...just look at the volume taken up by a non-mandrel bend. It is huge. Measure circumferences, then calculate radius differences. The use Circ=2pi+*r. Then use area=pi*r(sqared) to see the volume differences. (a 2% radius difference maens you only flow 96%, and non-mandrel bends crimp out about 10%, so you flow only 81%). (I am home sick, so if my numbers are slightly off, forgive me).

The only way to get around it is to use a 3 and 1/2 inch non-mandrel tube instead of the 2 and 1/2 inch mandrel bend tube. BUT, the non-mandrel bend tube catches air, interfering with laminar flow. Air turbulence decreases flow significantly. Mandrel bend minimizes interference with laminar flow. Even a 3 and 1/2 inch non-mandrel bend exhaust will have significant laminar flow issues. But you have a special exhaust manifold meant to decrease laminar flow issues, so you are kinda' screwing that up.

So, what does this mean? In my SiS with 200-225hp, not much. In your 300hp beast it means alot. For you, flow is everything. Why get a custom exhaust maifold, big turbo, a custom downpipe, fully worked heads, and a megasquirt if you are going to stop up the exhaust(thereby screwing up back pressure and spooling up)? Given the $ you have invested, I would not pinch pennies in this area. Given the matched exhaust manifold you had crafted for $1000, I would have thought that you would be the last person to ask this question.

My humble 2 cents. My problem is I am great with concepts, but I have not drag raced in years. Back then I just ran open headers with a pair of bypass ports on my GTO when I raced it. I look forward to seeing what the other guys with practical experience have to offer.

• Mandrel bends necessary?, GM, Fri, 22 Sep 2006 05:50:54
  • I know it's not really related but. Saab has always use, SAABOOST, Mon, 25 Sep 2006 13:15:37
  • Re: Mandrel bends necessary?, MTAERO , Fri, 22 Sep 2006 21:31:24
    • Interesting link, Ben S, Sat, 23 Sep 2006 05:43:56
  • thanks everyone :), GM, Fri, 22 Sep 2006 21:25:01
  • Well, hiding in the last sentence. I guess your right., Chaz, Fri, 22 Sep 2006 12:42:16
  • For $150, I wouldn't skimp and crimp!, RBatsch, Fri, 22 Sep 2006 11:34:23
  • Re: Mandrel bends necessary?, Simon S, Fri, 22 Sep 2006 11:07:14
  • The guy is wrong..., Chaz, Fri, 22 Sep 2006 10:15:56 <-- Viewing This Message
    • let me clarify....., GM, Fri, 22 Sep 2006 10:45:16
      • That is a big clirification. Why didn't you say so?, Chaz, Fri, 22 Sep 2006 10:52:02
        • I did actually...., GM, Fri, 22 Sep 2006 12:13:23
          • Re: I did actually...., lms, Fri, 22 Sep 2006 15:38:08
            • Ive logged data with a tech2, jak , Fri, 22 Sep 2006 19:09:21
              • Go Mandrel, DJ, Fri, 22 Sep 2006 20:16:25

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