STRAIGHT THROUGH AND WIDE OPEN
MagnaFlow Installs Their Cat-Back System Onto A 2003 Expedition

Photos and Text by Marshall Spiegel

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.

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.

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.

3) Because the Expedition for 2003 is the first with four-wheel independent suspension, both the stock and the Magnaflow systems are brand new.

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.

5) To remove the stock system, the Magnaflow technician had to saw the pipe just behind the muffler.

6) The section of cut exhaust pipe behind the muffler is routed over the right rear wheel independent suspension.

7) Maneuvering the section of cut pipe out of the independent suspension so it can be discarded ain't easy

8) The stock muffler is loosened from the forward section of exhaust pipe.

9) With the help of an extension jack and a muffler "cradle," the stock muffler is removed.

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.

11) The Magnaflow muffler is set in place and tightened up.

12) The Magnaflow exhaust piping is maneuvered over the right rear independent suspension with barely enough clearance to prevent rattles.