need to fig comp ratio

Discussion in 'PSI Superchargers Tech Questions' started by jerry hunt, Jan 1, 2010.

  1. jerry hunt

    jerry hunt New Member

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    need to fig rod length

    Total pour is 93.8 4.310 bore 4.500 stroke rod is 7.126 need to get around 10.7:1 with .081 head gasket, We are coming up with a 7.076 rod length can any one verify thanks Jerry Hunt
     
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    Last edited: Jan 1, 2010
  2. Mike Canter

    Mike Canter Top Dragster
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    Jerry the calculator I used gets 11.57:1

    Go http://www.csgnetwork.com/compcalc.html

    Then use a Dome Volume of zero cc and then adjust the amount deck clearance until the Combustion Chamber Volume equals your 93.8 cc pour. I used -.0476" (minus number) and I also stated that your gasket bore was .000" larger than your cylinder bore at 4.310 because you have actual pour measurements.

    You have to scroll down for the final CR answer

    Something I have found that makes it more accurate. For sealing the rings I use light grease or vaseline and I first fill a plastic coke bottle cap with it and level it off with a straight tool like a knife or ruler. The I drop the piston down the hole a few inches then scoop out some of that grease to coat the cylinder wall just below were the rings will sit then I bring up the piston. Now I use the burette to measure how much fluid is needed to make fill that Coke bottle cap back up level to the top. I then add that amount to the total "pour volume" and that is the "true volume".
     
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  3. Tom Jones

    Tom Jones Member

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    Compression ratio

    My calculations say you need 111cc pour volume for 10.7 c.r.
    You have 94 cc, so you need 17cc more.
    That means you need .070 shorter rod, or .070 more gasket, or some combination of thicker gasket plus shorter rod to equal .070.

    Tom Jones
     
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  4. nitrohawk

    nitrohawk New Member

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    make you an adjustible length rod. Adjust until the top of piston volume at tdc divided into total volume at bdc using desired head gsk gives you the comp you want then measure the rod length.
     
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  5. ibaddlizzard@aol.com

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    jerry you get the screw blower if so that comp is a little high. we run our down like 9.8 to 1 and need to lower that for over 96% DOC:cool:
     
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