Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Results 1 to 19 of 19
  1. #1
    Cadet
    Join Date
    Sep 2006
    Location
    MA
    Posts
    26

    Default volvo compression test

    Does anyone know what a good result is from a compression test on a 1983 Volvo AQ125A?

    I'm planning on testing it this weekend but don't know what range I should be in.

    Thanks

  2. #2
    Seaman Starflight's Avatar
    Join Date
    Sep 2006
    Location
    Boulder City NV
    Posts
    55

    Default Re: volvo compression test

    The book calls for 9.3:1 compression ratio and between 146-174 psi.
    75 Glastron V-179
    AQ130C

  3. #3
    Vice Admiral
    Join Date
    Mar 2005
    Location
    Upstate SC
    Posts
    5,614

    Default Re: volvo compression test

    FWIW 9.3:1 compression = 136 psi
    Just owning a boat does not make you a boater!!

    " Life is so much better on a boat " SS MAYFLOAT

    "All that is necessary for evil to win the world is for good men to do......................nothing" Edmund Burke

    "A simple way to take measure of a country is to look at how many want in, and how many want to get out." Prime Minister Tony Blair

    Page 2,
    Class of '05




  4. #4
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    FWIW...it is more than 136psi.

    You can't calculate the pressure just by the change in volume. You have to take into account energy introduced. This also increases the pressure.
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  5. #5
    Admiral Dunaruna's Avatar
    Join Date
    May 2003
    Location
    Melbourne, Australia
    Posts
    6,015

    Default Re: volvo compression test

    [colour=blue]
    Quote Originally Posted by Limited-Time
    FWIW 9.3:1 compression = 136 psi
    In a perfect world - yes. But there are way to many variables to nail down an exact correlation.

    Rubberduck, taking into account the age, a good result would be around 140-150 with no more than 5% variation.

    Watch this space......................

  6. #6
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    Curious how you think 136 PSI in a perfect world.
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  7. #7
    Admiral Dunaruna's Avatar
    Join Date
    May 2003
    Location
    Melbourne, Australia
    Posts
    6,015

    Default Re: volvo compression test

    [colour=blue]14.7 x 9.3 = 136.71.

    Maybe I should have said 'theoretical' world.
    Watch this space......................

  8. #8
    Vice Admiral
    Join Date
    Mar 2005
    Location
    Upstate SC
    Posts
    5,614

    Default Re: volvo compression test

    Quote Originally Posted by bruceb58
    Curious how you think 136 PSI in a perfect world.
    Atmospheric pressure = 14.695 PSI,(at sea level) 14.7 X 9.3= 136.6 PSI

    Just owning a boat does not make you a boater!!

    " Life is so much better on a boat " SS MAYFLOAT

    "All that is necessary for evil to win the world is for good men to do......................nothing" Edmund Burke

    "A simple way to take measure of a country is to look at how many want in, and how many want to get out." Prime Minister Tony Blair

    Page 2,
    Class of '05




  9. #9
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    Pressure(initial) = Pressure(ATM) + pressure(gauge) = 14.7 PSI. In this case, pressure(gauge) = 0 PSI

    pressure(final) = pressure(ATM) + pressure(gauge) = 136 PSI. Since pressure final = 136, pressure gauge = 136-14.7 = 121.3 PSI.

    Of course the presure final will be way higher that this because the temperature is not constant. By compressing the air, a lot of energy was introduced by the work necessary to compress the air. This causes the temperature to rise drastically and hence causes the pressure to rise.

    This phenomenon is what cause air conditioning to work. Ever feel the output of a compressor? Pretty hot!

    I can see how you guys thought it was 136. You were assuming Ideal Gas Law but forgot about temperature rise and how pressure(gauge) works.
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  10. #10
    Honorary Moderator Emeritus Don S's Avatar
    Join Date
    Aug 2004
    Location
    Western WA.
    Posts
    62,323

    Default Re: volvo compression test

    That's why the dreaded service manual that most people seem to really hate to own, says 146-174 psi.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  11. #11
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    yeah...I bet the Clymer manual says 136.
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  12. #12
    Honorary Moderator Emeritus Don S's Avatar
    Join Date
    Aug 2004
    Location
    Western WA.
    Posts
    62,323

    Default Re: volvo compression test

    More likely it says 631 :devil:
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  13. #13
    Admiral Dunaruna's Avatar
    Join Date
    May 2003
    Location
    Melbourne, Australia
    Posts
    6,015

    Default Re: volvo compression test

    [colour=blue]I didn't say it was 136.

    If you read the posts - we all agree. But it seems we must have a maths lesson from Bruce and a shot across the bow from Don to end the thread.
    Watch this space......................

  14. #14
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    it wasn't a math lesson...it was a thermodynamics/chemistry lesson!

    I just wanted people to realize you cant just multiply the atmospheric pressure times the compression ratio to get the pressure.
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  15. #15
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,383

    Default Re: volvo compression test

    My money is on Don he's rarely wrong no offense guys..........
    Stickly a opinion your milage may vary.

    Speed is how fast you hit the wall
    Torque is how far you move the wall"

  16. #16
    Cadet
    Join Date
    Mar 2010
    Location
    Rock Hill, SC
    Posts
    8

    Default Re: volvo compression test

    WOW!! Put on your gloves and get in the ring. This could be a draw!!

  17. #17
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
    Location
    The Mouth of the Chaumont River, Ny.
    Posts
    52,773

    Default Re: volvo compression test

    it wasn't a math lesson...it was a thermodynamics/chemistry lesson!
    Ayuh,... Good Thing,... 'cause I ain't no Mathamagician.....
    But,...
    I am a Mechanic...

    If I had a 9.3:1 motor showing 136psi,... I'd be comtemplating a Tear-down,+ Rebuild....
    Any Grease is Better,..... Than No Grease at All.......

  18. #18
    Supreme Mariner bruceb58's Avatar
    Join Date
    Mar 2006
    Location
    Peoples Republic of California
    Posts
    18,431

    Default Re: volvo compression test

    Bondo,

    You got bit by the old 4 year old thread again!
    1998 Wellcraft Eclipse 24 Cuddy
    Volvo Penta Duo-Prop 7.4L "LK"

    2006 Sun Tracker Party Barge 21
    Mercury 90 4-Stroke FI
    "Common sense is not very common"
    "Failing to prepare is preparing to fail." -- John Wooden

  19. #19
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
    Location
    The Mouth of the Chaumont River, Ny.
    Posts
    52,773

    Default Re: volvo compression test

    Damn,......

    I thought this was abit Exciting, considering I only left the keyboard long enough to go buy groceries....
    Any Grease is Better,..... Than No Grease at All.......

Similar Threads

  1. 210 PSI Compression Test
    By ajkolar in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 10
    Last Post: April 6th, 2006, 04:01 PM
  2. Help with compression test
    By AtlDawg in forum Johnson & Evinrude Outboards
    Replies: 7
    Last Post: May 11th, 2004, 03:00 AM
  3. Compression test results- updated w/wet test
    By bryandjohnson33 in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 8
    Last Post: July 24th, 2002, 04:05 PM
  4. compression test
    By Meaux in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 1
    Last Post: July 11th, 2002, 06:08 PM
  5. Help with compression test
    By oldboat1 in forum Force & Chrysler Outboards
    Replies: 2
    Last Post: April 6th, 2002, 10:13 AM
  1. iboats Forum Directory - Over 100,000 forum posts organized by topic