It has been 48 hours since the Greddy SP cat-back exhaust & Warpspeed test pipe.
I already had the BudgetExhaust Y-pipe. Click Here for the review. I also have the Stillen Supercharger running 8 psi boost. The stock axle-back system is 2.25". My y-pipe, test pipe & cat-back is now a complete 2.5" system.

Warpspeed Test Pipe:
This basically replaced the catalytic converter. It is completely stainless steel & looks steel for it does not come painted. I got it for $35 shipped from http://www.warpspeedperformance.com
It came with the flanges, gaskets & new nuts & bolts. Good quality product! It did NOT increase noise levels & did NOT give any rotten eggs smell.

Greddy SP Cat-Back:
This is a 2 piece cat-back exhaust. It came professionally packed & looked very pretty with the greyish color paint on the pipe. The b-pipe had 2 good quality resonators welded on. This keeps the noise levels low.

My impressions:
Smell: Initially, the grease inside the exhaust will heat up and burn out. It will STINK like filthy rotten eggs. 3 hours later, the smell is gone.
Sound: I cannot hear my engine anymore. The exhaust is LOUD. For those looking for a stock sound, forget it. I've heard the Apex'i and it is the closest thing to stock sound. Greddy, however, isn't. To me, it will take some time getting used to it. It drones between 2500 & 3000 rpms and when you stomp on the gas pedal.
Power:
After the install, I drove around nice & slow, just testing everything out, making sure nothing falls apart, etc. The second time, it decided to push things a little...not too hard. Put the car in first, let off the clucth nice and easy and push the gas pedal. I felt like someone was pushing from behind. The car just wants to GO...GO...GO!! I stopped and tried it again, and oh boy does it move! And all this completely OFF the boost. You WILL feel the difference in horsepower whether you're boosted or not. I have quite a noticeable change across the powerband.

This gets even better. Now, I try & see this thing perform with BOOST. I launch nice & easy, with no wheel spin at all. At about 2500 rpms, I floor it and WHOA!...in first gear past 5000 rpms, and in second past 5500 rpms, my tires broke loose!. There is definitely more power now than before. I dyno this Saturday & will know the exact difference in wheel hp. Currently I am running stock tires & wheels. Time to put the 18's back on!

Cons:
The only negative thing I have to say about the Greddy is the noise. It sounds like a big V8 muscle car. A low frequency, subwoofer kinda sound...I dunno how to best describe it. You may like it but I am someone who likes a nice & quiet ride. I'll probably just get used to it. I'll try and take some video of my car this weekend & you can judge for yourself about the noise.

Many thanks to everyone on the .org, especially Jamie (Jay25) and Brian (BriGuyMax) for their help & advice. Listen to them. They know their stuff.

 

congrats Bobby.....now we just have to get you a new knock sensor!!!

 

Really happy for you!!!!: thats how your face was the day you floored it!!!

CAI is calling your name!!!thats a must!!!

when you get to it you will see and appreciate that nice whining noise!!!in the fenderwell, but it wont be louder then the V1 noise!!but will sound like you have something in there.

 

What I need right now are them 18" wheels with sticky Dunlop tires. Do they make ALL-SEASON (including snow) tires in 18"?! The power is way too much for the stock tires to handle. I just can't boost over 5K rpms in 1st or 2nd gears anymore. The tires break lose & get crazy wheel spin!

 

...and I thought that I will get lucky. I know BrianV and a couple others have had the P0420 Code after installing the Warpspeed Test Pipe. I got one last night. I reset the ECU this afternoon. Let's wait and see if it comes back.

Catalyst System Efficiency Below Threshold
Basically what it is saying is that there is that the Catalytic Converter does not have enough oxygen storage capacity. Guess what...there is no converter

Anyways, what are the options?
(1) Replace the O2 sensor on the intermediate (B-pipe). However, it would only be a matter of time before the new sensor recognizes that I don't have a freaking cat
(2) Ignore the Service Engine Soon light, and get crappy mpg
(3) Every couple of months, remove the sensor & clean it with some Carb cleaner to reduce the amount of deposits and make it think that I am running clean.
(4) Replace the stock cat and lose horsepower.
(5) Open to ideas.

PS: I also need to replace my knock sensor. The other code I have is P0325.

 

Gas Mileage: Since the test pipe & cat-back, My mileage seems to have significantly improved.
I zero my trip meter EVERY time I fill-up. After going through almost a full tank with the new exhaust setup, I read 371 miles before the low fuel light came on!!
I used to get such mileage BEFORE I was supercharged. After the SC, my average was 300/tank. The only other thing I've done is replace the knock sensor. Even that helps for the car isn't running as rich as it used to when the knock sensor was bad.

Maybe too early to jump to conclusions, but I'm hoping that this stays consistent!

 

just keep resetting the ECU. that's what i do. also, i heard the last O2 sensor is just for emissions. it should not effect performance or gas mileage. the first 2 sensors are more important for A/F ratio. with my exhaust i have found it to be quiet around 60mph. at higher cruising speeds it sounds as silent as stock. generally with only me inside it sounds mellow at all speeds, but put 3 additional people along with the AC and you have to modify your driving. just shift at 3k or more rpm all the time and don't get caught in a high gear on the beginning of a hill. double clutch downshift (or whatever you do) and keep those rpms up with a slight application on the throttle at all times when cruising and you'll see the drone is lessened dramatically. overall, you'll see the freeflow exhaust is satisfying.

 

Bobby with the engine light coming on that I cant really help you with, some guys their lights come on and others dont. I got my first engine light yesterday while on the highway with the other .org members and I thought it would be the 0420 code but I counted it and it was 0505 code , that just means the car is running fine keep on moving!! I know Matts said his light may come on once in a while but then he just resets it!!

 

The CEL came on once before. I reset the ECU. Yesterday, it came back on AGAIN! Same code P0420.
Actually my gas mileage has improved since the full catless axle back setup. My second tank delivered 350 miles. Not bad for a supercharged Maxima.

Maybe the ECU is leaning out a little due to the O2 sensor code. It is probably thinking that there is too much fuel to be cleaned & lean things out and add more Oxygen...I dunno.

I'm already getting used to the loud exhaust sound, maybe I'll get used to the CEL light also.

 

It sure is.
BTW, the recent MPG: 29.4 with 55% highway driving on your sig...Did you get that AFTER the free flowing exhaust?

 

Hey dashing max, so did you end up dynoing the car after the catback and test pipe?? Since you swear that you could feel the difference with a catback OFF THE BOOST, this is very good news!

 

Yes, I did. 267.7 fwhp. Initially, I was at 232.2 fwhp
I did the following since my initial dyno:
** 1 step colder plugs
** stock rims+tires (no 18's the second time)
** test pipe + cat-back
** new knock sensor (old one was shot)
Between better ignition timing, free flow exhaust, 5 lbs less unsprung weights from wheels & plugs, I gained +35.5 hp.

 

That's weird...

I have the S/S WSP Y-pipe, Catco Cat, and GReddy cat-back. Thing is totally silent. Even at WOT you can hear the engine itself over the exhaust. There's also no drone whatsoever.