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What compression ratio for turbo?

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  • BLOZ UP
    started a topic What compression ratio for turbo?

    What compression ratio for turbo?

    600whp on whatever 2 turbos will get me it at the lowest boost...

    9:1?

    8.5:1?

    I have no clue.

  • G-E
    replied
    exactly.... you could do a diamond with t/b on both sides, or maybe even a log with one at each end

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  • BLOZ UP
    replied
    G-E wrote: perhaps you should make a custom plenum, perhaps even with twin throttle bodies feeding a common chamber

    you could use two smic's like a z32 but better ones at have them up front somewhere and you can keep the piping super short.... or you could even use the standard end to end outlet style where the left and right turbos feed opposing throttles ... would look hella cool and piping diameter could be small
    I had entertained the dual TB idea for a while. I'm not in the mood to weld aluminum plenums anytime soon. Ugh. piping I can do, but welding on cast is a pain. I suppose I could make a complete one from scratch and I wouldn't have as much of a problem.

    Leave a comment:


  • G-E
    replied
    perhaps you should make a custom plenum, perhaps even with twin throttle bodies feeding a common chamber

    you could use two smic's like a z32 but better ones at have them up front somewhere and you can keep the piping super short.... or you could even use the standard end to end outlet style where the left and right turbos feed opposing throttles ... would look hella cool and piping diameter could be small

    Leave a comment:


  • BLOZ UP
    replied
    So, 8:1.

    I knew there was a trade-off, as GE noted. But I don't know where it is.

    I know I'd need about 28psi to get 600hp, if my little turbo calc is right.

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  • Jason84NA2T
    replied
    It's all going to depend on the type of gas you plan to run, because as GE noted it's a matter of peak cylinder pressure and the fuel stability.

    I would say somewhere around the low 8's is going to be your best bet if you're still planning on the twin 16G's.

    Leave a comment:


  • G-E
    replied
    but remember boost+atmosphere x compression = huge

    at 15psi boost your peak cylinder compression is around 260psi prior to boom on a 9:1

    at 20psi boost it'll be like 10psi higher using 8:1

    that's part 1.... part 2 is how much cylinder pressure reaches on ignition, and that's also a multiple of the peak compression

    so the point is you can lose 10hp to lower compression and make 50hp back by raising boost...

    for 600hp I'd shoot for low 8.x:1 .... the boost will have to be way up there, high 20's/low 30's maybe

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  • FlawleZ
    replied
    If you're running a twin setup and low boost applications, why don't you go ahead with the 9:1? Of course more low end and more air to spool the turbos sooner.

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  • BLOZ UP
    replied
    Sounds good.

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  • Alex86na2t
    replied
    8.5:1 is the universal intermediate. Even the GTP car used it. I know a few people including myself here are using that.

    Leave a comment:

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