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Engine exhaust

  1. Jan 28, 2014 #1
    what will be the temperature and pressure at the exhaust of IC engine?
     
  2. jcsd
  3. Jan 28, 2014 #2
    is navier stokes equation is compulsory while solving a problem in CFD?
     
  4. Feb 1, 2014 #3
    On a typical engine with a catalytic convertor the temperature of the piston typically reaches 600* while the gasses or flame temperatures reach temperatures of 2300* to 2500* in the cylinder under compression, once the gasses are no longer compressed the temperatures fall. The pressure in the exhaust is typically 0-2.5 PSI depending on amount of air entering the cylinder or speed of the air, a gauge hooked up before the catalyst will typically read 0 PSI until you snap open the throttle and then have a momentary spike of 1-2 PSI and then come back down to 0-1 PSI while you maintain RPM. While I haven't directly measured the temperature of the exhaust gasses I do know the catalyst temperature measured with an infrared temperature gun is about 300* going in and should be about 50* hotter coming out.
     
  5. Feb 2, 2014 #4

    Ranger Mike

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    a typical compression test on a good IC engine cylinder will read 125 to 180 PSI..a burn exhaust valve will yield 25 to 50 PSI and performance will be notably off. 1 to 2 psi is fictional. maybe on intake side but you can not read it on exhaust side and why would you???
     
  6. Feb 2, 2014 #5

    cjl

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    Ranger: you're talking about cylinder pressure, while geegee is talking about exhaust system pressure. The two will be dramatically different. As for why you would read exhaust pressure? Exhaust pressure will tell you how restrictive the exhaust system is - a significant pressure in the exhaust above ambient indicates that the exhaust is constricting the flow, and that there are potential performance and efficiency gains to be had by changing the exhaust.
     
  7. Feb 3, 2014 #6

    Ranger Mike

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    cj
    having been out of the look on t his one..where are the two gages located to measure exhaust system pressure. where does the exhaust system get its pressure? ultimately you want to know flow restriction of the ex system Right? curious about methodology here..always willing to learn..thanks
     
  8. Feb 3, 2014 #7
    Both of these are going to very dependent on where in the exhaust system you measure them, and how much power (exhaust gas) the engine produces (is producing) v's exhaust pipe size and muffler restriction. At WOT a typical engine and exhaust system (on a road car) will generate upto 5psi over atmospheric pressure at full power in the exhaust manifold, with the temp ranging from 500-600deg c. Turbocharged engines will be higher. This is why fitting a better flowing exhaust system allows the engine to breathe more efficiently, making more power, and using less fuel overall.


    Damo
     
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