Results 1 to 12 of 12

Thread: Numbers on the side of pistons what do they mean?

  1. #1
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     

    Numbers on the side of pistons what do they mean?

    in ASA the piston number has 3 version,
    STD A
    STD B
    STD C

    i know that with resect to bearings the STD is a standard size with a slight variation.

    so on the side of the piston i would expect to see a corisponding Letter.

    but this is what i have.......

    4 pistons with a 2L
    IMG_20180419_161910_HDR.jpg


    1 piston with a 3L

    IMG_20180419_161904_HDR.jpg


    1 piston with a 5L

    IMG_20180419_161902_HDR.jpg



    do these numbers corrispond to size (diameter) of the piston which should match the the original size of the cylinder bores. However my engine block has 5 bores of size 'C' and one bore of size 'B' so 3 different size of piston would be wrong when i say different diameter i am not talking a 0.5mm or 1.0mm over sized piston which would require a cylinder rebore but a fractional difference within the normal cylinder bore range 81.00mm-81.03mm.
    or
    do these numbers corrispond to weight of the piston which would be selected to match or cancel out some imbalance in the crankshaft.

    i dont know i am just taking a complete guess.


    i can tell you the 6 Pistons with con rods attached were weighed as 6 individual items

    All 2L = 881.5g

    3L = 883.5g

    5L = 883.0g

    so i am not sure what is the correct conclusion to draw.

    What do you guys think?

    i suppose it could just be the casting block identifier the pistons where made in.
    or some kind of batch number, or supplier number, each supplier could have a different number allocated to them.

    straw cluching. lol
    Last edited by Davezj; 03-05-2018 at 12:31 AM.

    Bye for Now!

  2. #2
    paulg23's Avatar

    Offline
     
    Name
    Paul
    Join Date
    Jul 2009
    Last Online
    09-07-2018
    Posts
    389
    Country
    United Kingdom
    Location
    Northampton
    Car
    VR4 - S
     
    These numbers are in the castings so must be pre machining so my guess would be they are the casting tool numbers. As I said, only a guess.
    Too much is just enough.

  3. #3
    elnevio's Avatar

    Offline
     
    Name
    Nev
    Join Date
    Dec 2007
    Last Online
    01-03-2024
    Membership ID
    510
    Posts
    17,953
    Country
    United Kingdom
    Location
    Gloucester
    Car
    VR-4+Panda+shed
    My Garage
    Visit
     
    Do you happen to recall which cylinders each one came out of?
    October 2023 fleet status: 100% operational


    | Legnum VR-4S | Fiat Panda 100HP !! | a blue one! | Avensis T-180 | VR-4 parts van! |

    Why not become a full member of CVR4 and enjoy the additional benefits membership brings?! Information here.

  4. #4
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    Yes I know which cylinder they came from .
    But I have 3 different numbers on the side of the piston and only 2 different cylinder bore sizes according to the stamping on the block. 5 of one size and one of another.


    Sent from my MI 5s using Tapatalk

  5. #5
    Nick Mann's Avatar

    Offline
     
    Name
    Nick
    Join Date
    Sep 2003
    Last Online
    17-03-2024
    Membership ID
    17
    Posts
    24,895
    Country
    United Kingdom
    Location
    Redditch
    Car
    Legnum type-S
    My Garage
    Visit
     
    I would tend to agree with Paul. They can't cast the size tolerance in, it would be measured after machining.

  6. #6

    Offline
     
    Name
    Mike
    Join Date
    Dec 2008
    Last Online
    30-01-2023
    Posts
    57
    Country
    England
    Location
    VIAMOTO
    Car
    FTO GPX/Shogun
     
    Hi

    Each Block is stamped with what size piston the block uses - look at the location on the block

    See https://www.viamoto.co.uk/prodimages...on-diagram.jpg

    But knowing Mitsubishi they probably stamped a 1 2 or 3

    Meaning A= 1, B=2 or C= 3

    Hope that helps
    Kind Regards

    Mike
    ps DO NOT Get confused with the marks for the Big End Shells or Main Bearings - see below
    http://www.viamoto.co.uk/prodimages/...ing-choose.jpg

  7. #7
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    Thanks for the info it is correct, but not what I am asking about that.

    I know how to size the pitons for the engine block and how to size the bearings for the crank and con rods.

    It was the numbers cast into the side of the pitons that I was curious about.
    It has been suggested that it is a casting block number. Which is logical but it is strange that the 3L and 5L pitons are heavier than the 2L pistons. So maybe it is just a casting block with slightly different dimensions.



    Sent from my MI 5s using Tapatalk

  8. #8
    swinks's Avatar

    Offline
     
    Name
    Tomasz
    Join Date
    Feb 2008
    Last Online
    21-10-2022
    Posts
    4,578
    Country
    United Kingdom
    Location
    Bourne, Lincs.
    Car
    ex-Galant VR4
     
    Isn't it related to weight and counter balance of crankshaft? Middle piston heavier than two outer one? Just thinking...
    Ex: Galant VR4
    Running 268 HP ATW and 443 Nm torque at 0.9 bar
    Now: Lancer Evolution 8 FQ-300
    Running 325 HP ATW and 510 Nm torque at 1.6 bar

  9. #9
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    Quote Originally Posted by swinks View Post
    Isn't it related to weight and counter balance of crankshaft? Middle piston heavier than two outer one? Just thinking...
    I originally thought it was something to do with weight and balancing the rotating assembly.
    But I don't think car manufactures have the time or the inclination to balance the whole rotating assembly. Just the individual parts to a basic level. Just the crank I think really.

    Sent from my MI 5s using Tapatalk

  10. #10
    swinks's Avatar

    Offline
     
    Name
    Tomasz
    Join Date
    Feb 2008
    Last Online
    21-10-2022
    Posts
    4,578
    Country
    United Kingdom
    Location
    Bourne, Lincs.
    Car
    ex-Galant VR4
     
    I rather think that each crankshaft assembly is individually balanced, same principle as for turbocharger build, and custom engine build.

  11. #11
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    Quote Originally Posted by swinks View Post
    I rather think that each crankshaft assembly is individually balanced, same principle as for turbocharger build, and custom engine build.
    It is an odd thing.
    I have not been able to find out any diffinitive information from anywhere.
    I might just send the pictures of the pistons to the colt car company (mitsubishi UK) to see if they can shed some light on the subject.


    Sent from my MI 5s using Tapatalk

  12. #12

    Offline
     
    Name
    nigel
    Join Date
    Nov 2010
    Last Online
    23-12-2021
    Posts
    2,192
    Country
    United Kingdom
    Location
    moira
    Car
    black l200
     
    it cpould be manifactures code for casting as i dont think mits would be casting them

Similar Threads

  1. WTB: Vr4 pistons
    By dutch driver in forum UK Parts for Sale / Wanted
    Replies: 6
    Last Post: 21-02-2016, 10:44 PM
  2. Forged pistons?
    By Gly in forum Engine
    Replies: 54
    Last Post: 31-10-2012, 12:52 AM
  3. i need help with the pistons
    By wilmar88 in forum Engine
    Replies: 4
    Last Post: 06-10-2011, 11:52 AM
  4. FOrged Pistons.....
    By triniVr4 in forum Engine
    Replies: 1
    Last Post: 13-09-2006, 08:18 AM
  5. Pistons?
    By TTV6VR4 in forum General / Questions
    Replies: 1
    Last Post: 16-08-2005, 07:58 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
  •