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Gas pressure in internal combustion gasoline engine

  1. Nov 22, 2009 #1
    can anyone please tell me what is the gas pressure which applies on piston head just after combustion in cylinder
    its very urgent and necessary for me to know this
    plz help me
  2. jcsd
  3. Nov 22, 2009 #2

    Ranger Mike

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    cylinder pressure in a 11 to 1 compression ration mills will give you is 12.5 Mpa. ( 1750 psi ifin i did it right converting it) on cheap pump gasoline is about max for todays cars.
    i get about 160 psi per cylinder in the 11:1 comp ration race engine and figure this is without leak down data
    Last edited: Nov 22, 2009
  4. Nov 22, 2009 #3
    OP this is an impossible question to answer in its current form.

    It varies for every engine, and even varies between cycles. You can work out the ideal cycle, but this will be nowhere near what you get in a real combustion chamber. (it's likely to be about 15- 30% higher in the ideal cycle)

    It depends on a huge amount of vairables. The bare minimum you need is. Compression ratio, inlet temperature and pressure and exhaust temperateur and pressure.

    You also need to specify operating conditions, is tis full load, wide open throttle?

    What do you need it for?
    Last edited: Nov 22, 2009
  5. Nov 22, 2009 #4

    Ranger Mike

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    thanks chris
    i agree ..every component will impact on total pressure..i.i. rings, piston, combustion chamber, valves, camshaft profile..intake and exhaust manifolds ...pretty impossible..;.
    the number i threw out should be a pretty average number since is is middle range of variables..good as any to base line..right?
  6. Nov 22, 2009 #5
    Yeah I mean, the Op just hasnt given enough information to even make a stab at an answer. He could be talking about a huge marine diesel for all we know.

    I think you've given just about the best answer possible(average car engine) with the information the op has given.

    Asking whats the pressure in an engine? Is like asking how long is a peice of string.
  7. Nov 23, 2009 #6


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    Do a forum search, I posted some typical values for SI and CI engines on different duties at full load some time ago (peak cylinder pressure, that is).
  8. Nov 24, 2009 #7
    thank you all for replying
    i know i havent given the full discription of problem because i myself don't know the exact things actully i m working on a small project i.e. structural analysis and thermal analysis on slider crank assembly on the engine provided with offset in crank shaft (technology used in kappa engine by hyundai) on 1.2L engine.
    once again thanks for replying
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