Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Compression 3A90, anybody know?

  1. #1
    Senior Member
    Join Date
    May 2014
    Location
    Country is Europe, state is Germany
    Country
    Germany
    Posts
    1,713
    Thanks
    234
    Thanked 1,158 Times in 670 Posts

    Compression 3A90, anybody know?

    Does anybody have the official figures for compression of the 3A90?

    I do have the figures for the 3A92, but they do not apply.



  2. #2
    Administrator Daox's Avatar
    Join Date
    Jan 2013
    Location
    Germantown, WI
    Country
    United States
    Posts
    4,999
    Thanks
    2,892
    Thanked 1,804 Times in 1,017 Posts
    Sadly, we have very little info on the 3A90... I do believe it runs higher compression ratio which would obviously effect your compression testing. Alas, I can't really give you anymore info than that.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


  3. #3
    Senior Member
    Join Date
    Dec 2015
    Country
    United States
    Posts
    360
    Thanks
    194
    Thanked 139 Times in 84 Posts
    Compression ratio is 11.5/1 as stated here https://www.mitsubishi-motors.com/en...S_EnP_3A90.pdf

    I seem to recall that there are regional variations on that engine so I would double check that.

    Can't find the in-cylinder compression pressure anywhere. You might check the owner's manual, sometimes there is a specifications page.

  4. #4
    Senior Member Cobrajet's Avatar
    Join Date
    May 2015
    Location
    Olympia, WA
    Country
    United States
    Posts
    3,126
    Thanks
    1,197
    Thanked 1,848 Times in 1,101 Posts
    You might email Mitsubishi?

  5. #5
    Senior Member
    Join Date
    Nov 2017
    Location
    Squamish
    Country
    Canada
    Posts
    504
    Thanks
    1
    Thanked 181 Times in 116 Posts
    11.5:1, as listed on this forum in about 7 different places.Name:  Screenshot_20190909-204142_Drive.jpg
Views: 896
Size:  88.4 KB

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage ES 1.2 manual: 43.5 mpg (US) ... 18.5 km/L ... 5.4 L/100 km ... 52.2 mpg (Imp)


  6. #6
    Senior Member
    Join Date
    May 2014
    Location
    Country is Europe, state is Germany
    Country
    Germany
    Posts
    1,713
    Thanks
    234
    Thanked 1,158 Times in 670 Posts
    Quote Originally Posted by nickels View Post
    11.5:1, as listed on this forum in about 7 different places.

    Compression was asked, not compression ratio...
    Last edited by foama; 09-10-2019 at 12:39 PM.

  7. #7
    Say it don't spray it

    Is your topend all carboned up again?
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  8. #8
    Senior Member
    Join Date
    May 2014
    Location
    Country is Europe, state is Germany
    Country
    Germany
    Posts
    1,713
    Thanks
    234
    Thanked 1,158 Times in 670 Posts
    Top is perfectly clean inside, like brand new. Zero detectable oil consumption, but only 9bar compression (about 130psi).

  9. #9
    Senior Member
    Join Date
    Nov 2017
    Location
    Squamish
    Country
    Canada
    Posts
    504
    Thanks
    1
    Thanked 181 Times in 116 Posts
    Quote Originally Posted by foama View Post
    Compression was asked, not compression ratio...
    Fine.

    11.5X14.7 is 170psi.

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage ES 1.2 manual: 43.5 mpg (US) ... 18.5 km/L ... 5.4 L/100 km ... 52.2 mpg (Imp)


  10. #10
    Senior Member
    Join Date
    Nov 2017
    Location
    Squamish
    Country
    Canada
    Posts
    504
    Thanks
    1
    Thanked 181 Times in 116 Posts
    If you are about 2500ft above sea level, around 155psi.

    Etc.


        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage ES 1.2 manual: 43.5 mpg (US) ... 18.5 km/L ... 5.4 L/100 km ... 52.2 mpg (Imp)


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •