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    VWVortex


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    Thread: half of a 4.2l 40v head....????

    1. Member
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      04 Golf 1.8T
      10-05-2012 12:18 PM #26
      Quote Originally Posted by 1999.5GTIVR6 View Post
      Hmm yeah this is very true, I completely overlooked the turbo

      Well what can we do to increase the flow of our heads, obviously oversized valves and tons of goodies.
      But if we were to re design the head inorder to allow use to flow what the competition is flowing.
      I need to learn a bit more of how our head flow.
      In my mind I think we are being limited due to velocity,and turbulances build up on our intake but if I'm
      not mistaken we are more limited to our exhaust flow then intake flow correct? Adjust duration and lift and you will see more flow or less. Is there a formula to calculate this with 1mm larger valves ? How much additional flow could be expected? Or are they a suffiecnt size, and the abgle they are on limit them?

      I understand that in order to achieve better flow results when porting and plishing you should spend a lot of time on the valve job and throat areas (this is where we nice gains)

      Wouldn't you see larger flow numbers on tubular manifolds over logg? Or do they not affect flow overall throughout the head (both are large enough to not inhibit the flow)
      One step at a time my friend... you're spiralling out of control here.
      For a basic lesson in fluid dynamics you can get some good information on google, which will include many archived threads from this forum.

    2. Member
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      10-05-2012 12:52 PM #27
      So your saying the cfm and velocity isn't related ? If we improve the turbulence inside the head it wouldn't flow more? Or simply saying the velocity characteristics isn't what limits our cfm.

      What's the stock velocity of these heads? Aeb vs awp? fps.
      What exactly controls the air speed though. From the top of my head you would have different variables for every motor right? Like you need your head to flow the necessary flow to support a the engines displacement (which changes with strokers) and rpm band. If your ports are to large to flow a good inertia wouldn't we see a drop in voliumetric efficiency? So for larger motors and high rpm motors larger ports be ideal but small ports are better for power below 5000pm and smaller motors.

      So if someone were to port and polish their head adding some sort of velocity stacks and and knife edging exhaust on the exhaust side. Make for less resistance for the flowing air, and in turn it moving faster through the head

    3. Member
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      10-05-2012 01:14 PM #28
      So you're question is... will machining work and upgraded components yield increased power output? Or is this all rhetorical? I think you need to do some reading before asking fundamental questions regarding cylinder head flow, or this thread will get out of hand.

      CFM and velocity are obviously related. Q = V x A
      You can port the head to increase area, improve manifold characteristics and runner size to increase velocity and area. If your area is too big for the displacement of the motor you decrease velocity. Etc. Etc.

      The variables are all the same no matter what make or model

    4. Member
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      10-05-2012 01:39 PM #29
      Yeah, I obviously have a lot more reading and learning to do.
      The questions I was asking were all theory based,

      I'm just have trouble finding good resources to start learning from, I have some general concepts but need a good foundation to build on. Not asking to be spoon fed information, but does anyone know a good place to start learning and reading it seems ill read hours into stuff but then get hung up on basics again. .

    5. Moderator groggory's Avatar
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      10-05-2012 02:02 PM #30
      Quote Originally Posted by 1999.5GTIVR6 View Post
      Yeah, I obviously have a lot more reading and learning to do.
      The questions I was asking were all theory based,

      I'm just have trouble finding good resources to start learning from, I have some general concepts but need a good foundation to build on. Not asking to be spoon fed information, but does anyone know a good place to start learning and reading it seems ill read hours into stuff but then get hung up on basics again. .
      http://www.amazon.com/Modern-Engine-.../dp/0854299785
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      My FAQ / DIY Thread -- Look here for 90% of the questions you have

      Welcome to the world of racing! Budgets are ALWAYS exceeded, deadlines are never meet, end-goals never reached, and wives always unhappy... it's all worth it though!

    6. Member Issam Abed's Avatar
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      10-05-2012 09:38 PM #31
      is this 2004?
      Seriously the 4.2 heads are a complete PITA to make work.
      Even if you wanted to take full advantage of the rocker arm set up , you will still need custom cams (don't try and run the V8 stock cams unless you want to bend all your valvetrain using it on a 4 cylinder) as well as custom valvetrain as the S8 internals are slightly different to off the shelf 06A 1.8T components.

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