Ok so i think it's time to start thinking about adding a lil sumthing sumthing to my baby..

I wanna mod the exhaust as I got all intake mods and the headers... I thought Id start with the XLR8 cat... I'm sure that'll free up 5-8hp with my current conditions..

Has anyone figured out what gaskets to use? I hate the fact the XLR8 cat doesn't used the compression o ring gaskets.. those flat gaskets are much more likely to fail. ut still, what gasket(s) would I use?

Secondly I heard the O2 sensor in the cat will be super stretched and may need to be lengthened? is this tru? Is there any way to make it so i don't need to extend the o2... i hate cutting such crucial wires.

After I do the cat then I'd want to possibly add a high flow resonator, and then change the piping from it to the mufflers, but i'm worried about the sound, if i change the resonator.

Can I just change the piping from the resonator to the mufflers for better flow or is it pointless more or less?

your input is greatly appreciated

 

You should just email XLR8 for most of these answers...he knows best.

The cat is not that long, so i don't see how the O2 bung could be that much further away to make you have to cut wires. And i think that changing the long pipe from cat-->resonator would be more beneficial than just the tiny pipe from the Y split to the mufflers. If you don't want the sound to change then get a longer resonator...maybe 18" or more??

If you're really worried about sound, then do the cat and see how you like the sound then.

 

Plug & play. Nothing extra is needed other then gaskets & those are cheap & don't fail given the big ass flanges.
Sound will change. You may or may not like it. I really don't like it on mine. It made it louder overall at all RPM's with a drone at lower RPM's.
It's not going to be a big difference power wise. I didn't buy mine for gains & didn't really notice much. It revs a bit faster.
IMHO buy a set of mufflers to add a better look & sound & call it a day.

 

Ya i don't think you'll see 5-8hp from just a cat. Maybe from a full exhaust. I know a guy who may be getting rid of his exhaust...will keep you posted.

Are you more interested in performance or do you want more sound??

 

performance1st sound2nd... I like it the way it is.... i do want it louder however, but not if it's gonna be drone that will be inside the cabin when I am on my daily commutes.... I love the sound of the car the way it is. quite when i am driving normally.. and loud when i GIVER..

But if the CAT adds drone then u'd think it's making a real difference if just that can chane the exhaust note!?!?

Fuzzy02CLS
do you have stock exhaust and resonator still?

the cat itself added drone????
if that is the case I probably won't buy it since I do lots of highway driving and rpms are at 2100 all the time which is where the drone will be. damnit.

I really would like to do SOMETHING to the exhaust, and I'd prefer to not do the mufflers as my car will no longer be a sleeper.

but IF i ever come across some used comptech's i will POUNCE on them.

 

yes this cat will add drone. after i installed it with my b-pipe my car sounded ricey until i added a magnaflow resonator a few days later. theres still drone but its not bad its a low tone not really noticeable.

 

so you think i should be fine... considering i got the stock exhaust system from the cat on.?

I just don't want nothing major to change

 

Stock b pipe, stock resonator, CT mufflers, & headers. No drone(or very little) with stock cat. Loud at all RPM's, loud drone at low RPM's with addition of the cat.
I can;t do much about it now. I'm not spending more $, I'll live with it. It does sound great in a tunnel or driving under over passes

 

Just get a resonator. Mine cost me like $100 shipped next day to me and it got rid of the loud sound. Mine used to loud as he'll at all rpms.

 

lol... k so i should b just fine with the new cat..

fuzzy... what gaskets are u using on that?.. since xlr8 doesn't supply them to my knowledge

 

I have no idea. Shop installed it. I would think they are just regular exhaust gaskets like any car just sized up. Or they may even used gasket sealer.

 

I'm really surprised the cat would add drone to any system. Drone is caused by low speed exhaust resonance. The drone goes away as the exhaust speeds up, i.e. higher revs, floor the car. Installing a high flow cat, although it may increase exhaust note, will generally decrease drone. Now if you guys are missing resonators or mid mufflers, etc then that will cause drone issues. Installing a resonator in the system will help decrease that drone.

Although no one has dynoed the cat it should easily add 5-8whp. The stock cat is very restrictive: small piping and high cell count. The XLR8 cat is 300 cell and has 2.5" piping.

 

a modified jeep manifold gasket for the front one on mine (2 of the bolt holes had to be repunched, but works great otherwise)
now the rear one is just a universial 2.5 inch (i think that's the size) 3-bolt gasket, but it cracked on me (i proable overtightened, with it being a more fragile design/type) for some reason within two weeks or so, so i just used some RTV hi-temp sealent on it, and it's been good for the last couple of weeks

WHY???

and it actually raised the point of the drone on mine to 2000-3000, where before it was like 1500-2500
also it does make the exhaust louder due to it being less restrictive (what happens when you put on a less restrictive muffler)





also you need a o2 fixer on it too, my light just popped on this mourning (i was actually looking right at it when it popped on, so i know exactly were it turned on, and what i was doing) for a P0420 for catalyst efficiecy below threshold (but it was the first time it popped on within the last 6 weeks or so it has been installed

 

I said it would increase exhaust note.

It's not uncommon for a high flow cat to trigger a P0420 code - Cat Efficiency Below Threshold. The factory cat is very restrictive and the ECU has stringent parameters for oxygen content. A high flow cat is not filtering emissions like the original cat so that code can come about. It can be eliminated by installing an O2 spacer, what ppl call a "defouler".

http://store.excelerateperformance.c.../i-149537.aspx

That's an example of one but you can make them yourself with a part from Autozone, part # 42009

 

wait a second... our exhaust piping is 2.25" so how can the XLR8 cat be 2.5 inlet and outlet? technically the 2.5 outlet meets up with the exhaust which is 2.25. 1/4 inch less.

So technically it will is not getting rid of the bottle neck effect?

can someone plz enlighten me?

if this is so.. then technically u'd need 2.5" piping to make it worth while correct?

 

I've enlarged the flange holes to accomodate factory mid pipes or aftermarket mid pipes.

 

i wasn't talking about the flange holes I was talking about the actual piping of the cat in comparison to the exhaust piping which is 2.25inches

so technically there will be a 1/4 inch overlap if I bolt it onto my stock exhaust piping correct?

 

i know, just have not put one in yet , maybe you should also tell people that they might need one also on your site

also i am going to proably prefer an angle one anyways, just so it is not sticking out there like a sore thumb underneth

the cat tubing is still larger then even my comptech headers, and my apexi exhaust, but the main thing for the cat flowing better, is that there is less of the "CAT" material inside of it, to not be as restrictive as a stock cat, while still keeping the computer happy (supposedly, still need a defouler though, but it does take the smell that you get from just a test pipe away though)

 

yea i got the Comptech usa headers right now and all intake mods done and pulley too and I just KNOW i am losing MAD top end due to the HUGE bottle neck effect at the cat. i am just worried about the front gasket.. as I have been told to use gasket maker silicone... I don't like nor trust that crap for longevity, and i HATE HATE HATE doing anything 2xs. I had exhaust leaks from my last car and I want to BLOW the thing up.

I would like to get the cat for flow and for sound.. so I think i may just get it and then go hunting for another car's gasket that will fit. this is one mod I am not gonna rush I guess.... damnit. lol

i guess i'll just have to Do it myself.

Excelerate Can you get a gasket fabed up for us or what?

 

ummm...... read above ^^, i used a jeep's gasket ( can't be more specific, but i think it was the 4.0 manifold gasket, guessing though, but i know it was a jeep)(went to the exhaust shop with the cat, and asked for one to match it, the stock one the main hole was too small) just had to repunch 2 of the 3 bolt holes, with a hole punch (they just had to be moved closer together a little), and the 3rd hole was perfect, along with the main hole (which was more then large enough)(and it still has plenty of gasket around the main hole to seal properly even after i repunched those two holes


then the back is just a universial 3-bolt one, so nothing special there

 

The rear gasket is just going to be a 3 bolt 2.5" gasket with equi-distant holes. The front gasket is more difficult since it has more of an oblong shape. I'll get pricing again but it was fairly pricey last time I checked.