Y-Pipe Prototype # 1
This page Copyright June 07, 2003 , gregp@greghome.com 
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Cattman Stainless Steel Y-Pipe

[ Y-Pipe Prototype # 1 ] Y-Pipe "Quiet Flex" Prototype #2 ]


Shop Manual - Exhaust.jpg (279273 bytes) This is what the "Y"-Pipe looks like for the 1999 CA/NLEV Maxima.  The official name for this part is "Front Exhaust Tube Assembly".  Note it is a two-piece design which includes the forward pre-cat as a separate assembly.  Both the Stillen and Cattman replacement pipes for CA/NLEV vehicles do not eliminate the forward pre-cat, as they do on Federal Spec cars.  It stays in place exactly as-is and is necessary to maintain the car's OBD II compliance.  The rear-pre-cat, however, is removed completely from the aftermarket design.  The car will still pass emissions with flying colors, and will be a lot more powerful.  The mighty VQ30DE engine is dying to be unleashed, and will be once the stock pipe is replaced.
Forward Exhaust Manifold CA Emissions.jpg (145927 bytes) If the above illustration from the 1999 Shop Manual doesn't give you a feel for how the 1999/2000 CA/NLEV exhaust looks, this photo was taken standing directly in front of the car looking straight down at the forward exhaust manifold.  The blue wire leads to an oxygen sensor which is installed in the manifold.  The Federal Spec 4th-gen Maximas have the O2 sensor but it is not as visible as the CA models.  Also, the pre-cat is surrounded by a heat shield so you can't actually see it.  The Federal Spec vehicles do not have the heat shield, since the pre-cat is not attached directly to the exhaust manifold as it is in the '99/2K CA-spec.
Y-Pipe Crush Rings.jpg (162305 bytes) Here are the Nissan OEM gaskets necessary to install the Y-Pipe.  The large, flat gasket goes between the Y-Pipe and the catalytic converter.  The smaller crush ring gaskets are for the Y-Pipe connections to the rear exhaust manifold & forward pre-cat .  Note the crush rings are different for the CA-spec vehicle.  The smaller crush ring (top) is for the forward pipe section.  Nissan part numbers are visible on the bags.  Prices from Nissan were as follows: Small crush ring - $2.76, Large crush ring - $5.16, Cat gasket - $3.43.  Cattman normally supplies crush rings with their production pipes.  They do not supply a new cat gasket, which should probably be obtained from a dealer and replaced.
Y-Pipe - 3 sections.jpg (170747 bytes) The first prototype Cattman Stainless Steel pipe design utilized a three-piece system which was held together by a series of slip joints.  The joints are extremely precise and require no welding or clamping to hold them in place. Unlike the Stillen pipe and the stock Nissan unit, Cattman's original design eliminated the flex pipe in the aft section.  It was discovered later that this design, although ideal for a race-prepped Maxima, was not ideal for a street-driven car.  Once could argue that the Y-Pipe should not even be placed on a street car, and in fact it comes with such warnings, but the truth is that most people who have this mod are power enthusiasts who do not race.  The use of a flex pipe helps to isolate engine vibrations and prevent them from traveling down the entire length of the exhaust during hard acceleration.

I chose to go the extra step and have Cattman polish the pipe using a two-step process which results in a show-like finish.

Y-Pipe front flange.jpg (125994 bytes) Y-Pipe catalytic connection.jpg (172216 bytes) Y-Pipe rear manifold connection.jpg (154332 bytes) Y-Pipe assembled.jpg (156369 bytes)
The above pictures show each of the three pieces up close, and finally all three pieces assembled together as they will go on the car.  The slip joints are very precise and will be "gas-tight" without any welding, crimping, or sealing.

Below is a series of shots showing the stock Y-Pipe exhaust system before installation of the Cattman pipe.

Stock - Fwd manifold connection.jpg (104445 bytes) Stock - Catalytic connection.jpg (131856 bytes) Stock - Rear O2 sensor.jpg (125739 bytes) Stock - Entire Y-Pipe assembly.jpg (129236 bytes)
Before taking off the stock Y-Pipe, both the main 3-way catalytic converter heat shield and forward pre-cat heat shield must be removed. Remove Catalytic Heat shield.jpg (119957 bytes) Remove forward Heat Shield.jpg (106670 bytes)
Rear Manifold.jpg (127953 bytes) Three nuts must be removed from the rear exhaust manifold.  A universal joint is necessary to get at one of the harder to reach nuts, but it comes off no problem.
Forward Pre-Cat.jpg (109495 bytes) For the CA-spec 1999 and 2000 Maximas like mine, the forward pre-cat has to stay put or the Engine Control Unit ( ECU) will be very unhappy.  The front pre-cat needs to be loosened slightly at the forward exhaust manifold in order to get the stock Y-Pipe out.  It is a little tricky.  Note the forward O2 sensor embedded in the pre-cat.  This stays put as-is.

The stock Nissan Y-Pipe has the nuts built into it, so when you put the Cattman pipe on you have to screw on 3 of your own nuts to match the stock bolts.  The nuts required are 1.25 pitch, and can be purchased at any hardware store.  This picture shows the bolts already removed.  The three bolts go in from the opposite side of the picture.  

Pipe Comparison.jpg (142663 bytes) Here are the two pipes side by side.  The clean, smooth design of the Cattman exhaust flow compared to stock is easily apparent in this picture.
Front Sections.jpg (146143 bytes) Front pipe after slight mod.jpg (95887 bytes) Since my pipe was the first Cattman pipe ever built for a CA-spec '99/2K vehicle, part of what we were doing was checking the fitment of the piece to ensure quality in the production versions.  As you can see, the part of the Cattman pipe sticking out beyond the flange was a little bit too much, so we had to shorten it a bit.  No problem, since my shop had the tools necessary to do this.  Production versions of the pipe will obviously have the correction.  The second picture shows the forward part of the pipe after it was cut down such that only a very small portion stuck out beyond the flange - just enough to provide a spot for the crush ring gasket to seat itself.  Don't worry - you won't have to do this on your pipe!!
Front pipe connection.jpg (119994 bytes) This is not the best picture, but it shows the Cattman pipe connected to the forward pre-cat after the slight length adjustment was made.
Cattman pipe catalytic.jpg (134282 bytes) The Cattman pipe fit perfectly to the stock catalytic converter.  The stock hanger is re-used, and supports the pipe at the converter.  This is where Cattman's use of slip joints really comes in handy.  If the alignment is a little off, all you have to do is rotate the rear pipe within its sleeve to correct.  A perfect fit results every time.
Cattman pipe complete (1).jpg (135216 bytes) Here is the completed pipe, looking very happy in its new home.  There is a definite and noticeable power gain with this pipe, without much, if any, gain in noise output.  I have a Stillen muffler, which tends to drone a little bit in the 2200-2400 RPM range, but the addition of this pipe only changed the tone, and not the volume of the exhaust note.  I have a feeling that the addition of this pipe to a totally stock Maxima exhaust would result in virtually no noise gain at all, but this is just a guess.
Cattman pipe complete (2).jpg (146204 bytes) I was amazed at the quality and fitment of this pipe, especially considering it was a prototype.  I would like to thank Master Mechanic Joe, at Unorthodox Racing for being the true genius behind this install.  He made it look easy, although this job is not something I would recommend for an average do-it-yourselfer.  Thanks also to Brian Catts of Cattman Performance, for finally getting so sick of me bugging him for a stainless steel version of his Y-Pipe for my car, he had to go out and make one. 

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