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    Thread: Is 20PSI on K04 equal to 20PSI on GT28? i think no my friend thinks yes

    1. 05-09-2012 09:05 PM #26
      Said simply:

      A bigger turbo will have cooler, denser air (read:more oxygen) at a given PSI than a smaller turbo, all things being equal.

      More oxygen means more bang bang.

      More bang bang means more zoom zoom.

    2. Member silverA4quattro's Avatar
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      05-09-2012 09:05 PM #27
      Quote Originally Posted by BlackA4stage3 View Post
      ok so here is what happened. a few days a ago i saw another B6 A4 guy drive by me so i followed
      Did you cup his balls?

    3. Member BlackA4stage3's Avatar
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      05-09-2012 09:08 PM #28
      Quote Originally Posted by silverA4quattro View Post
      Did you cup his balls?
      yes. i was on my way to class and saw the only other modded audi in statesboro GA so i had to creep. ended up skipping class. thats Audi dedication

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      05-09-2012 09:11 PM #29
      You will just build your 20psi faster and reach peak hp quicker thats all 20psi is the same whether it be a small or large turbo. your just pushing more air to build 20 psi before the smaller turbo, its a pretty simple answer...

    5. 05-09-2012 09:16 PM #30
      I thought a turbo forced an exhausted mixture which has very little O2? Most would have been exhausted in the initial cylinder detonation. I wonder if the difference in exhausted gases would even be a factor? I thought the pressurized exhaust from the turbo provides the energy, not the O2?

      Quote Originally Posted by DIAF View Post
      Said simply:

      A bigger turbo will have cooler, denser air (read:more oxygen) at a given PSI than a smaller turbo, all things being equal.

      More oxygen means more bang bang.

      More bang bang means more zoom zoom.

    6. 05-09-2012 09:19 PM #31
      Quote Originally Posted by LhW View Post
      I thought a turbo forced an exhausted mixture which has very little O2? Most would have been exhausted in the initial cylinder detonation. I wonder if the difference in exhausted gases would even be a factor? I thought the pressurized exhaust from the turbo provides the energy, not the O2?
      No, the exhaust spins the hot side and then continues out the tailpipe.

      On the other side of a nice bearing is the cool side, which pulls air in through the intake.

      Intake air is not exhaust air. You are thinking of DEI.



      :lol:

    7. 05-09-2012 09:23 PM #32
      Ahhh - I got it. The illustration is classic!

      So, 02 does play a factor. News to me. Thanks for the info.



      Quote Originally Posted by DIAF View Post
      No, the exhaust spins the hot side and then continues out the tailpipe.

      On the other side of a nice bearing is the cool side, which pulls air in through the intake.

      Intake air is not exhaust air. You are thinking of DEI.



      :lol:

    8. Member Slayer's Avatar
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      05-09-2012 09:25 PM #33
      PSI = a measure of resistance, so "boost" does not equal horsepower. What you want is CFM. That's a measurement of flow, and all a motor is, is an air pump. The more you can push through it, the more HP you can make.

      A small turbo can reach 20psi, yes, and a large turbo can also reach 20psi. Difference is that with a larger housing, you can flow more cubic feet of air per minute than a smaller housing. Think of it this way: 20Psi of air through a 3ft diameter pipe flows more air than 20Psi of air through a 1/4" pipe

      Anyone that tells you 20 psi = 20 psi has no clue what they are talking about
      Check out my Garage build thread 2008.5 GTI 2.0 TSI 6MT / APR K04 V3.1, APR IC, CTS 3" turbo back, Carbonio full intake, GFB DV+, BSH TB pipe, SB Stg2 Endurance clutch, BSH mounts, DG Shortshifter, FFM bracket bushings, Forge big knob, Koni coils, Coolingmist CMGS Meth injection, USRT spacer (DO3 & Snow 100 nozzles), 19" Miro stp3's, Centric rotors, Stoptech pads and TyrolSport bushings

    9. 05-09-2012 09:26 PM #34
      Quote Originally Posted by LhW View Post
      Ahhh - I got it. The illustration is classic!

      So, 02 does play a factor. News to me. Thanks for the info.
      There are three things that matter in motor - fuel, air, and spark (hidden fourth would be timing).

      If you add more of the three proportionally, you get more power.

    10. Member overst33r's Avatar
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      05-09-2012 09:33 PM #35
      Quote Originally Posted by Shomegrown View Post
      So who's not going to read the thread and be the next to post the straw/garden hose analogy?
      wait for it...

      Quote Originally Posted by Slayer View Post
      Think of it this way: 20Psi of air through a 3ft diameter pipe flows more air than 20Psi of air through a 1/4" pipe
      ...and there it is.


      135
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    11. Member Slayer's Avatar
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      05-09-2012 09:41 PM #36
      Quote Originally Posted by mariok2006 View Post
      wait for it...



      ...and there it is.
      guilty as charged lol. I say the same thing every time this comes up
      Check out my Garage build thread 2008.5 GTI 2.0 TSI 6MT / APR K04 V3.1, APR IC, CTS 3" turbo back, Carbonio full intake, GFB DV+, BSH TB pipe, SB Stg2 Endurance clutch, BSH mounts, DG Shortshifter, FFM bracket bushings, Forge big knob, Koni coils, Coolingmist CMGS Meth injection, USRT spacer (DO3 & Snow 100 nozzles), 19" Miro stp3's, Centric rotors, Stoptech pads and TyrolSport bushings

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      05-09-2012 09:42 PM #37

    13. 05-09-2012 09:42 PM #38
      You can pump 20 PSI through a garden hose and you will get less PSI than pumping 20 PSI through a straw. What matters is the setup to get the PSI out of whatever size turbo is on the engine. So, a larger engine will be able to move more PSI through the turbo.

      A 2 liter 4 cylinder engine would not able to move 20psi through a large turbo. A 4 liter six could easily move enough air through a large turbo to gain 20 PSI. A larger turbo, as stated earlier in another reply, is moving much more air that than a smaller turbo at 2 liters.

      I think that is the missing piece of this discussion that has not been addressed. Everyone has been talking around that without mentioning it?



      Quote Originally Posted by mariok2006 View Post
      wait for it...



      ...and there it is.

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      05-09-2012 11:04 PM #39
      PSI = a measure of resistance, so "boost" does not equal horsepower. What you want is CFM. That's a measurement of flow, and all a motor is, is an air pump. The more you can push through it, the more HP you can make.

      A small turbo can reach 20psi, yes, and a large turbo can also reach 20psi. Difference is that with a larger housing, you can flow more cubic feet of air per minute than a smaller housing. Think of it this way: 20Psi of air through a 3ft diameter pipe flows more air than 20Psi of air through a 1/4" pipe

      Anyone that tells you 20 psi = 20 psi has no clue what they are talking about
      First psi and flow is what your looking at, and they are two different measurement dynamics. Once you reach 20 psi all flow stops, make sense so all in all the size of the turbo alone doesn't mean anything If ou don't have the motor to take in all the flow then your just throwing money out the window a small turbo can easily out perform a larger one if everything is done correctly ...

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      05-09-2012 11:10 PM #40
      Quote Originally Posted by LhW View Post
      You can pump 20 PSI through a garden hose and you will get less PSI than pumping 20 PSI through a straw.
      thats makes no sense whatsoever...

      you mean flow right because pressure plays no role in that.

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      05-10-2012 12:13 AM #41
      Quote Originally Posted by LhW View Post
      You can pump 20 PSI through a garden hose and you will get less PSI than pumping 20 PSI through a straw. What matters is the setup to get the PSI out of whatever size turbo is on the engine. So, a larger engine will be able to move more PSI through the turbo.

      A 2 liter 4 cylinder engine would not able to move 20psi through a large turbo. A 4 liter six could easily move enough air through a large turbo to gain 20 PSI. A larger turbo, as stated earlier in another reply, is moving much more air that than a smaller turbo at 2 liters.

      I think that is the missing piece of this discussion that has not been addressed. Everyone has been talking around that without mentioning it?
      Are you being facetious?

    17. 05-10-2012 12:32 AM #42
      And now I remember why I stay out of the joke that is the Car Lounge.



      "Boost" measurement is a measure of restriction in the inlet path. Not power, not power potential, ect.
      It is dictated by overall Pumping(Volumetric) Efficiency of the engine as a whole. Everything you do to create power, is done by either increasing the VE of the engine, or by external "power adders" such as nitrous, and FI.

      With that said, a certain turbo is only capable of flowing enough Lb/hr(NOT CFM as someone else stated, as that doesn't take density into account which is a HUGE player in FI) to provide the engine with enough oxygen to make X amount of power at X shaftspeed. Shaftspeed can be increased, with diminishing returns past a certain point, which will increase intact tract pressure AKA PSI. Lb/Hr is mainly dictated by the compressor side of the turbo, as is outlet temps, and therefor IAT's. The turbine side mainly dictates spool characteristics, and effects the Pressure Ratio of the engine, which is VERY important when trying to take a engine/turbo combo to it's full potential.



      A "K04" (Which is INSANELY in-descriptive) will 99.9% of the time flow much less lb/hr then a "gt28" (which again, is very undescriptive, and only tells us 1/6 of the turbo specs.)

      I would post the compressor maps for each of the turbos so you can see for yourself, but that would be a waste of bandwidth in the Car Lounge, as noone here would understand them.


      So, no, 20PSI is not 20PSI in a restriction aspect/FI aspect. "Flowing" PSI is not the same as "Stagnant" PSI. In any application.

    18. Member stascom's Avatar
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      05-10-2012 12:38 AM #43
      Quote Originally Posted by Shomegrown View Post
      OK, the answers here are mostly right, but for the mostly wrong reasons!

      To understand, you need to look at the basics - what is boost?

      Positive boost pressure occurs because there is more air being forced through the engine than the engine can ingest using its own volumetric efficiency.

      Changing to a larger turbo does not have a significant impact on VE or the volume of your intake system, nor is it the most restrictive part of the intake (that's the throttle) so the "blowing through a straw" analogy is way off base. It doesn't apply at all.

      The reason larger turbos usually make more power for the same relative boost level is twofold:

      1.) Compressor wheel efficiency leading to lower IAT
      2.) Lower TIP (turbine inlet pressure or less exhaust restriction)

      What this means is if the IAT is the same and the exhaust backpressure is the same, then 20 psi on turbo X will absolutely equal 20 psi on turbo Y even if the turbos are sized differently.

      Now, both factors 1 and 2 can be controlled outside of turbo size. Let's pretend...

      Car # 1 has the smaller K04 but open dump pipes and a huge FMIC with meth injection

      Car # 2 has the larger GT28 but smaller intercooler and a quiet exhaust with cats

      Under those conditions, it would be possible that the Car #1 performs better at 20 psi than Car #2.

      Long story short, boost pressure is restriction in the engine, not the turbo. So 20 psi = 20 psi unless other properties are changed (VE, IAT, TIP, etc).

      So who's not going to read the thread and be the next to post the straw/garden hose analogy?
      This is great for academic discussion and theorizing. But IRL, I would imagine, both turbos are matched with appropriate intercoolers and exhausts, that is - bigger turbo = wider piping, large exhaust and intercooler.
      Last edited by stascom; 05-10-2012 at 12:40 AM.

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      05-10-2012 12:40 AM #44
      20psi is like stage 4 which requires a fmic and bigger injectors. you need back pressure to cap the flow so be sure and wastegate behind your o2. get an afpr and boost the vacuum so you get max output. then tune it like a mofo and backlog that **** till the cows come home. race. win.
      Quote Originally Posted by Amsterdam087 View Post
      its not your car...

    20. Member stascom's Avatar
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      05-10-2012 12:42 AM #45
      Quote Originally Posted by LhW View Post
      You can pump 20 PSI through a garden hose and you will get less PSI than pumping 20 PSI through a straw. What matters is the setup to get the PSI out of whatever size turbo is on the engine. So, a larger engine will be able to move more PSI through the turbo.

      A 2 liter 4 cylinder engine would not able to move 20psi through a large turbo. A 4 liter six could easily move enough air through a large turbo to gain 20 PSI. A larger turbo, as stated earlier in another reply, is moving much more air that than a smaller turbo at 2 liters.

      I think that is the missing piece of this discussion that has not been addressed. Everyone has been talking around that without mentioning it?
      Same car, same engine.

    21. Member mr lee's Avatar
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      05-10-2012 12:43 AM #46
      Quote Originally Posted by stascom View Post
      Same car, same engine.
      same size/length of pipe and coolers?
      Quote Originally Posted by Amsterdam087 View Post
      its not your car...

    22. Member stascom's Avatar
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      05-10-2012 01:02 AM #47
      Quote Originally Posted by mr lee View Post
      same size/length of pipe and coolers?
      We don't know that. But the guy was making the point on engine displacement when OP has already stated that the cars are the same.

    23. Member RogueTDI's Avatar
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      05-10-2012 01:24 AM #48
      Quote Originally Posted by BlackA4stage3 View Post
      ok so here is what happened. a few days a ago i saw another B6 A4 guy drive by me so i followed

      him and he pulled over and we talked about our cars for a little. he said that he had a K04 setup

      running 20PSI of boost. so blah blah blah later that day im talking to my friend about his car and i

      tell him yea he is running a K04 at 20PSI. so he says "so its basically as fast as your car". i drive a

      B6 A4 with a GT28 running 20PSI boost. so i say no my car would be faster because it is bigger

      running the same PSI. so he says 20PSI is 20PSI. we argued for a good 30 minutes and couldnt

      come to a conclusion. i figured since its 20PSI in a bigger turbo it would be moving more air. Can

      someone tell me if im an idiot or right or what????? ive searched google and couldnt find a clear

      explanation. please help!!!
      You are more or less correct. But it all depends on the turbo performance/efficiency and engine specs. In fact, depending on rpm and turbo design, i think it is conceivable ur bigger turbo would make less power ("at 20psi").

    24. 05-10-2012 01:34 AM #49
      Why is it, that 99% of the people in the car lounge, decide that it's a good idea to spew garbage out of their mouths at every opportunity, without the slightest understanding of what they speak.


      If you have no clue what you are talking about, stop trying to give what you THINK is advice and information, because all you are doing is posting worthless misinformation, and that makes you look like a huge tool.

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      05-10-2012 01:40 AM #50
      Quote Originally Posted by Slayer View Post
      guilty as charged lol. I say the same thing every time this comes up
      Theres actually not much wrong with the analogy, to help the lay person understand. Basically, a bigger pipe will flow more fluid, more efficiently, than a small pipe. Pushing same amount of air through smaller pipe takes more work and heats up the air, making it less dense. Small turbos trying to move too much air just spin faster and faster without compressing it.much more, just heating it up instead.
      Last edited by RogueTDI; 05-10-2012 at 01:44 AM.

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