5th-Generation Maxima Y-pipe and Cat installation

Maxima Y-pipe and cat installation

By: beancooker

1. Remove all heat shields (10mm wrench).

2. Remove O2 sensors.

3.Spray penetrating oil on all bolts to be taken out. YOU WILL NEED A PIVOTING ADAPTER FOR YOUR SOCKET WRENCH. Remove 3 bolts on front bank, 3 bolts on rear bank and 2 bolts on cat. 14mm wrench Remove hanger 12mm wrench.

4. When all bolts are removed, take a 2×4 block and hold it to the body of car directly beside stock y-pipe at the rear bank. Take a 2 foot pry bar and put bar on top of stock y-pipe and under 2×4 block. Lift up on pry bar (with a lot of force) and stock y-pipe will pop out.

This is the stocker removed!

5.Put crush gaskets on new Y-pipe. Put rear bank up and use 1 bolt to hold rear in place. Front will need some convincing to go in. The flange will rest against the front bank down pipe. Tap (convince) with a hammer until protruding flange pops into down tube.

6. Replace 3 front bolts and 3 rear bolts.
NOTE. There is a shield between the oil pan and the new location of the front O2 sensor. Remove this shield (it won’t be used) and put bolts back in holes.

7. Replace O2 sensors.

See how California emissions have a lot of O2 sensors:

8. Put new cat in place and put gaskets where they should go. Bolt tight. Put new hanger in place.

9. Start car and check for exhaust leaks. If God graces you, as He did me, you’ll have none. Shut off car and remove from jackstands.

10. Pull car outside and start. Let run for about 10 minutes and listen for leaks. (swelling and shrinking of fresh pipes can cause a leak if everything’s not perfect. If you have leaks, fix them.

11. ENJOY!!!

Summary.
The horsepower gains are totally worth it. I don’t butt dyno any mods, but there are noticable gains. The gains are from 2500RPM and up. I think I lost a little power off the line.

I used a Warpspeed Y-pipe and Magnaflow cat. The Warpspeed Y-pipe is only 60% the cost of a Cattman Y-pipe and are exactly the same. I compared it with a Cattman at a local shop.

If you’ve already replaced your muffler (like me) you’re screwed. There are no “bees in a can” sound, but with a Magnaflow performer XL muffler the throaty V-8 sound goes away. I’m embarrassed/humiliated/ashamed to say, but my poor Max sounds like a Civic with a fart can. It’s loud as hell and has that annoying pop to the sound. However it is faster and that’s what I wanted, so I guess I can deal with it for now.

NOTE:The rear bank precat can be replaced with a straight pipe and you’re fine. If you replace the front bank precat with a straight pipe you’ll throw a code. If you “rod out” the catalyst in the front bank precat, you’ll throw a code. The good news, the precats flow at 450 CFM. The high flow cat I put on the car only flows at 700 CFM so unequal backpressure should not be an issue. Most of the backpressure encountered will be at rear cat, and at 700 CFM, I’ll probably have to do a few more mods to push that much exhaust.