I have 2 cars (Prius C and Honda Fit) with 1.5L and diff HP. Why?

Discussion in 'Prius c Main Forum' started by rosethornil, Aug 5, 2022.

  1. rosethornil

    rosethornil Member

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    Just a technical question.

    According to the specs, the 1.5 liter engine in my 2016 Prius C generates 66 HP (ICE) and 33 HP (MG1 and MG2). But the 1.5 liter engine produces 66 HP. Is this right?

    My 2019 Honda Fit (recently acquired) has a 1.5 liter engine and it generates 128 HP.

    What's the difference? Both cars are surprisingly similar in size and weight, but the Honda Fit feels like a race car compared to the Prius C.

    Thank you (in advance) for explaining this to me.

    Rose
     
  2. Mendel Leisk

    Mendel Leisk Underfoot

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    Apart from the horsepower differences, Honda's tend to have "touchy" gas pedal. Harder to modulate for a smooth getaway. Makes it feel peppier.
     
  3. rosethornil

    rosethornil Member

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    I don’t think this is an issue of throttle sensitivity. I pretty much floor the Prius C out from every stoplight, and yet the Honda Fit is far zippier.

    Both engines are 1.5 L, and both cars are about the same size. It’s a real head scratcher.
     
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  4. ChapmanF

    ChapmanF Senior Member

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    Your Honda has a 1.5 L Otto cycle engine designed to produce a higher peak power.

    Your c has a 1.5 L Atkinson cycle engine designed for extreme efficiency. The Atkinson cycle delivers lower peak power, which is ok, because you have the hybrid powertrain to supplement it during those brief moments when you need the power to be higher.

    This is the basic key to the Prius powertrain design, all the way back to the first generations.
     
  5. ColoradoBoo

    ColoradoBoo Active Member

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    From what I understand on the complex Prius powertrain, Prius Hybrid's "thrust" is from the electric motor....so when you floor it, the engine does rev up but what it's providing is extra voltage for the electric motor (the ICE runs the MG1 and our traction battery runs the MG2). This is why when you are coasting, and the ICE turns off, you can't notice it...has no impact on the electric motor's operation.
    I've often wondered if the only difference in a regular Prius and the Prime are larger traction batteries or is the electric motor also different? Does anyone know?
     
  6. ChapmanF

    ChapmanF Senior Member

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    Prime has larger traction battery, and also a sprag clutch between the engine block and flywheel, preventing the engine from turning backwards. That allows the motors in the drive train to be used under more conditions, by pushing off against the engine crankshaft, in a way that would spin a normal Prius crankshaft, without that clutch, backward.

    Prime forum has lots of info on that.
     
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  7. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The Honda's Otto cycle engine has an identical expansion and compression ratio, 11.5:1 so the hotter exhaust is still expanding as it exits via the exhaust manifold.

    The Toyota's Atkinson cycle engine lowers the compression ratio 8:1 compared to its expansion ratio 13:1, so it gulps in less air and fuel, but burns it all inside the cylinder. Less power, more efficiency.


    seems to explain it it great detail.
     
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  8. Isaac Zachary

    Isaac Zachary Active Member

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    • Acceleration = Force ÷ Mass. The more mass the car has the less it will accelerate with the same force (or power).
    • Intake and exhaust charges. The displacement is the same, but that doesn't mean the actual amount of air and fuel getting into the engine is the same.
      • Valve size and lift (how far they are pushed in) affect how much air and fuel can get in.
      • Valve duration and timing will dictate at what RPMs the engine will take in air and fuel.
        • At high engine speeds the cylinder isn't filled at bottom dead center as the piston just shot down there before enough air could get in through the valves. Letting the valves stay open longer gives the air more time to make its way in.
        • Conversely, at lower RPMs a valve that's open very long lets some air and fuel get pushed back out before ignition.
        • The same goes for exhaust valves. Also note that letting the exhaust valves open early can let exhaust start escaping and help get more useless exhaust out of the cylinders so you can fill them with more air and fuel. Lots of exhaust in the cylinders will hurt power.
        • One of the main differences between a Toyota hybrid engine and nearly all others is the Toyota uses an Atkinson cycle valve timing that on purposely pushes air and fuel from the cylinders before the ignition cycle.
      • Intake and exhaust geometry design will affect power too since the air/fuel mix and exhaust don't flow continuously, but start and stop. This causes harmonic sound waves to shoot up and down the manifold runners. A sound wave going the right way at the right time can push more air and fuel into a cylinder or pull more exhaust out than what would happen without intake and exhaust runners.
        • Long narrow runners will push or pull more at low RPMs.
        • Short fat runners will push or pull at higher RPMs
    • Different engines can have different rev limits too. The higher you can rev an engine the more cycles you get and the more fuel you can burn creating more power.
    • Combustion chamber design also affects power. And not just the combustion chamber, but how the intake atomizes or de-atomizes fuel. A perfect combustion chamber would be a perfect sphere with the fuel and air perfectly mixed in it.
      • The reality of combustion chambers is that they are never a perfect sphere. Longer distances means the flame has farther to go meaning you get more backpressure as the timing must be advanced, and you get less downward pressure as the flame chases the piston.
      • The other reality is that the mix is never 100% perfect. You always have lean spots and rich spots. Lean spots can spontaneously detonate creating both worse fuel mileage as well as damage to the engine.
    • These and many other factors determine the dynamic (not just static) compression ratio, which affects the thermodynamic efficiency of the engine. More efficiency means you can get more power from the same fuel.
      • This efficiency changes with load and RPMs, so one engine may be able to make more power out of the same amount of fuel at certain RPMs and another at different RPMs making one better for low RPM fuel sipping and the other for high speed racing.
    • Direct injection can increase power because now you only need to get air into the cylinder, and not air plus both liquid and evaporated fuel. The evaporated fuel displaces the air meaning you get less air and fuel than in a direct injection engine. I do believe your Honda may have DI and your Toyota may not.
    • Forced induction of course will also increase power on an engine with the same displacement.
     
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  9. rosethornil

    rosethornil Member

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    Jimbo, that real-life graphic of the two engines (side-by-side) at 3:11 was fantastic. That helps me understand it so much better.

    Thank you for sharing that video! That's just what I wanted to see (and understand).
     
  10. rosethornil

    rosethornil Member

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    Thank you! Yes, my 2019 Honda has DI which my buddy Scotty Kilmer doesn't seem to like. :D

    The explanation below, coupled with Jimbo's video, has helped me understand and is a great blessing.

    Thank you so much for posting this. I am a big fan of understanding how and why of mechanical things.

    When I bought this Prius C (used, with 22,000 miles on it), I had negotiated a really good deal on it, and then the idiot salesman tried to screw me over on something, and I told him, "Do you think it's fun to lie to widows when it comes to selling used cars? Get your general manager out here."

    I then explained that I was going to walk away from the deal unless they took off another $1,000 from the price because LYING is a really bad idea. The problem was this: The A/C compressor had a funny little noise and I asked them to inspect the compressor before I accepted the vehicle. The salesman told me, "We tightened the belt on the compressor. It's fine now."

    I said, "Oh, you tightened the belt and that stopped the noise?" The salesman repeated himself and said, "Yes."

    That's when I said, "Get the general manager out here."

    When I told him that the Prius C had an ELECTRIC compressor and thus had no belts, the salesman's face went pale. The service manager came out and apologized profusely.

    Before that, I had negotiated the price to $13,200 for a 2016 Prius C (in 2018). After I explained that they had lied to the WRONG WIDOW, they gave me my extra $1,000 off the price.

    It was great. LOL.




     
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  11. farmecologist

    farmecologist Senior Member

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    Haha...it is always GREAT to catch the stealerships lying. (y) Unfortunate that it happens at all though.

    Dang...that was a great price for your Prius C. Unbelievable what they are priced at now.
     
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