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Question On Boost.

Discussion in 'Forced Induction' started by saturn_boy96, Feb 3, 2003.

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  1. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    Okay, i know that psi is just a pressure and when you talk boost what you should really be concerned with is volume so here is my question.

    You have two turbos-
    1. T3/T04 hybrid flowing .5 bar
    2. Mitsu 18g turbo flowing .5 bar

    what is the difference going to be?
     
  2. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    Okay i have to add this cause i am really screwed up right now. both of the turbos are flowing into equal intercoolers with the BOV right in front of the throttle body. that is where the pressure is being measured at.

    if both turbos are flowing into the same thing wouldn't the only variable be spool time? cause you're actually trying to pressurize a certain amount of air space and as more air is forced in wouldn't that increase the pressure? Granted a bigger turbo is going to be able to flow more air but it will take more exhaust to get it to flow? Along with that once the chamber is pressurized the turbo shouldn't matter anymore cause the BOV will open and allow the turbo to spool again. :blink:
     
  3. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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  4. kyleirwin

    kyleirwin Retired OG

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    google. seach for cfm flow rates of the two turbos, nobody is gonna know it off the top of their head.
     
  5. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    oh, i don't really care about the flow rates i just want to know which effects power and how so.

    is it the mass of air

    the pressure of the air

    or the pressure from the i/c?
     
  6. K2e2vin

    K2e2vin Senior Member

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    volume and pressure matters. look up turbo maps for those turbos, see which one is better balanced.
     
  7. pissedoffsol

    pissedoffsol RETIRED

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  8. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    ok. here is my question.

    if a turbo is flowing into an intercooler, doesn't the size of the intercooler matter more than the size of the turbo. eg. a small turbo flowing into a small intercooler would build pressure faster than a small turbo flowing into a large intercooler. at the same time a large turbo would build pressure faster than a small turbo if flowing into the same large intercooler, but once spooled they would both flow the same volume of air into the engine at the same psi.

    is this correct?
     
  9. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Yes, once spooled... but turbo sizing will determine when your turbo is spooled up, how efficient it is while boosting at that level, and how wide your power band looks on the dyno...
     
  10. pissedoffsol

    pissedoffsol RETIRED

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    no.

    intercooler does NOT build pressure. In fact, you LOOSE pressure by running an intercooler- even a good one. sometimes, as much as 2 psi. BUT, you don't know this because your wastegate is set to X psi and will reach it regardless before it starts to waste off.
    Remember- pressure is measured at the intake manifold - not at the turbo or intercooler. And also remember that pressure or PSI is the amount of air NOT going into the motor. its like putting your thumb on the end of a garnden hose. when its just open, a lot of water comes out, but it doesn't go very far. naw- put your thumb on it- the harder you press- the more pressure you build inside the hose- which pushes the water than can get out much faster/harder. thats kinda what a throttle body is- a thumb.

    its a little bit of a bad example- because its not the throttle body closing that builds the pressure- as its open... but the fact that the turbo is pushing in a shit load more air than the engine can take in at any one time.

    no for the turbo question- regardless of the intercooler size, or lack there of- it doesn't really matter.
    a t4 at 5 psi is flowing a HELL of a lot more air compared to a T25 at 5 psi.
    its volume - not pressure. re-read that article i linked above. i think you are still a little confused on it
     
  11. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    ok i totally get it now!!!! i don't know why it was so hard to understan before. the "thumb on hose" explanation makes complete sense now.

    when the throttle body is closed the turbo isn't even spooling, so when the throttle body is open the intercooler can't build pressure cause all of the air is going into the engine. it isn't until you are flowing a higher volume of air than the engine can handle that the BOV wastes. duh!

    thanks you guys for explaining this to me. i feel much more edumacted.
     
  12. K2e2vin

    K2e2vin Senior Member

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    What the cong hell?

    I dunno what you are really saying but intercoolers dont build pressure.--Its about air temp. Cold air is dense=more oxygen. Hot air, vice versa. air leaving the turbo is hot, because of compression, so its not as dense. it the goes into the intercooler, which cools it and makes the not so dense air dense. this causes a pressure drop. The BOV opens when the throttle body is close which prevents excessive pressure buildup, which can cause the pipes to explode.
     
  13. pissedoffsol

    pissedoffsol RETIRED

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    no. the wastegate bleeds bosot pressure to regulate. a BOV is simply a device to protect your turbo. its allows the gases once the TB is closed to leak out instead of spinning the turbo backwards. backspin is the #1 cause of turbo failure.

    and even when the throttle body is closed, the intercooler will not build pressure.
    once the TB is closed, most to all gases exit the BOV. since honda's use a MAP, and not a MAF, you will NEVER make boost at idle or when there is no air getting to the MAP, which is on the TB.
    DSM's on the other hand can rev up and let off- and the BOV will go off- thats cuz its boosting and reading off their MAF. a Honda, unless something I don't know about is going on, will never build more than .1 psi of boost at idle unless they have a stupid crazy small turbo and have wicked exhaust flow at idel.


    yeah it is. there is still a combustion cycle that happens AFTER you close the TB. the air has gone in, the gas will come out and thus turn the turbo at least for a 1/4 of a second.


    again, this is all regulated off the wastegate via a vacuum line.

    Are you SURE you got it that time? :lol:
     
  14. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    if the throttle body is closed the turbo is spooling so slowly the pressure it is creating will not really increase performance.



    Are you saying pressure doesn't build within the intercooler and piping when the turbo is forcing air into it?


    Wastegate= exhaust side of turbo(on exhasut mani)

    BOV=intake side of turbo(near intake mani before TB)

    right?


    are you saying that the bov only opens when the throttle body is closed and the only thing that regulates boost pressure is the wastegate?

    i am so dumb?!?!?!?!
     
  15. K2e2vin

    K2e2vin Senior Member

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    yeah pressure builds up but the pipe leading to the intercooler has more pressure than the pipe exiting the intercooler, but thats when the TB is open and the turbo is building pressure.

    yes BOV is on the intake side and wastegate is on the exaust side.

    as far as i know if the wastegate opens the BOV stays closed unless theres more pressure, as BOVs open at a predetermined pressure eg. reaching redline. but when you change gears theres an emense amount of pressure that builds up when the TB closes (think about how fast the enigine is sucking up air and more pressure on it; .9cc of air per revolution is sucked in, and engines running around 8k)
     
  16. pissedoffsol

    pissedoffsol RETIRED

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    exactly.

    the wastegate regulates your psi.
    the bov, protects your turbo by releasing excess.

    nothign more, nothing less
     
  17. K2e2vin

    K2e2vin Senior Member

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    hey i never asked that question. are you trying to set me up? jp
     
  18. saturn_boy96

    saturn_boy96 88 C1V1C 53D4N DR1V3R

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    Ok, now i think i got it. I thought that the BOV regulated pressure and the wastegate protected your turbo.

    So now i think i uderstand. The only thing that really matters is volume of air not psi. A tiny turbo will create a lot of psi but will not be able to flow the volume of air that a big turbo will.


    :worthy: :worthy: :worthy: pissedoffsol's knowledge of boost

    Thanks for your help.
     
  19. Hexen

    Hexen Senior Member

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    You are learning Saturn Son.

    :)

    When people are like "I WANT TO RUN 20 PSI YO!"... that is a really annoying statement.
    PSI has nothing to do with the horsepower gains you're going to get from airflow. (Specific PSI numbers that is).

    A more logical thing to look at is... I want to run XX.XX time in the quarter mile... let me get my car dyno'd to see where my detonation point is. If I can't run XX time with XX amount of boost that my car can handle.. it's time to buy more parts :p
     
  20. No_Illusions

    No_Illusions Junior Member

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    Boy things really got screwed up in here. It all about how much of a mix of 14:1 fuel air ratio you can get. Intercoolers allow more air to get in at the same psi than running without one. So air flow, psi and air temp all work together you can't just say airflow doesn't matter, it does as much as the other two if not you could just use the 5 psi emissions pumps to make a supercharger. ( THAT IS NO JOKE MY NEIGHBOR TRIED IT STUPID PEOPLE LIKE THAT SHOULD BE HANGED< OF COURSE HE DID DRIVE A MUSTANG)
     
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