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    Thread: 42mm vs 50mm Intake Manifold

    1. 03-23-2005 10:17 PM #1
      I know this is a topic that has been beaten to death I'm sure but here goes anyways. I searched most any pertinent topic on it and never really got what I was looking for.

      Here goes. I am build a engine for my Corrado. I am going to be running the G60 block with a 16v head. I bought a 50mm Scirocco Intake Manifold that will be coming in shortly.

      What I have heard and read in one thread was that the plenum is smaller on the 50mm then on the 42mm. Is this true? if so is it a hugh diference or are we talking about just a very small amount.

      Also if it si a big difference would it be worth making a Frankenstein Manifold by using the plenum off the 42 and the runners off the 50. I also read that someone did this but not who or how it came out.

      I am going to be spending alot on this build up of the car I am not really worried if it costs me a few hundred dollars for something that si going to flow significantly better.


    2. 03-24-2005 06:47 AM #2
      powerdubs is the 50mm hacker...

      IIRC he made more power @ a higher rpm.


    3. Senior Member PowerDubs's Avatar
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      03-24-2005 08:14 AM #3
      Here is the difference of my 50mm manifold w/ a 42mm plenum and shortened the runners 1.5 inchs.

      This was on a stock 2.0 engine w/ around 100k, euro cam, GIAC chip, TT catback, Velocity TB, eurosport airbox, ABD intake tube. (very mild, just bolt-ons.)

      It shows definate promise for anyone looking to make more high end power cheaply. Even on this mild engine it made over 10hp up top and allows you to hold eacxh gear much longer.

      Hopefully within a few months I will be doing dyno testing of it again on a much more 'built' engine.

      Have fun welding the aluminum..


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    4. Member chois's Avatar
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      03-24-2005 03:56 PM #4
      Sounds like an awfully low compression motor you're building, unless there are custom pistons in the plans. A 'high compression' 8v with a 16v head brings a decent boost application compression ratio. Going with the low compression G60 may not be what you want.
      Chris
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    5. 03-24-2005 09:05 PM #5
      Yeah its gonna be a 1.9L running 8 to 1 compression. Its also gonna have a Twin Screw S/C (lysholm) attached to it. Yeah I posted it in this forum rather then the G60 forum because I figured I'd get a better response.

      The info and pics was what I was looking for. As far as welding the aluminum as much as I'd like to say I'll be doing that work myself it's going to be professionally done.

      My 50mm manifold was supposed to come fed ex today but with the snow they must have gotten delayed.


    6. 03-25-2005 12:06 AM #6
      Hey Powerdubs, did you polish the plenum while it was apart? Being there is no gas mixed into the air at this point, polishing it would be a wise idea, it seems to my mind. Atleast smooth out any sharper edges.

      I just don't have the guts to cut up a 50mm.


    7. Senior Member PowerDubs's Avatar
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      03-25-2005 12:53 AM #7

      -Josh
      Current- 06 Phaeton 4-seater 6.0 W12 | 04 VW R32 | 03 Gti 24v VR6 | 00 M Roadster | 12 Kia Soul 1.6 stick | 01 ZRX1200R | 03 KLX400R
      Past- too much too list.

    8. 03-25-2005 05:12 AM #8
      lol - I swapped from 42mm to 50, gained 1bhp and lost about 8lbs peak torque

    9. 03-25-2005 09:57 AM #9
      what's the advantage of the 42mm plenum? was it to lengthen the intake after shortening the runners?

    10. Member AndrewDaniels's Avatar
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      03-30-2012 09:53 AM #10
      Quote Originally Posted by G_V_K View Post
      lol - I swapped from 42mm to 50, gained 1bhp and lost about 8lbs peak torque
      Haha that sucks.
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    11. Member rysskii3's Avatar
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      03-30-2012 11:29 AM #11
      when i switched to 50mm intake mani, i felt a substantial difference in power and torque. car felt much faster.
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    12. 03-30-2012 04:45 PM #12
      Quote Originally Posted by 20V'er View Post
      I just don't have the guts to cut up a 50mm.

      you mean like this







      love this mod!

    13. Member lnoriel's Avatar
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      03-30-2012 05:04 PM #13
      I took a look at my US 42mm and laid it directly on top of the European 50mm. The plenum from my perspective looked identical in size judging from the exterior.

      I used a ruler on the height and width and the exterior dimensions were the same on both. But the depth is nearly 1 inch shorter on the Euro.

      Of course, it is inside dimensions that would have to be compared. I don't know how one would compare the internal volume of the plenum.

      Im sure there are flow bench comparisons which can be found online. I would think that really is the only performance related criteria that would matter.
      Last edited by lnoriel; 04-01-2012 at 01:16 PM. Reason: Added more info and picture
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    14. Member Road Boss's Avatar
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      03-31-2012 01:11 PM #14
      I'm debating on getting one too. I just might just polish the inside of my 42mm and go with that.

    15. Member lnoriel's Avatar
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      04-01-2012 01:24 PM #15
      Quote Originally Posted by Road Boss View Post
      I'm debating on getting one too. I just might just polish the inside of my 42mm and go with that.
      I had read an article awhile back in European Car that highlighted a Eurosport modified 16V. In the article, they had ExtrudeHoned a 42mm US spec intake manifold and said it had better flow characteristics after the internal treatment than the Euro 50mm in its stock form. Of course, ExtrudeHone is the pinnacle of fluid dynamics in terms of internal porting & Polishing. I'm sure the same treatment on a 50mm would truly be awesome for a normally aspirated motor.

      I'm no expert in forced induction, but I would imagine that if high intake manifold pressures are your goal, then the smaller bore 42mm intake manifold would probably better suit your application.
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    16. 04-01-2012 05:35 PM #16
      For a boosted application, would there be a benefit to adding a box on the plenum to increase volume (42mm intake with box added to back side toward firewall)

    17. Member Road Boss's Avatar
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      04-03-2012 03:18 PM #17
      Quote Originally Posted by lnoriel View Post
      I had read an article awhile back in European Car that highlighted a Eurosport modified 16V. In the article, they had ExtrudeHoned a 42mm US spec intake manifold and said it had better flow characteristics after the internal treatment than the Euro 50mm in its stock form. Of course, ExtrudeHone is the pinnacle of fluid dynamics in terms of internal porting & Polishing. I'm sure the same treatment on a 50mm would truly be awesome for a normally aspirated motor.

      I'm no expert in forced induction, but I would imagine that if high intake manifold pressures are your goal, then the smaller bore 42mm intake manifold would probably better suit your application.
      Interesting...I'm looking to stay N/A and just want to get the best out of my 16v. It is so hard to find a scirocco 50mm intake too. I'm also thinking about adding a 3'' mustang throttle body too.

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      04-16-2012 10:50 AM #18
      it's awesome to see people still messin with these motors!!

      some of ya's might remember "the beast"...

      ill post some pics and dynmo charts about this..ive dynoed back to back 42mm vw 50mm..along with a customer made short runner i made..results were suprising..

      this wa son a fully built top and bottom.

      im currently working on a new setup with and new but old intake setup CALLIN POWERDUBS!!

    19. Member danderso's Avatar
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      04-16-2012 11:40 AM #19
      ^ post that shtuff!
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