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PostPosted: Wed Apr 17, 2002 5:14 pm 
As soon as I get a chance, I'm going to put on my "Dutra Duals". However, I'm starting to have second thoughts now about whether I want dual pipes out the back, or if I want the muffler shop to have them "gracefully" flow into one big (2.25) single pipe. I'm not that concerned about image, and I'm wondering if one pipe wouldn't be just as good for a mostly stock daily driver slant. Hmmm...
Let me know what ya'll's opinions are!
Thanks, thanks, thanks, thanks!

wes.moeller@compaq.com


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PostPosted: Fri Apr 19, 2002 11:27 am 
(User Above) wrote:
: I'm starting to have second thoughts now about whether I want dual pipes out the back, or if I want the muffler shop to have them
: "gracefully" flow into one big (2.25) single pipe. I'm wondering if one pipe wouldn't be just as good for a mostly stock daily
: driver slant.


Two 2 inch pipes would appear to have more area, and more flow than a single 2.25 inch pipe, but looks are deceiving. Because of the boundary effects on flow, the area next to the pipe doesn't flow much. Most of the flow occurs in the center of the exhaust pipe. The "center" of the 2.25 inch pipe is about the same size as the two "center" areas in dual 2 inch pipes. A 2.5 inch exhaust is almost as good as dual 2.25 inch pipes and better than dual 2 inchers.

One objective for exhaust pipes is to avoid bends, kinks, and dimples. If it is easier to route one larger pipe, do it. Conversely, if the large pipe requires contortions to get around the transmission or over the rear axle, use two smaller ones.

You can avoid the rear axle by coming out the side just ahead of the rear wheel on the driver's side. That saves some bends and a few feet of pipe.


dwordinger@earthlink.net


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PostPosted: Fri Apr 19, 2002 11:52 am 
(User Above) wrote:
: Two 2 inch pipes would appear to have more
: area, and more flow than a single 2.25 inch
: pipe, but looks are deceiving. Because of
: the boundary effects on flow, the area next
: to the pipe doesn't flow much. Most of the
: flow occurs in the center of the exhaust
: pipe. The "center" of the 2.25
: inch pipe is about the same size as the two
: "center" areas in dual 2 inch
: pipes. A 2.5 inch exhaust is almost as good
: as dual 2.25 inch pipes and better than dual
: 2 inchers.
:
: One objective for exhaust pipes is to avoid
: bends, kinks, and dimples. If it is easier
: to route one larger pipe, do it. Conversely,
: if the large pipe requires contortions to
: get around the transmission or over the rear
: axle, use two smaller ones.
:
: You can avoid the rear axle by coming out the
: side just ahead of the rear wheel on the
: driver's side. That saves some bends and a
: few feet of pipe.


In addition to the great tips listed above, you can do a 2 into one "collector" which can create some negative pressure in the other pipe, helping to "scavenge" the cylinders. The key is to have the primary pipes end inside a collector, right next to one & other, on the same plane.

I have done a few 2 into 1 setups that are quiet, have good low speed throttle response and mid range power, just what you want for the street.

Some additional info. came up when I searched for key words dual exhaust system (all key words)
Here is one post:
<A HREF="http://www.slantsix.org/cgi-bin/webbbs_config.pl?read=5778">http://www.slantsix.org/cgi-bin/webbbs_config.pl?read=5778</A>
DD


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