Results 1 to 8 of 8

Thread: Toyota Engine Compression ratios - How they come from factory

  1. #1
    Noooob
    Join Date
    Jun 2010
    Name
    Matt
    State
    NSW
    Location
    Campbelltown
    Country
    Australia
    Posts
    5,207

    Default Toyota Engine Compression ratios - How they come from factory


    TO REMOVE ADS, PLEASE
    REGISTER OR SIGN IN
    Standard Factory Compression Ratios


    4age


    16v Bigport - 9.4:1
    16v Small Port - 10.3:1
    20v Silvertop - 10.5:1
    20v Blacktop - 11:1


    Gze


    Supercharged GZE Bigport - 8:1
    Supercharged GZE Smallport - 8.9:1


    7a


    7afe - 9.5:1
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

  • #2
    Moderator dove grey 64's Avatar
    Join Date
    Aug 2010
    Name
    Geoff
    State
    VIC
    Location
    mt dandenong
    Country
    Australia
    Posts
    2,444

    Default

    was trying to work out what 9.4:1 would convert to in psi readings and found this on google
    There is really no 100% accurate way to calculate your compression ratio from psi, but there is a formula that will get you fairly close. First take your psi reading and divide it by 14.7 (for example, psi reading is 170 divided by 14.7 = 11.56). Then take your engine size and multiply by .01 (for example 250cc x .01 = 2.5). Then add 1 to that number, so then you have 3.5. Last you will take the 11.56 that you got from dividing the psi reading (170psi) by 14.7 and subtract that 3.5 from the 11.56 ( so you have 11.56 - 3.5 = 8.06). And that is your approximate compression ratio (8.06:1). Like I said, there is no formula that will get you an exact reading just because it is virtually impossible, but that formula always gets you fairly close.
    now im picking up my brain off the floor.
    im pretty sure it works out to between 170psi to 199psi, anyone else know?

  • #3
    Noooob
    Join Date
    Jun 2010
    Name
    Matt
    State
    NSW
    Location
    Campbelltown
    Country
    Australia
    Posts
    5,207

    Default

    The actual numbers on the compression test can be influenced by a heap of different things... I've generally learnt that the variance between cyclinders must not be more than a few % otherwise you have a problem.

    Leak down tests are also good, but not fool proof. You can tell allot by using a bore scope if you know what you are looking for.
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

  • #4
    Glenn ke_70's Avatar
    Join Date
    Dec 2008
    Name
    Clay
    State
    SA
    Location
    Barossa!
    Country
    Australia
    Posts
    5,318

    Default

    we adding to these?

  • #5
    Noooob
    Join Date
    Jun 2010
    Name
    Matt
    State
    NSW
    Location
    Campbelltown
    Country
    Australia
    Posts
    5,207

    Default

    yeah why not....
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

  • #6
    Senior Member Skid_KE70's Avatar
    Join Date
    Dec 2008
    Name
    Daimon
    State
    Tasmania
    Location
    Launceston
    Country
    Australia
    Posts
    476

    Default

    it would be interesting to see what compression ratio a silvertop 20v 4age is with smallport 4agze pistons. this seems to be a fairly common conversions for people wanting to go turbo with a low budget. i for one have used this combination and it worked well aside from it then being an "interferance engine"
    ---- Fryin Fifth Represent ----

  • #7
    Noooob
    Join Date
    Jun 2010
    Name
    Matt
    State
    NSW
    Location
    Campbelltown
    Country
    Australia
    Posts
    5,207

    Default

    I saw a comp test result on a 14:1 engine over the weekend and the result was up around 255psi per pot....
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

  • #8
    Veteran lolwat's Avatar
    Join Date
    Oct 2009
    Name
    Michael
    State
    NSW
    Location
    Crimebrook 2749
    Country
    Australia
    Posts
    3,974

    Default


    TO REMOVE ADS, PLEASE
    REGISTER OR SIGN IN
    my old bigport had 235psi across all 4, bigport pistons, head was shaved nothing extreme, TRD 0.8 headgasket

    cam overlap isnt going to help when getting comp readings either


    useing that "formula"from above, it ahs 10.98:1, beleivable, when it says multiply your engine size by 0.01, per cyc not over all
    Last edited by lolwat; 4th December 2012 at 01:25 PM.

  • Similar Threads

    1. 7AG and compression ratios
      By Golden Circle in forum Technical - Questions
      Replies: 21
      Last Post: 28th May 2012, 06:36 PM
    2. Working Out Compression Ratios
      By JJRC in forum Technical - Questions
      Replies: 5
      Last Post: 17th November 2011, 06:22 PM
    3. compression ratios with shaved head
      By dr1ft-pig in forum Technical - Questions
      Replies: 20
      Last Post: 22nd October 2007, 07:42 PM
    4. Compression ratios
      By Jazz9 in forum Technical - Questions
      Replies: 7
      Last Post: 17th September 2007, 01:43 AM

    Posting Permissions

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