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CompressionRatio FAQ?


CompressionRatio FAQ?

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    CompressionRatio FAQ?

    Can anyone help me out with compression ratio? I mean, I though it was a function of bore and stroke, but i am obviously naive. what is the deal? are they talking about effective CR due to inefficiencies in the pumping process? I just don't understand how changing your pistons can change the CR. Static CR is still volumeBDC/volumeTDC, by defintion. Generally engine calcs are done with that figure for gas turbine engines. What are they referring to with domed pistons and shit? WhatTheFuck?

    Domed-piston has a dome (By visual)
    Dished-piston has a dish (by visual)

    Not sure about the rest.

    I have another question, will a bumped compression ratio hurt you gas milage?


      never mind, i am just lazy

      i figured it out

      CR1=Vu/Vc where Vu=Volume Uncompressed, Vc=Volume Compressed (undomed pistons)

      CR2=(Vu-D)/(Vc-D) where D=Dome Volume (negative for a dish)

      then you can see a bump in CR2 pretty easily with this example

      For a theoretical engine with
      Vu=50cc and Vc=10cc, CR1=5, and if D=2.5cc, then CR2=(50-2.5)/(10-2.5)

      I got it, sorry, I was just not putting it together in cartoon form correctly/


        gas mileage

        gas mileage is a function of compression ratio, and as CR goes up, so does efficiency of the engine.
        Diesel engines have much higher compression ratios, and higher efficiency in accord with that.
        But, remember. all that extra power you are producing is very likely to be excercised through additional speed, and then you might even push her a time or two on every drive, and then vtec and all, and you will still see economical fuel consumption. these cars just don't waste gas. and the ecu responds to changes like a fucking living thing. it is rediculous. anyway, yes, you will see increased MPG, but you will have more fun and drive faster if all is correct, and gains will be negligible or negative. if you drove slow, you might see a gain. but why bump CR unless you wanna drive fast.