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March 2004
STRAIGHT THROUGH AND WIDE OPEN
MagnaFlow Installs Their Cat-Back System
Onto A 2003 Expedition
Photos and Text by Marshall Spiegel
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 Recently, I was standing around listening to a bunch of "would-be" car guys talking about exhaust systems. I was surprised when I realized that few in that assemblage really understood the difference between "press-bent" and "mandrel-bent" pipes. Of course, that made me review just what I knew about it. The way I understood it and simply put, press-bent exhaust piping results in pipes that are somewhat "pinched" where they bend and change direction. Pinched exhaust piping causes restricted airflow. Mandrel-bent pipes are bent with special equipment by which the pipes maintain the same diameter throughout, thereby assuring unrestricted airflow. Press-bent systems are cheaper, quicker and easier to manufacture and, for these reasons, are the obvious choice of vehicle manufacturers. On the other hand, mandrel-bent systems provide unrestricted airflow and considerably better performance.
To see just what a quality mandrel-bent cat-back (from the catalytic converter back) exhaust system is all about; how it is installed and what it does to a vehicle's performance, we visited Magnaflow Performance, a leading exhaust system manufacturer in Rancho Santa Margarita, California. There we photographed the removal of the stock system on a '03 Ford Expedition equipped with a 5.4 L V-8; a comparison of the stock press-bent system and Magnaflow's stainless steel mandrel-bent cat-back system; the installation of the Magnaflow system and dynamometer performance results before and after the installation. For the rest of the cat-back exhaust story, check out the photos and the dynamometer readout.
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1) Before the MagnaFlow crew touches the exhaust system, the '03 Expedition visits the company's dynamometer so the stock performance stats can be recorded.
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2) Ford has done a creditable job of "shoe-horning" their press-bent system in place with just a few restrictive "pinches" in their piping. That's a sizeable feat for a V-8 engine in a mid-size vehicle.
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3) Because the Expedition for 2003 is the first with four-wheel independent suspension, both the stock and the Magnaflow systems are brand new.
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4) The stock muffler, considerably larger than the Magnaflow unit, does not provide a wide open flow of unrestricted air. Factory designers are more interested in making the exhaust quiet for SUVs.
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5) To remove the stock system, the Magnaflow technician had to saw the pipe just behind the muffler.
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6) The section of cut exhaust pipe behind the muffler is routed over the right rear wheel independent suspension.
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7) Maneuvering the section of cut pipe out of the independent suspension so it can be discarded ain't easy
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8) The stock muffler is loosened from the forward section of exhaust pipe.
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9) With the help of an extension jack and a muffler "cradle," the stock muffler is removed.
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10) The Magnaflow mandrel-bent stainless steel cat-back system with the more compact wide-open muffler (top) is considerably better looking than the stock system, and not only adds more power but a nice throaty sound as well.
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11) The Magnaflow muffler is set in place and tightened up.
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12) The Magnaflow exhaust piping is maneuvered over the right rear independent suspension with barely enough clearance to prevent rattles.
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