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2G Compression Numbers

Posted by cornboy, Jul 5, 2020

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  1. cornboy

    cornboy Probationary Member

    28
    3
    Joined Feb 28, 2020
    Manhattan, Kansas
    Hey I'm sorry if this is a bit redundant but I wanted to get y'all's input on my eclipse.

    Trying to decide if I should have it rebuilt or not, ran a compression test (though it was cold) and got 185/170/180/160, apparently it's a 2.1 stroker with a 9:1 compression ratio.

    Is that 160psi something I should be worried about, or within tolerances for the compression, I know the general rule of thumb is 14psi of variance.

    Thanks
     

    Street Build 192  3

    1996 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  2. silvreclips

    silvreclips Proven Member

    1,277
    332
    Joined Jul 19, 2005
    Greenville, South Carolina
    You need to run the compression test when the motor is hot. If that cylinder is still lower than the others. You can add a tiny amount of oil to the cylinder to see if the numbers go up. That would indicate worn rings. It's not something I would be overly concerned with. I do a compression check once a year and compare those numbers with previous years to give me some idea on how motor is doing.
     

    Autocross Build 595  1

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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    camocorvette and TK's9d2TSi like this.
  3. cornboy

    cornboy Probationary Member

    28
    3
    Joined Feb 28, 2020
    Manhattan, Kansas
    Fair, I just bought the car a few months ago and am in the middle of replacing the entire cooling system, so I can't exactly run the engine till it gets warm, but I'll definitely run it again once I get a new radiator and hoses.
     

    Street Build 192  3

    1996 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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    camocorvette likes this.
  4. jkuga

    jkuga Proven Member

    117
    17
    Joined Feb 12, 2017
    Silverton, Oregon
    I'm not as experienced as most on here, but I did an compression test on my engine without it fulled heated up and got about the same results as you with one cylinder a lower. A while after I did a leak down test with the engine hot and lost virtually no pressure in all cylinders. Just sharing my personal experience here.
     

    Street Build 496  8

    1999 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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    camocorvette likes this.
  5. cornboy

    cornboy Probationary Member

    28
    3
    Joined Feb 28, 2020
    Manhattan, Kansas
    Thanks man, I think I'll go ahead and do all the important maintenance stuff first and just keep using the block without rebuilding it. I'm not planning to make much more than 350 crank horsepower so it should be somewhat reasonable.
     

    Street Build 192  3

    1996 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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    jkuga likes this.
  6. Jk's97DSM

    Jk's97DSM Proven Member

    171
    34
    Joined Apr 27, 2006
    Norfolk, Virginia
    A 10-15 psi difference is a reason for concern.
     

    163  1

    1990 Mitsubishi Mirage EXE (SLO CSM)
    manual · Misc Vehicles

    Street Build 484  1

    1992 Eagle Talon TSi AWD
    awd · automatic · 1G DSM
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  7. cornboy

    cornboy Probationary Member

    28
    3
    Joined Feb 28, 2020
    Manhattan, Kansas
    Should I pull the engine and get it rebuilt?
     

    Street Build 192  3

    1996 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
    Loading...
  8. cornboy

    cornboy Probationary Member

    28
    3
    Joined Feb 28, 2020
    Manhattan, Kansas
    I'm not trying to make massive numbers, in fact right now I just want to get the car driving without weird issues. But if a 10psi difference is enough that like 7 pounds of boost is gonna f*** it up, I'll definitely take it to a shop.
     

    Street Build 192  3

    1996 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  9. silvreclips

    silvreclips Proven Member

    1,277
    332
    Joined Jul 19, 2005
    Greenville, South Carolina
    No, it will be fine. I would not be concerned one bit.
     

    Autocross Build 595  1

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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