1. Welcome to TRD Forums! A community for Toyota, Lexus, and Scion Enthusiasts. To enjoy all the benefits of the site, we invite you to signup.

Engine How to calculate compression drop from dropping compression height?

Discussion in 'Powertrain' started by FriskyDingo, Dec 3, 2014.

  1. Offline

    FriskyDingo Active Member

    Message Count:
    237
    Likes Received:
    42
    Trophy Points:
    38
    Location:
    Canada
    Vehicles:
    2000 Corolla CE
    Anyone know how much the compression would drop on a 1zz if the compression height of the pistons was changed from 1.268" to 1.256"?
  2. Offline

    crolla "Wait did I just lose to a corolla?"

    Message Count:
    496
    Likes Received:
    70
    Trophy Points:
    308
    Location:
    Maryland
    Vehicles:
    ZZE110
    To accurately calculate it, you need some more information.
    1) The bore of the cylinder
    2) The stroke of the cylinder
    3) The volume of the combustion chamber
    4) The compression height of the piston
    5) The dome/dish volume of the piston
    6) The piston-to-deck clearance
    7) The thickness of the headgasket
    8) The bore of the headgasket

    Assuming its a stock 1zzfe **You may want to change some of the values based on what you have, I started filling it out but you can finish it.
    1) 79mm
    2) 91.5mm
    3) The volume of the combustion chamber
    4) 1.256
    5) The dome/dish volume of the piston
    6) The piston-to-deck clearance
    7) 0.5 mm
    8) 79mm

    After you have those, you can plug them into this calculator and it will give you the new compression ratio
    http://www.c-speedr.com/howto/compcalc/compcalc.php
  3. Offline

    FriskyDingo Active Member

    Message Count:
    237
    Likes Received:
    42
    Trophy Points:
    38
    Location:
    Canada
    Vehicles:
    2000 Corolla CE
    Thanks man! I've noticed there's a difference between non-vvti and vvti pistons, also something weird is the 03-08 vibe uses non-vvti pistons.

    Non VVT-I Piston:
    [IMG]

    VVT-I Piston:
    [IMG]
  4. Offline

    FriskyDingo Active Member

    Message Count:
    237
    Likes Received:
    42
    Trophy Points:
    38
    Location:
    Canada
    Vehicles:
    2000 Corolla CE
    I was looking at pistons on ebay and came across this info for both pistons but its listed weird:

    Non VVT-I:
    Compression Ratio:
    0.7874"

    VVT-I:
    Compression Ratio:
    • 0.7885"
  5. Offline

    crolla "Wait did I just lose to a corolla?"

    Message Count:
    496
    Likes Received:
    70
    Trophy Points:
    308
    Location:
    Maryland
    Vehicles:
    ZZE110
    That's weird. I thought the 1zz short block was identical across the all platforms

Share This Page