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
    669
    Thanks
    85
    Thanked 458 Times in 251 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
    4,762
    Thanks
    2,662
    Thanked 1,574 Times in 913 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: 46.5 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.8 mpg (Imp)


  3. #3
    Senior Member ahausheer's Avatar
    Join Date
    Dec 2015
    Location
    Mission Viejo
    Country
    United States
    Posts
    303
    Thanks
    152
    Thanked 106 Times in 67 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
    2,228
    Thanks
    815
    Thanked 1,217 Times in 741 Posts
    You might email Mitsubishi?

  5. #5
    Senior Member
    Join Date
    Nov 2017
    Location
    Squamish
    Country
    Canada
    Posts
    328
    Thanks
    1
    Thanked 121 Times in 77 Posts
    11.5:1, as listed on this forum in about 7 different places.Name:  Screenshot_20190909-204142_Drive.jpg
Views: 221
Size:  88.4 KB

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage ES 1.2 manual: 43.1 mpg (US) ... 18.3 km/L ... 5.5 L/100 km ... 51.7 mpg (Imp)


  6. #6
    Senior Member
    Join Date
    May 2014
    Location
    Country is Europe, state is Germany
    Country
    Germany
    Posts
    669
    Thanks
    85
    Thanked 458 Times in 251 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
    Senior Member Fummins's Avatar
    Join Date
    Oct 2016
    Location
    In a box
    Country
    North Korea
    Posts
    2,331
    Thanks
    935
    Thanked 1,162 Times in 744 Posts
    Say it don't spray it

    Is your topend all carboned up again?
    Truck
    POS Nissan
    Optima

  8. #8
    Senior Member
    Join Date
    May 2014
    Location
    Country is Europe, state is Germany
    Country
    Germany
    Posts
    669
    Thanks
    85
    Thanked 458 Times in 251 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
    328
    Thanks
    1
    Thanked 121 Times in 77 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: 43.1 mpg (US) ... 18.3 km/L ... 5.5 L/100 km ... 51.7 mpg (Imp)


  10. #10
    Senior Member
    Join Date
    Nov 2017
    Location
    Squamish
    Country
    Canada
    Posts
    328
    Thanks
    1
    Thanked 121 Times in 77 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: 43.1 mpg (US) ... 18.3 km/L ... 5.5 L/100 km ... 51.7 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
  •