Y-Pipe "Quiet Flex" Prototype #2
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.
Two Piece Design.jpg (214629 bytes) The second prototype Cattman Stainless Steel pipe design substituted a small piece of stainless steel flex pipe for the rear slip joint.  The use of a flex pipe helps greatly to isolate engine vibrations and prevent them from traveling down the entire length of the exhaust during hard acceleration.  The front slip joint remains.  The slip joint is extremely precise and requires no welding or clamping to hold it in place. 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.
Forward Section.jpg (185589 bytes) Front Slip Joint.jpg (231321 bytes) Rear Flex Joint (1).jpg (205713 bytes) Rear Flex Joint (2).jpg (226176 bytes)
Front Flange and O2 Port.jpg (215704 bytes) Collector.jpg (189563 bytes) Y-Pipe_rear_manifold_connection.jpg (154332 bytes) Whole Pipe.jpg (213343 bytes)
The above pictures show all of the pieces up close, and finally the whole pipe assembled together as it will go on the car.  The slip joint is 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.
Stock Y-Pipe at Pre-Cat.jpg (111722 bytes)

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. 

Flange Bolts & Nuts.jpg (95677 bytes) I chose to replace the pre-cat bolts and the rear manifold nuts, since the stock ones were a little rusty, and this was the second time the stock pipe was coming off.  While this is not entirely necessary, it is certainly not a bad idea - and it will make you feel good.  It was necessary to purchase the nuts to secure the Y-Pipe to the forward pre-cat.  The stock Y-Pipe has the nuts welded to it, while the Cattman pipe does not.  We used stainless steel lock washers to make sure everything was tight.
Here is the stock Y-Pipe removed from the car, compared to the Cattman pipe.  The rear pre-cat is clearly visible as a bulge just aft of the front tube.  The Cattman pipe is a much cleaner design, as it is essentially a straight-through pipe with no pre-cats. Stock Y-Pipe Removed.jpg (155127 bytes) Whole Pipe.jpg (213343 bytes)
Y-Pipe at Pre-Cat Lineup.jpg (114078 bytes) One of the issues corrected with the second prototype was a slight adjustment to the forward flange angle.  You can see from this picture that the new design mates perfectly to the forward pre-cat with no gaps at all.  One minor change that my mechanic had to make was to replace the bottom most bolt with a longer one, since the flange on the Cattman pipe is a little thicker than stock.  The stock bolt was not long enough for the bottom hole.
Rear Manifold - O2 Sensor.jpg (197889 bytes) This shot simply shows the new pipe mated up to the rear exhaust manifold, and the O2 sensor.  The smooth bends in this pipe are really a work of art.
Rear Flex Joint at Cat.jpg (128343 bytes) The new Cattman pipe with flex joint fit perfectly to the stock catalytic converter.  The stock hanger is re-used, and supports the pipe at the converter.  We had to put a very small bend in the hanger to avoid a minor rattle that was occurring when the car was floored from a standstill.  I don't plan on beating on the car like this too often, but I had to explore the limits when I test drove it.  Bend hanger out of the way, and no more rattle.
Y-Pipe Bracket - Bent Down.jpg (116542 bytes) Originally, the bracket shown in this picture fit properly, but when the forward section of the prototype pipe was reworked, the alignment of the bracket holes with the car changed.  Our solution was to simply bend the bracket out of the way.  The Cattman pipe is so much lighter than the stock pipe without the heavy pre-cat and heat shields that extra support is really not necessary.  This pipe isn't going anywhere.  My suggestion to Brian Catts will be to simply eliminate this piece and save on the production costs.
Y-Pipe Complete.jpg (214653 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 any gain in noise output.  As I had originally guessed, the addition of this pipe to a totally bone stock Maxima exhaust does not increase the exhaust note at all, and the flex joint is perfect for eliminating vibrations.  This is a totally streetable setup.

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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