• Apr 24th 2011 at 8:21AM
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In early April, at the SAE 2011 High Efficiency IC Engines Symposium in Detroit, MI, Toyota's Koichi Nakata declared that the Japanese automaker is exploring ways to further reduce the fuel consumption of its upcoming hybrid models. According to Nakata, Toyota aims to develop a gasoline engine that operates at more than 45 percent thermal efficiency for use in future hybrid vehicles.

To put that number into perspective, the engine in the first- and second-generation Toyota Prius had a thermal efficiency of approximately 37 percent and the 1.8-liter mill in the third-gen Prius boasts a thermal efficiency of 38 percent.

Toyota is focusing on two concepts to reach its thermal efficiency goal. Concept 1 is a cooled EGR stoichiometric spark-ignited direct-injection engine that features a long stroke design. The long-stroke setup, according to Toyota, reduces heat loss, increases piston speed and creates more chamber turbulence, which improves combustion. Concept 2 is a turbocharged, lean-burning engine that incorporates the same basic design of Concept 1.

So far, Nakata claims that the engine development team has achieved a 42.4 percent thermal efficiency with Concept 1 and 43.7 percent thermal efficiency using the turbocharged, lean-burning Concept 2 design. Does this mean that a turbo'd Prius may be coming soon?


2011 Toyota Prius
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    • 1 Second Ago
  • 20 Comments
      Arun Murali
      • 4 Years Ago
      Should give you about 10% increase in real world.
      tantareanujellob
      • 4 Years Ago
      I was hoping they would go for a carbed V8 for the next one. What a waste.
      Rotation
      • 4 Years Ago
      What does thermal efficiency mean here? If they add a system that uses energy but produces energy at the output shaft, it would show up as increased thermal efficiency even though more gas is used to go the same distance. A good example of this is multivalve or OHC engines. They produce more output but also use more input energy to run the more complex valvetrain. The real question is how much energy is used to propel a certain distance. If this really goes up 20% that would be amazing. Go for it, Toyota!
      2 Wheeled Menace
      • 4 Years Ago
      Wow, multi week stale old news from GCC.. Oh well, i'll bite. This is awesome. Too bad the torque is reduced very badly in atkinson engines; it would be nice to see something like this is in a non-hybrid that the majority can afford. Big kudos to Toyota for making it happen.
        dellrio
        • 4 Years Ago
        @2 Wheeled Menace
        The average price of cars sold in the United States last year was $32,000. The average price of a Prius sold last year was $28,000. The Civic hybrid, and the fusion hybrid among others also fall in below the $32K Price. It seems that the majority of new car buyers have hybrid options in range.
      EVdriver
      • 4 Years Ago
      This (old news btw) should have been deserved a breaking qualifier. 4. generation Prius will be even more tremendous to than I thought. With this ICE component alone, 60+ EPA MPG is easily achievable. Improved battery, control electronics and electric motors could raise this by another 5-10 MPG. Welcome to the world of 70+ non-plugin Prii.
      Peter
      • 4 Years Ago
      The Prius remains in a class of one so I suspect this will wait to the 2015ish next generation The Camry hybrid is looking a bit tired and needs such attention soon 33 mpg-US (7.1 L/100 km) city / 34 mpg-US highway is fairly ho hum now vs Sonata 24 mpg city/35 vs Sonata Hybrid 37/39 vs Fusion Hybrid 41/36 vs Altima Hybrid 42/40
        Peter
        • 4 Years Ago
        @Peter
        Altima Hybrid 35/33
        Ziv
        • 4 Years Ago
        @Peter
        EPA gives the Altima hybrid a solid 33/33, not 42/40. http://www.fueleconomy.gov/feg/findacar.htm
      Matt
      • 4 Years Ago
      Every car deserves a turbo... even Priora.
      • 2 Years Ago
      A turbocharged gasoline engine with 43.7 percent thermal efficiency, yes, Priuses should be turbocharged. Also Toyota can improve the transmission efficiency. These will result in a nice improvement in fuel efficiency. I would like to see small steam engines to capture waste heat from the exhaust. BMW has a concept called "Turbosteamer" that is able to capture 80 percent of the otherwise wasted energy. That kind of technology improves fuel efficiency on steady and high speeds, that is, on freeways.
      Dan Frederiksen
      • 4 Years Ago
      good. they could also use rocker pistons which have no side wall friction. maybe a two stage engine and even thermoelectric devices. well above 60% should be possible. 2 cylinders might be plenty and make it light. in a light and aerodynamic vehicle it could be down right impressive as a small range extender.
        GeorgeS
        • 4 Years Ago
        @Dan Frederiksen
        Don't know why your post deserved a minus 1 Dan. I erased it. It's always fun to read the comments from the Green Car Congress guys. Here they are along w/ the full article: http://www.greencarcongress.com/2011/04/nakata-20110411.html#comments
        dellrio
        • 4 Years Ago
        @Dan Frederiksen
        +1 as well. Not sure why so much hate?
      Marcopolo
      • 4 Years Ago
      Well done Toyota! I would imagine that this improved technology will find its way into the Lexus hybrid range. Interesting, side note: Rumour of a Plug-in proto-type being tested for the Lexus CT 200 h.
        dellrio
        • 4 Years Ago
        @Marcopolo
        My Prius Lease is up in May 2013. The only car that would keep me from buying a volt at that time would be a Plug-In CT200h priced similarly to or less than the volt. I really like the CT200h
      • 4 Years Ago
      Where the like button?
      Ziv
      • 4 Years Ago
      That would be hella impressive. 38% to 45% would seem to indicate that the Prius MPG would go from 51 to 60+. Anything over 40 is good, over 50 is excellent, over 60 means an 11.9 gallon tank will get you around 700 miles down the road. Hmmm... Maybe a smaller gas tank will be in order... I had thought that Toyota had harvested all the low hanging fruit in the Prius efficiency wars, and that the steady MPG improvements in the future would be smaller. Maybe I was wrong. It would be cool to see Toyota pushing the bar higher.
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