2017
  2. bisco

    bisco cookie crumbler

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    is there any data on why this would be a better generator than any other type of engine?

    what are the consideration, size/weight/fuel usage/emissions/other?
     
    #2 bisco, Oct 15, 2017
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  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    For example, my BMW i3-REx has a two cylinder, ~36hp, modified motorcycle engine. An equivalent sized Wankle should be the size of the motorcycle engine crankcase and lighter. It should also have significantly less vibration since the moving masses have shorter throws:
    Wankel engine - Wikipedia

    The Wankel engine has the advantages of compact design and low weight over the most commonly used internal combustion engine employing reciprocating pistons. These advantages have given rotary engine applications in a variety of vehicles and devices, including: automobiles, motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chainsaws, and auxiliary power units. The point of power to weight has been reached of under one pound weight per horsepower output.[2]​

    In EV operation, the range extender engine and generator are 'dead weight' that reduces range and impacts performance. So having a smaller, lighter engine is good. Higher rpm also allows a much smaller generator, another good thing. When extending the range by charging the battery, the Wankel has a nice, steady power requirement which mitigates some engine weakness in throttle operation. Best of all, Wankel emissions as a range extender are most likely to occur on the highways, away from urban areas and people.

    Bob Wilson
     
    #3 bwilson4web, Oct 15, 2017
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  4. bisco

    bisco cookie crumbler

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    agreed, but there are other considerations, including noise.

    but the overarching question has to be, why has the rotary not become a reasonable success? pistons must have more advantages overall.
     
    #4 bisco, Oct 15, 2017
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  5. Trollbait

    Trollbait It's a D&D thing

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    Piston engines are better for efficiency, emissions, and reliability. The reliability part could simply be due to all the R&D they have received through the decades. The emissions and efficiency will remain better in a 4 cycle piston engine than a Wankel because the rotary's operation is similar to a 2 cycle's; expelling the exhaust gases before reaching what would be the equivalent to the piston fully down.

    The weight and space savings, plus quietness and smoothness, can make up for the rotary's short comings in efficiency and emissions in a PHEV. Remember, the more time the owner drives in EV, the less time the ICE is running. Which can lead to less gasoline use overall. It's the same math problem used for comparing the Volt to the PiP/Prime. The Volt uses more gas when in hybrid mode, but will spend less time in that mode than the Prius. Depending on the actual pattern of use and charging, the Volt might use less gas in year.

    This wouldn't be the first Wankel as a range extender. Audi had a test fleet of A1 E-trons using one as a range extender. The engine was 254cc, or about twice the displacement of the engine for atypical homeowner walk behind lawnmower.The genset could probably easily sit on top of the lawnmower's deck. It sat in between the rear wheels of the car. Compared to the ICE model, no passenger or cargo space was lost(can't say about the spare), but it was designed as a European city car like the i3 REx; 30 mile EV with 155 miles total.
    [​IMG]
    Green Car Congress: Audi A1 e-tron: Extended Range Electric Vehicle for City Driving

    Originally, the ICE ran at one set speed, but some drivers could still hear it, and found the flat speed unconnected to the car's speed disconcerting. So three set speeds were adopted.
     
    #5 Trollbait, Oct 15, 2017
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