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Basic boost question

Discussion in 'Forced Induction' started by zueke, Oct 29, 2002.

  1. zueke

    zueke Senior Member

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    Basic, probably easy to answer question.

    Okay, in my question for turbo knowledge this is what I understand. The bigger the turbo, the longer the turbo lag, but the more power it makes at the upper powerband. I also understand that with a larger turbo, since it pushes more CFM of air, you can't run as much PSI as a smaller turbo that pushes less CFM of air. (assuming everything else with the engine is constant)
    But since you can handle more psi of boost with a smaller turbo than a larger turbo, does that higher PSI make up for at all the lack of CFM the smaller turbo has?

    If this makes sense, then someone please shed some light. :worthy:
     
  2. honda_power69

    honda_power69 Member

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    I'm not quite sure where you're coming from there, but... as far as I know, the larger the turbo, the more potential for higher psi. Thats why all of these 8 second pro drag FWD 4 cylinders are pushing over 30 psi of boost. The turbos are absolutely huge. But, as you stated, there is quite a bit of lag associated with them, the turbo actually doesn't "kick in" until about mid-track (give or take). Did that answer your question?
     
  3. SolReaver

    SolReaver Senior Member

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    But since you can handle more psi of boost with a smaller turbo than a larger turbo, does that higher PSI make up for at all the lack of CFM the smaller turbo has?



    hmm thats a good question. PSI or CFM? I bet it would depend on the motor and turbo.
     
  4. Baker

    Baker Senior Member

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    just get a huge ball bearing turbo and a 55 shot and get rid of the lag problem ;)

    honestly as far as your question I have no clue
     
  5. pissedoffsol

    pissedoffsol RETIRED

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    psi means jack and shit in all reality- but for some reason, its a standard. PSI is the measurement of pressure NOT going into the engine at the inatake manifold. (hence, why we need to replace the MAP sensor, missing link it , or honda it, to accept boost)

    So to answer your question--

    low cfm, high boost VS high cfm low boost

    in all reality, given standards, it would be about the same. Thats why you read these supras are making 654 horse of 18 psi.
    yeha- they are running dual t66 turbos or something.

    18 psi on a t-12 is like 7 horsepower. lol

    or 23123 psi off those ebay superchanrgers
     
  6. knowledge

    knowledge Senior Member

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    Yeah the larger turbo's usually lag more, but it all depends on the trims of the turbine blades! Also If you are pushing lets say 15 psi out of a larger turbo you will get more HP gains out of it instead of using a smaller turbo at 15psi. CFM's and PSI are two different measurments. You cannot run safely 15psi on a large turbo but could run 15psi on a smaller turbo because of the difference in CFM's(thoretically).
     
  7. zueke

    zueke Senior Member

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    Thanks for the replies and information. I was just basically asking if you could counteract the small horsepower gains (especially at high RPM) of using a small turbo by pushing alot more PSI....
     
  8. lsvtec

    lsvtec GNU/Linux Evangelist

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    Moving to boost...
     
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