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    Thread: DIY: VR6 Exhaust Manifold and Downpipe Porting (Pic Intensive)

    1. Geriatric Member need_a_VR6's Avatar
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      12-24-2007 11:12 PM #1
      I wanted to try and document this a bit while it was still fresh in my mind, but I had a race to get to at the end of the week so it's a been a bit since I did it. However, I will do my best to tell you what I did and why. I lost a few pics of the process but I'll describe the best I can what I did that isn't shown.

      To start off you'll need these:Just one I could only find a pic of four of them. Make sure you get the 6" shank as the manifolds are pretty deep.

      You'll also want a decent air compressor and die grinder that can operate at the speed of your bit for extended periods of time.

      Plan to spend between 4-6hrs on this and it's VERY messy. Be sure to wear eye protection as well as some sort of face mask/respirator. The carbon dust is not fun if inhaled.

      It's easier to start with the downpipe as it's a little easier to get going and get the feel for things.

      Start off by getting the exhaust manifold 'back welded' as seen below:

      This will allow you to fully port the inside of the downpipe, but the welding will leave some 'dingleberries' on the inside:

      You want to get rid of these, as well as try and smooth the transition to gasket size:

      About halfway.

      Complete.

      You'll notice I didn't quite go to gasket size as my weld wasn't THAT big and the transition would be sharp had I gone bigger. This is personal preference but it works. I cleaned that up with a sanding bit but didn't polish it much more then shown.

      Now to the manifolds, these take FOREVER so be patient. Your hands will hurt after a bit, so stop and come back later.

      Starting point:

      Comparison to gasket:

      Ported:

      Notice not only the matching of the gasket but also the smooth transitions around the turns. Getting in there deep is where it matters.

      I only finished it with the grinder plus some 80 grit final finishing. Some will argue that full polishing will hold some power as well. I didn't have the time to find out.

      I don't have pics of the manifold where it meets the downpipe but it's ported just a little less then the downpipe so that there's a step up to it, roughly .5mm large.

      I hope that explains some things about porting the manifolds now that we hear so much about it these days.

      Last edited by need_a_VR6; 05-06-2011 at 02:16 PM.
      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    2. Member cgeromi's Avatar
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      12-24-2007 11:45 PM #2
      Can you explain exactly what porting does? Pardon my ignorance I just am not sure exactly why to do this.

      Awesome DIY tho. Thanks!


    3. Geriatric Member need_a_VR6's Avatar
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      12-24-2007 11:53 PM #3
      In this case you make the exhaust manifold entry larger and smoother, less restrictive and more even across all the cyls.. basically, more power.

      An almost identical setup on my old car made in the neighborhood of 5-7whp over a very expensive aftermarket header at a fraction of the cost.

      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    4. 12-24-2007 11:56 PM #4
      Pimp status... Thanks for doing this

    5. Member cgeromi's Avatar
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      12-25-2007 12:03 AM #5
      Quote, originally posted by need_a_VR6 »
      In this case you make the exhaust manifold entry larger and smoother, less restrictive and more even across all the cyls.. basically, more power.

      An almost identical setup on my old car made in the neighborhood of 5-7whp over a very expensive aftermarket header at a fraction of the cost.

      I figured it would give some HP gain, just wasn't sure how much. It's amazing just by porting those area out you get better HP. Why wouldn't the factory do that from the get go?


    6. 12-25-2007 12:20 AM #6
      It would require more machining, therefore more expensive. Also it makes things thinner, larger chance of things cracking.

      I'm going to bookmark this though. I'm actually picking up a spare cylinder head to port and polish and I'd like to get some ex. manifolds and a lower intake to port too. Along with some 262's and a chip, I should see a good power gain.


      Modified by WeeZFan69 at 5:21 AM 12-25-2007


    7. Member TgiRicky's Avatar
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      12-25-2007 02:22 AM #7
      Hey paul, did you notice any difference at the track? butt dyno?

    8. 12-25-2007 02:42 AM #8
      I did this when I had my CRX and my bone stock 1.6l kept up with my brothers modified ZC 1.6l swap...is a worthwhile mod to do, might consider doing this when the spring comes along or maybe buy a used DP & manifolds and prep them for the spring time...we'll see what happens

    9. Member Joe Amato's Avatar
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      12-25-2007 03:54 AM #9
      Nice work, Paul

    10. Geriatric Member need_a_VR6's Avatar
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      12-25-2007 11:10 AM #10
      At the track it's worth 'about a tenth' which is noticeable, considering most of the time I'm looking for hundredths or thousandths!

      I'll do a DIY of the lower intake manifold I did when I get some time this week as well.

      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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      12-25-2007 12:46 PM #11
      Quote, originally posted by need_a_VR6 »
      At the track it's worth 'about a tenth' which is noticeable, considering most of the time I'm looking for hundredths or thousandths!

      I'll do a DIY of the lower intake manifold I did when I get some time this week as well.

      Have you dyno'd since the port? I'd love to see if you break 200

      In addition, did you backweld the exhaust manifold? It doesn't appear to need it.

      Mike

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      -----------------------

    12. 12-25-2007 01:06 PM #12
      I did this a few years ago and it SUCKED.
      I ended up using 80 grit flapper wheels to finish the insides, then hit it with some rough polishing compound for a nice shiny interior finish.
      At the same time i replaced the stock exhaust with a 2.5" cat back, and a cleaned up downpipe. Net gains was 10 wtq, 7 whp on a car with cams / chip and a few other lil goodies. Ceramic coated by these guys too.
      http://www.nationalcoating.com/body_index.html
      Its not a "appearance" enhancer, and it does retain dirt/stains etc but seems to work.

      If I had to do this again, I'd pick up a used set and take my time until they were perfect.


    13. Member VR6TUNER's Avatar
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      12-25-2007 05:26 PM #13
      This is awesome Paul! Exactly what I was looking for. Thank you very much.

      Merry Christmas!


    14. 12-25-2007 06:09 PM #14
      very nice really makes me want to do this, unfortunatly no compressor, die grinder or garage for me,,

      I did the intake side, but thats aluminum and I used a dremel tool,, any idea if a dremel is powerful enough to do this on cast iron/steel?


    15. Geriatric Member need_a_VR6's Avatar
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      12-26-2007 11:40 AM #15
      I don't know if a dremel would do it, I was having a rough time with the grinder! Wouldn't hurt to try though.
      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    16. 12-26-2007 01:13 PM #16
      Quote, originally posted by need_a_VR6 »
      I don't know if a dremel would do it, I was having a rough time with the grinder! Wouldn't hurt to try though.

      I used my dremel when I did the CRX manifolds and I used sanding rolls too, it just takes longer, but, is doable...


    17. 12-26-2007 02:00 PM #17
      well I had good luck using grinding stones on my intake manifold even though they would gum up quickly due to the aluminum,, i might try this, i'm sure i could find some exhaust manifolds for cheap at a junkyard


      Modified by VW_IS_life at 11:01 AM 12-26-2007

    18. 12-26-2007 05:38 PM #18
      Good info = Pimp Status keep pouring the knowledge Paul.

    19. Member kevwithoutacorrado's Avatar
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      12-26-2007 07:07 PM #19
      dremel will work, but it took me probably 6 hours total and was no where near as deep as these pics. a dremel just can't get deep, and the bits are so small diameter that they disappear fast.

    20. 12-26-2007 07:45 PM #20
      Nice write up! Nothing better than free hp

    21. Moderator yellowslc's Avatar
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      12-26-2007 09:12 PM #21
      http://www.ruffstuff.com is your friend for all porting needs..

      I've done two sets of these.. my personal set and the other for a friend who begged..

      Particulate respirators are a MUST. The cast iron/carbon mix will mess up sinuses for quite some time. Pick up a decent inline die-grinder and be prepared to make an utter mess.

      Butt dyno says they helped.

      R


    22. Geriatric Member need_a_VR6's Avatar
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      12-27-2007 01:14 AM #22
      Quote, originally posted by yellowslc »

      Particulate respirators are a MUST. The cast iron/carbon mix will mess up sinuses for quite some time.

      Even with the mask I was messed up for a few days.

      Oh and my 198whp pull was done with that manifold on the car. That, a Joe head, ported intake and the modded VGI got 11whp at peak and 15whp+ at 7k, even with the 'small' cams.

      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    23. Member
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      01-08-2008 11:47 AM #23
      would it work for the trottle body?

    24. 01-08-2008 04:12 PM #24
      instead of this mod how bout making proper width gaskets?

    25. Member turbo mike's Avatar
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      01-08-2008 04:33 PM #25
      Quote, originally posted by cliffhuxtable »
      instead of this mod how bout making proper width gaskets?

      youre supposed to port the manifolds to fit the gaskets, which helps in hp.

      are you trying to say just make gaskets that fit the stock size of the ports?

      not trying to be a dick, just curious as to what you mean

      Mike
      supercharged glx - 12.0 @ 113mph (12psi Vortech V1)
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    26. 01-08-2008 04:56 PM #26
      Quote, originally posted by -THROTTLE- »
      are you trying to say just make gaskets that fit the stock size of the ports?

      bingo. why do all that work?

      curoius cause i made proper fitting gaskets when putting my new exhaust on.


    27. Member turbo mike's Avatar
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      01-08-2008 07:01 PM #27
      got it. reason to do all that work is bc it actually improves flow, and helps gain some power. just adding a correctly matched gasket wont do anything to improve power or flow. if youre an all motor guy looking for every little bit of power then this is a great idea. if youre boosted, theres other things to do prior, but this helps.

      we will find out soon enough, i just grabbed a set of manifolds/downpipe and will dyno the car again soon.

      Mike
      supercharged glx - 12.0 @ 113mph (12psi Vortech V1)
      turbocharged glx - 12.7 @ 108mph (7psi Borg Warner S362 .88 a/r)

    28. 06-15-2008 10:17 AM #28
      just clarifying why the exhaust manifold is "back welded" as in the first and second pictures.

      is this to add extra strength to the part of the manifold that you are effectively making thinner?

      -steve


    29. Geriatric Member need_a_VR6's Avatar
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      06-15-2008 12:27 PM #29
      It's just the downpipe, welding the outside lets you grind the inside weld out and not have it come apart.
      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
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    30. Member FLATBLACKMK2's Avatar
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      02-16-2009 02:06 PM #30
      good write up sir....
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    31. Geriatric Member need_a_VR6's Avatar
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      02-16-2009 09:56 PM #31
      Thanks, I have to update some of the pictures the next time I do a downpipe.
      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    32. Member mwm2's Avatar
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      04-04-2011 09:24 PM #32
      I planning on porting out a downpipe, but is it going to be pointless if I don't do the manifold too?

    33. Member mwm2's Avatar
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      04-07-2011 05:19 PM #33
      Quote Originally Posted by mwm2 View Post
      I planning on porting out a downpipe, but is it going to be pointless if I don't do the manifold too?
      Bump!!!
      Because I need an answer to this before I start taking my exhaust off.

    34. Geriatric Member need_a_VR6's Avatar
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      04-07-2011 09:50 PM #34
      I wouldn't bother doing the downpipe unless the manifold is done as well.
      -Paul
      1995 GTI VR6 - ??.??@??? 3.6 Power - 12.90@106 R32 power - 12.833@106 12v power
      KPTuned - Official MegaSquirt: Sales - Repair - Installation - Tuning
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    35. Member mwm2's Avatar
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      04-08-2011 09:21 AM #35
      Quote Originally Posted by need_a_VR6 View Post
      I wouldn't bother doing the downpipe unless the manifold is done as well.
      Thanks!

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