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What Compression Ratio

This is a discussion on What Compression Ratio within the Forced Induction forums, part of the LSx Technical Help Section category; Im gonna be getting a 346 Long block with LQ9 heads and a custom cam. this is going in a ...

  1. #1
    Senior Member JD_Z28's Avatar
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    What Compression Ratio

    Im gonna be getting a 346 Long block with LQ9 heads and a custom cam. this is going in a 02 Z28 with an STS kit. I just wanted to get some opinions on what compression I should shoot for. What pistons should I use.

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    Member SKULLZ's Avatar
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    8.5:1 should be ok, Im no forced induction expert but the lower your compression ratio the more boost you are able to run. Im sure its vendor specific on certain amounts of boost, if you want LOTS and LOTS of boost then 7.5:1 or 6.5:1 compression would work as well. It all depends on what you want to do with the car, street, strip or both. I would contact STS and get their opinion. Feel free to correct me too

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    The Masterpiece Qwk94Z28's Avatar
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    Quote Originally Posted by SKULLZ
    8.5:1 should be ok, Im no forced induction expert but the lower your compression ratio the more boost you are able to run. Im sure its vendor specific on certain amounts of boost, if you want LOTS and LOTS of boost then 7.5:1 or 6.5:1 compression would work as well. It all depends on what you want to do with the car, street, strip or both. I would contact STS and get their opinion. Feel free to correct me too
    7 and 6 compression ratios


    usually a 8.5-9.0 is a good ratio but think of it as this. if you can cool your combustion temps and run good gas you'll be fine

    before i moved to the v8s i had a n/a car that i turbocharged. 9.5:1 stock 10psi stock internals just ran a front mount and 94 and i was fine in 100* weather.

    also if you run a lower compression it'll take more boost to make the same power as someone running a little bit higher and less boost

    but 6:1 no offense

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    Member SKULLZ's Avatar
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    Quote Originally Posted by Qwk94Z28
    7 and 6 compression ratios

    but 6:1 no offense
    none taken but it really depends on what you want to do with the car if its a DD then yes 9.5:1 but for a track car I would go lower

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    The Masterpiece Qwk94Z28's Avatar
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    1998 Z28-408 l92 stroker

    i've never seen a built engine below 8.5:1 tho, if its gonna be a track car then shit run 10:1 compression some 110 octane and some h2o/alky injection.

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    ITLXLR8
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    Quote Originally Posted by Qwk94Z28
    i've never seen a built engine below 8.5:1 tho, if its gonna be a track car then shit run 10:1 compression some 110 octane and some h2o/alky injection.

    Ive seen built motor's below 8.5:1.......
    Some in the high 7"s
    I wouldnt go lower then 8.5:1 though.
    Im 8.8:1 in my current motor and ill only be running pump gas on low boost for the street and all out 20+ psi with C16 only for the track......
    Instead of asking most guys on here.. call up an engine buildet that has built many boosted motors and pick there brain........

    Kyle

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    Registered Player brad8266's Avatar
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    Quote Originally Posted by SKULLZ
    none taken but it really depends on what you want to do with the car if its a DD then yes 9.5:1 but for a track car I would go lower
    Pure track cars can run high compression and high boost, they just use alcohol or other extremely high octane fuel. I am shooting for 9.0-8.5:1 for when I install a blower.

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