2003 6spd

I had the infamous precat rattle, my mechanic determined it was the rear one, after removing the y pipe out of the way i noticed the cat was not completely broken inside it was still intact but the material had separated from the inner housing, weird. Anyways its been gutted and the car feels more powerful and i dont notice any different sound, it sounds the same.

So do i gut the front precat aswell or not? Is there any problem if i dont? I read through the entire precat gutted thread 11 pages, and another 7 page thread aswell but no definitive answer on leaving juss 1 cat gutted

 

I would man, if not for equality between banks, atleast for the full power gains. Your already halfway there, it's only a few more bolts. Just remember that your gonna need to extend the o2 bungs or get sims.

I have bung extensions also known as spark plug anti fowlers (which I'm sure you know after reading that thread) and they have worked flawlessly, and were a lot easier to get than sims.
Good luck.

Oh and sorry for hijacking your clutch bleeding thread, I'm gonna start another one.

 

Gut it

 

Right on the money. This is exactly what is done to my car. Definitely gut it.

 

i honestly felt some power loss when it was rattling, now it feels like my car has more torque, really nice, i almost don't wanna touch it anymore cause its working! but i will get to it.

Ive looked around for the anti foulers, and ppl use the HELP foulers and stack 2 of them together.....what is the length of each fouler so i can buy just 1 fouler the correct size??

 

Gut them. That is where all the powers at on the 5.5

 

the hard part is done....gut the front and free up those ponies

 

I couldn't find the $10 anti-fowlers you mericans have so readily available, so I actually had pay $50 for o2 extensions from vibrant. They are actually really nice, they came with little pucks that have different sized hole in them that are held in place by a circlip, so you can adjust how much flow the sensor sees. I didn't put one in and just left it at the biggest opening and haven't a code since.

I'm not sure on the length but I'll measure tomorrow and let you know.

 

I was looking at gutting my pre-cat.. Was wondering how much of a sound difference it would make if any?

 

The rear is easy, the front one is a pain in the @$$.....

To the OP gut it, you will be happy you did so.....

 

So far my rear precat no sound difference at all, i was worried about this too, rochester had a post on 07/2011 that i found said he had more grunt and a slightly deeper tone which was pleasant

 

He even has a Vid on it....

 

I saw that video b4 and i dont hear anything except some whinning???
The rpms never even passed 1200 ??

 

You know, I started watching that video before I realized it was mine.

OP, I didn't gut mine, I had my mechanic do it. And IIRC, in one of them the substrate just falls right out, whereas the other one is a few hours of digging with an impact hammer and a chisel. My guess is the difficult one is the front.

I miss the sound of that car. Gutted pre-cats, into an uneven Cattman Y-pipe and the Cattman 2.5" cat-back, it was sweet. There are certainly more optimal exhaust setups (headers, 3.0" piping), but I surely did love the way that configuration sounded.

Good luck. Gut 'em both.

 

Just backing out of the garage. How fast should I have been going?

LOL

The whining was the idler pulley. Took me forever to figure that out.

 

It was called gutted precat video, i thought there would some serious revving i dunno

Well the video was not a total flop, i will be ordering those cool white cluster bulbs thanks to it, i bookmarked the video and named it "cool white cluster bulbs"

 

I did mine myself, and to be honest it wasn't that hard at all, and I am by no means an experienced mechanic. The hardest part is getting to the nuts and bolts that hold the precats onto the manifolds, if you take them both off you can gut them both in a half hour.

It's all about the right tools man, I bought a 12" long drill bit and chisel, drilled as many holes as I could, then smashed the chisel through it all, it was pretty easy.

Roc is right tho, the front is the harder one to do, because the bottom has a 90 degree bend, meaning no access from the bottom. You have to take it off.

 

There be a million videos of cars revving in park. Drive-by videos are so much more fun and realistic. Most all of the park & rev videos are pointless.

Here's my pointless Park & Rev video... ignore the walk up the driveway, I was playing with the camcorder.

 

So a few hours with the impact hammer and a chisel to the pre-cat.. Seems like alot of work but I'm a little worried about my 174k pre-cat so maybe its worth the few hours of labor.

 

Some heavy breathing 0:04 - 0:15. Steep driveway or what.

 

Very steep, Greg. But mostly I blame the out-of-shape, old dude holding the camcorder.

 

I like your foot dance at the end

 

OMG, it's like Tim "the tool man" Taylor's neighbor. You just never really get to see his face! BTW, I like the his and hers garages!!

 

Me too....

 

Seeing this old video again made me grab the camcorder and do a comparison. Man, do I miss the exhaust noise of my old car. This new one is WAY too silent.

 

Is there a specific anti-fouler that works better than others?

 

Ive looked around for the anti foulers, and ppl use the HELP foulers and stack 2 of them together.....what is the length of each fouler so i can buy just 1 fouler the correct size??

 

No one was willing to find the answer to my question

 

Sorry Man, I just plain gapped, I'll go check in a few. Just lemme wake up haha

 

ok so i have been waiting around for a few days and im starting to get worried and ive been TRYING not to make a new post about this so im just gonna say it here cause its killing me !!!!

my check engine light has NOT come on after 1 week of gutting the rear precat and 300 miles later. im actually worried cause everyone said its supposed to come on. so i reset the MPG calculator and im seeing 15.X MPG's and before i had like 17.X MPG's on the screen and im starting think im getting terrible MPG's???

even though it said 17.X MPG's in reality i would get 14.X MPG's because its all city traffic miles. but if the screen says 15.X then WTF am i really getting??

anywayz i just filled up on wednesday and started tracking my miles so i could fill up again and divide the miles by gallons just to make sure im getting the usual 14.X but in the meantime i see that number so low and its just killing me!!

do you think something is wrong after gutting the rear precat?? i do NOT have a non fouler or o2 simulator, theres no CEL. do you think the primary sensor b4 the precat got messed up during the gutting process causing bad MPG's?
do you think the post precat sensor got messed up? what can i do. or is the gutted precat performance so good that ive been driving more aggressive and therefore decreased MPG?

i dunno what to do or what to check. i have an OBD2 cable for my laptop so ima go fiddle with the sensor readings and see if anything is abnormal. any suggestions?

 

Disconnect the battery; drive easy for the the first tank of gas and let the fuel tables reset and stabilize

 

Just gutted both of my precats today as well as 2.5 piping with no resonator. Waiting for the o2 spacers and Ill be set.

 

If you use the HELP brand, its like 1 inch long. But since this is my second car that I gutted cats on. I instead ordered 2 longer version ones that are also stainless steel.

Heres the link

http://www.bigdaddiesgarage.com/straight-cel-fix.html

 

I took my precats off today aswell, the larger precat baffle just fell out when I disassembled it. Looks like I'll be gutting the smaller one tomorrow. My mechanic at nissan says the debris can actually flake away combusting back into the engine where it can do damage to the rings. I think this is why im doing an engine swap atm, my engine conked out 2 weeks ago (174k) due to bad rings. I know the rings that Nissan uses aren't the best to start with but I believe bad pre-cats just make them worse over time.

 

I forgot to metion, but on the larger precat. The baffle inside was already deteriorating, I wonder where the missing pieces went, In my engine probably.

 

That's really odd you didn't have your ses light turn on yet. Originally I had just my rear precat gutted as well without the O2 extender and my ses light turned after about 10 miles. The code I got was p0171- bank 1 running lean.

A couple days ago I got my O2 extender installed:


This erased my session light for P0171. However, after a few days I started getting P1148. Something about closed loop operation. From a search here it looks like it could be my bank 1 sensor 1 gone weird. I'll have to get my mechanic to check it out.

Cars is running great though. Just took a highway drive for the holidays to visit family for 300 miles and got 27 MPG with three passengers and a full trunk.

 

Today I was gutting the smaller precat with a chisel and hammer, I got about half way through and punctured a pretty decent size hole out the bottom. Looks like I'll be looking for another real soon.. Too bad they don't make straight pipes for the precat or some kinda flex pipe thats gutted already. This is defiantly not my thing here and Cattman headers are just too expensive.

I'm gonna check some junk yard's and see if I can find a cheap used one, otherwise I might try and get it off eBay.

 

Dont go by the computer calculate it like you said, and you should get better MPG if your precats were really clogged, as long as you are not heavy on the pedal, I gained MPG with doing the same on my 03, and gained MPG also on 02 with Headers.....

 

You should look into OBX Headers. They are not nearly as nice as Cattman but are much cheaper. Many people seem to have luck with them.
http://www.sparktecmotorsports.com/h...tm_content=pla

 

You just got to see if they have them in Stock, but are great to save a Nice Chunk of money....