View Poll Results: Which engine do you think will produce the most power and the best fuel mileage?

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  • I-4

    6 10.91%
  • I-6

    14 25.45%
  • V-6

    4 7.27%
  • V-8

    14 25.45%
  • Box 4

    4 7.27%
  • Box 6

    5 9.09%
  • Don't know

    8 14.55%
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Thread: Engine Power Vs. Engine Displacement Vs. Engine Configuration

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  1. #1
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    Engine Power Vs. Engine Displacement Vs. Engine Configuration

    I have a question about engines. The other thread about turbos and engines inspired me to create this one. If there were six engines- 2.0 L I-4, I-6, V-6, V-8, Box 4, Box 6, all the same size would they all produce the same power or would some engines produce more due to the configuration? I was thinking the V-8 would create the most but then again because they're the same size the cylinders would shrink, thus limiting the amount of fuel used. Would fuel economy be also affected by these different engines?

    Would the same thing happen for diesels as well?
    Last edited by NSXType-R; 07-11-2006 at 12:25 PM.

  2. #2
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    Quote Originally Posted by NSXType-R
    I have a question about engines. The other thread about turbos and engines inspired me to create this one. If there were five engines- 2.0 L I-4, V-6, V-8, Box 4, Box 6, all the same size would they all produce the same power or would some engines produce more due to the configuration? I was thinking the V-8 would create the most but then again because they're the same size the cylinders would shrink, thus limiting the amount of fuel used. Would fuel economy be also affected by these different engines?
    Too many variables. Depends on state of tune(air flow, cams etc), how high they rev ect.

  3. #3
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    You say all of the same size.....I think you should predefine the size and the required power, in order to make a certain vehicle move.
    "I find the whole business of religion profoundly interesting, but it does mystify me that otherwise intelligent people take it seriously." Douglas Adams

  4. #4
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    Like slicks said its way to hard to judge there are too many variables. I think this site will help you out though.
    http://www.autozine.org/technical_sc...ne/smooth1.htm

  5. #5
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    Thanks guys. I was thinking that because they were the same displacement they should create the same power.

  6. #6
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    In my auto technology class in high school my teacher claimed that it was a more effecient design to have a lot of small cyliders than a few very big ones. His reasoning had something to do with the ratio between surface area and volume inside of the cylinders. He used a similar rationalization to explain why a hemispherical head was, in theory, better than a flat cylinder head.

  7. #7
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    But with a lot of small cylinders there would be more surface area which means it would be less thremodynamically effecient wouldn't it?

    Surface area causes heat loss which equates to lost power

    I understand with that reasoning used for Hemi's though. Hemi's are better than flats because hemi's have less surface area than a flat head would. Therefore they are more thermodynamically effecient.

  8. #8
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    Quote Originally Posted by deffenbaugh03
    But with a lot of small cylinders there would be more surface area which means it would be less thremodynamically effecient wouldn't it?

    Surface area causes heat loss which equates to lost power

    I understand with that reasoning used for Hemi's though. Hemi's are better than flats because hemi's have less surface area than a flat head would. Therefore they are more thermodynamically effecient.
    It makes sense what you say about thermodynamic efficiency. I was always confused by his statement because it seemed to me that having more volume in the middle of the cylinder, far away from the walls, would allow a larger percentage of the fuel to be burned. It always confused me because this guy (my teacher) was incredibly knwoledgeable abut cars and I didn't think he would be likely to make a mistake like that. Maybe there is something I'm missing.

  9. #9
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    Alright. Say they theoretically they shared the same parts- injectors, intakes etc. (I know it's not possible since the crankshafts are already different but work with me here ). Would they make the same power each or would their configurations lend some advantage?

  10. #10
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    Quote Originally Posted by deffenbaugh03
    But with a lot of small cylinders there would be more surface area which means it would be less thremodynamically effecient wouldn't it?

    Surface area causes heat loss which equates to lost power

    I understand with that reasoning used for Hemi's though. Hemi's are better than flats because hemi's have less surface area than a flat head would. Therefore they are more thermodynamically effecient.
    yes. this also means more friction loss cuz of having more area, but with smaller pistons you can have a shorter con rods which means higher rpm and thus more power

  11. #11
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    It is easier to fit 4 valves in a flat head, which far outweighs the power gained from a hemi.

  12. #12
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    a 2L V8 will be able to rev much higher than a 2L 4 cylinder becasue the maximum accelration rate of the piston will be far less than the 4 cylinder engine because the piston will not have to travel as far.

  13. #13
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    Quote Originally Posted by h00t_h00t
    It is easier to fit 4 valves in a flat head, which far outweighs the power gained from a hemi.
    I didn't know they had 4 valve per cylinder engines back in the days when flat heads were common. I'll admit though i do not know too much about flat heads. I just thought they had always been 2 valve per cyl.

  14. #14
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    Quote Originally Posted by deffenbaugh03
    I didn't know they had 4 valve per cylinder engines back in the days when flat heads were common. I'll admit though i do not know too much about flat heads. I just thought they had always been 2 valve per cyl.
    I think there is some confusion here, Hootetc was referring to the shape of the combustion chamber which can be hemispheric ar a bit flat. What you are talking about are side valve engine which resulted in flat cylinder heads as there was nothing on top of the cylinders. These type of engines never came with four valves per cylinder as far as I know, but I am always prepared to stand corrected.
    "I find the whole business of religion profoundly interesting, but it does mystify me that otherwise intelligent people take it seriously." Douglas Adams

  15. #15
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    Actually, these goals are contradicting each other.
    The best economy will be achieved with the I-4, whereas the most power will be achieved with the V8.

    Less cylinders mean less friction losses, leading to a better mpg figure.

    More cylinders mean less reciprocating mass, leading to more revving capability.

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