Courtesy B-Pipe Restriction Issue
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Courtesy B-Pipe  Performance Mods

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6/11/2000

Editor's note: The following is an analysis of what I consider to be a serious design flaw in the Courtesy B-Pipe.  Courtesy designed their pipe to be a universal fit both for Maximas with and without an O2 sensor behind the catalytic converter.  Unfortunately, for cars which do not have the O2 sensor, the Courtesy design is a poor compromise since its installation requires that a restrictive Nissan-made OEM extension piece (which is not on the car to begin with) be added between the B-Pipe and the catalytic converter.  The extension piece is only required to house the O2 sensor, and on cars which do not require it the sensor hole needs to be plugged and this extension piece inserted between the cat and the Courtesy pipe simply to make everything fit!

What Courtesy needs to do is design a longer single-piece version of their B-Pipe which fits 95-99 Maximas without the O2 sensor behind the cat.  Other than this one design flaw, the Courtesy B-Pipe is an outstanding piece of work.

Stock B-Pipe at Cat.jpg (103793 bytes) This is what the stock B-Pipe/Cat junction looks like on a 1999 Maxima with California Emissions.  Note there is no O2 sensor behind the cat, and the pipe from the cat to the resonator is all one smooth, straight piece.  In fact, the entire B-Pipe is one piece all the way to the muffler.
p0000680.jpg (224000 bytes) Here is the OEM exhaust adapter which needs to be attached to the Courtesy B-Pipe on cars which do not have an O2 sensor behind the cat.  Courtesy supplies this part with the B-Pipe for owners who require it, but it is horribly restrictive, and seems to me would negate any performance improvements the B-Pipe provides.  Add to that, the O2 port needs to be plugged with a bung since it is not used in this application.
p0000672.jpg (234082 bytes) Give me a break, Courtesy  How about designing 2 different B-Pipes so this piece of crap isn't necessary?  The whole point is to improve performance and eliminate restrictions, then you give us this?!
p0000675.jpg (201588 bytes) This part cost me $30 from a Nissan dealer.  I bought it to satisfy my curiosity about this B-Pipe issue, and possibly to investigate cloning it in stainless steel.  This photo shows the end which attaches to the B-Pipe.
p0000676.jpg (219376 bytes) Side view.
p0000679.jpg (201417 bytes) This is the part that attaches to the catalytic converter.
CloseupExtension.jpg (121132 bytes) Here is a close up of the extension piece in place between the catalytic converter and the Courtesy B-Pipe.  
BPipeComplete1.jpg (122455 bytes) Here is the Courtesy B-Pipe.  Note the restrictive crimp (pic below) has been removed.  Very nice. 
Stock B-Pipe at Resonator.jpg (162846 bytes) The Courtesy B-Pipe eliminates this restrictive crimp behind the resonator on the stock exhaust.  The problem is that for cars without the O2 sensor behind the cat they are removing one restriction and then adding another (in my opinion, worse restriction) with the horrible OEM extension piece.

Solution - Courtesy, redesign your pipe and make two separate versions of it.