It seems like the thing to do nowadays.
I am planning to gut my pre-cats this weekend. One of the two is bad for sure as I can hear rattling. The question is by how much does the sound change? I want to hear from someone who has done it. Is there a drone at highway speeds? Anyone regret gutting their precat because it sounds so raw?

 

really?

Let's see how this flies for now...

If you have do not have any other exhaust modification, you will not notice much if anything in the sound department. I had headers with stock exhaust for years and never noticed anything different in sound albeit a slight bit of tone.

So please, give details on your car, modifications, etc.

 

I am also putting installing a y-pipe. my stock flex section is coming apart. I do have a resonated test pipe off ebay. Y-pipe is unknown brand. I have a 2001 SE.
So it will be stock exhaust manifold + gutted precats + y-pipe + resonated test pipe + stock muffler.

 

It wont be loud nor drone. I had a similar set-up on my 3.5L (headers/test pipe/Cattman B/stock muffler) and it sounded fine, no highway drone.

It's when you get a 3" exhaust is when things get loud, and of course it also depends a lot on how you finish it (muffler size and style) when not going 3".

 

did you notice power gains and mpg improvement?

 

The factory muffler will silence the noise. I have header and test pipe with 2-1/2" exhaust in my Honda and not much in sound change, but it's very loud with racing muffler.

 

if you gut your cats/pre cats or put in test pipes then your exhaust may get a bit raspy, it may not if you have a nice resonator in there. What it will almost always do is give your exhaust that popping noise as you decelerate. If you have a full exhaust the noise will be amplified and you WILL notice the backfiring.

Unless you are boosted/blown you wont notice a power difference. It will slightly free up the exhaust but not enough to notice without having F/I.

That being said, im happy i put a test pipe in, makes the car sound a little better I think hah. As for emissions? Im from florida so... no emission laws haha

Edit: stock exhaust, you shouldnt hear or feel a difference. If anything, itll be raspier

 

I do not support this post.

With my headers, power hell yes, MPG's, no clue.

 

I support your lack of support.

People keep using the word "rasp". I have to say, I'm getting a little tired of it. The whole thing is so-o subjective.

With gutted pre-cats, a cattman uneven y-pipe, OEM main cat, and cattman 2.5" cat-back, my exhaust sounds absolutely wonderful (to me). The tone is deep and consistently smooth. Much louder than stock (duh), but not at all like the continual drone of headers or a 3.0" setup.

Oops! There's another hackneyed phrase: "Drone". Sorry about that.

 

It is setlled then. I will gut both my precats, install the y-pipe and t-pipe. Hopefully I can get it done in one full day.
Got my cordless drill, chisels of various size, hammer. Wish me luck!

 

I've gutted my cats, 3" test pipe, and 3" exhaust with a 16" resonator...no rasping that I know of. Just that decelerating pop but it isn't loud enough to sound like a backfire pop.

 

Why not? Everything I wrote was from experience with my 4th gen. And from hearing other peoples 5th gens in person that have gutted cats or test pipes

 

Although very similar, the 4th gen is not the same as the 5.5 gen, most significantly in the pre cat area.

1.) Pre cats on both banks, vs 4th gen.
2.) We have proven that headers/gutted precats show a significant power increase on the 5.5 gen in NA form, reason being, refer to above.
3.) Sound is subjective, raspiness/drone, etc.

 

He's not denying you your experiences, nor your interpretation. It's your conclusions he doesn't agree with. Personally, "rasp" is in no way a term I'd use to describe my exhaust, and I have gutted pre-cats.

You might disagree. That's fine.

 

I assumed he had a 5th gen with the DEK motor, didnt think about the 5.5.

And yea the word rasp is very opinion based, i use that loosley

Rasp is an opinion oriented word yea. I agree with that hah

 

He does have an 01 .. maybe it's cali-spec.

Either way I'm a strong supporter of headers/gutted cats and 3" exhaust on any NA 3.0L or greater gen VQ.

 

Now ya'll got me thinking maybe I should go ahead and invest in headers. Everythings gonna be off the car anyway, might as well get it done now. Any suggestions on headers?

 

OBX or the Hotshots for sale in the FS section, rare item. Your choice. All depends on $$$.

 

been contimplating the same project (WarpSpeed Y pipe SS, Megan/Custom Test Pipe, Megan 2.5 CatBack)

Pics would be awesome

 

preach

 

im running all stock exhaust just with the muffler cut off and it sounds like a stock 350z i like it.

but after reading how much our stock y pipes slow us down i was thinkin about saving money and cutting the pre cats out and welding my own straight pipe to the cat. would they be worth doing?

 

I'm still learning an all, but i thought the Y-pipe eliminates the precat?

 

Not on your car.

2 exhaust manifolds (duh)
2 pre-cats
1 y-pipe
1 main cat

Aftermarket y-pipes have a more free-flow design than OEM. Cattman's is an uneven length design.

Headers eliminate the precats, not an aftermarket y-pipe.

 

Hm... 5.0gen Y-pipe WILL eliminate the pre-cats for Fed-spec and Bank1 for Cali-spec. 5.5 WILL NOT eliminate pre-cats. OP has 2001.

5th gen



5.5 gen

 

Hmm... blkfin35 has a 2002 Infiniti I35. He's the one who asked.

 

How much do the upper cats effect emissions?

 

Major for Cali but it depends what state you are in....

 

Finally got some time to tackle this job. Got the y-pipe off. 6 bolts off the manifolds came off easily. Man! Those 2 bolts on Catalytic converter are something else. Anyway here are some pics for comparison. I ended up cutting the bolts on cat. Now have to remove the back ones.
Cut with Dremel

My main cat looks to be intact. Since I'm putting in test pipe. Maybe sell it to junk yard for the Platinum.


This is the reason, why I'm replacing y-pipe. gutting bank 2 cat and test pipe is just might as well do 'em while I'm down there.


P.S(for those of you live in the upper midwest or the salt belt like I do, Don't attempt this!! Unless you like swearing and grunting with rusted out crumbling bolts.

 

i have a question. if i were to gut my precats as well, would i continually get the p0420 and p0430 codes all the time?

 

Yes, you would. You will need the O2 sims to get rid of those codes. Where did you get your y-pipe from?

 

You might and you might notm didnt get em with my 03 when I did it...and now my 02 with Headers only getting the heater codes no 420 or 430...some get it and some are lucky...

 

i gutted both my cats and i have no cel my exhaust sounds sexy

 

Gutting the front cat for those who wants to do it.



Chisel and hammer to break it apart




Breathe baby Breathe!

 

Got it from the classified section here. Unknown brand. On one of the flange it says Canada.

Went for 20 min drive, no CEL light yet. Sounds real nice. Seems more power at high end but that might be my manifestation. I'll get sound clip if anyone interested and curious about gutted cat, y-pipe, and test pipe set up sound.

 

Yeah i gutted out my firewall cat and i got the code but i am going to purchase the sim and get rid of it do you know if the 02 sensor can be reached from the top of the engine or the bottom of the engine

 

I'm Gonna gut my precats now, stock everything on the car. I will have to get the o2 Sims eventually.

 

Just gonna throw it out... Been using 18mm spark plug non-foulers for quite a while with no codes.

http://instagram.com/p/hUTeS-CKqD/
http://instagram.com/p/jFd7w7iKvj/
http://instagram.com/p/jFePGWCKv7/

 

Well, muffler shops won't do it, probably gonna have to do it myself or pay someone.

 

You gotta get a mechanic like Rochester's. He gutted his as soon as he asked.

 

Gutting them is not the hard part a hammer and screwdriver maby the lug wrench.its removing the rusty bolts that will take all the work.