Best Cat-Back

[klonestar]

The only way you might get some positive increase in performance from a dual exhaust system with an inline six, would be to have a header with two seperate collectors that ran down to individual exhaust lines with some kind of crossover.

But dual exhausts off a single split would only garner you a lot of weird stares from most people. It might look cool, but you wouldn't get any increase in performance to speak of.

Depending on what rpm range you want to run you motor at, it would just be better to just increase your exhuast pipe diameter. Anything larger than 2.5" would be pointless, unless you planned on consitantly running greater than 5000 rpm. If you still want your low-end torque, 2.25"(stock) is plenty.

Thanks! Makes sense to me. Plus seems like more underneath to get banged up. Just wanted to check in case I was missing something.

Ken

 

[krakhedd]

My (stock) headers are 2 separate pieces with a collector. I think Clifford's dual outlet headers also come with an X-pipe, and this would be the best of both worlds.

I think you can fit a custom dual setup, but it's gonna have to sit right next to the gas tank. Maybe not the best idea, although I'm sure you could add some sort of heat diffuser/shield in there to help out. You'd want Mandrel-bent pipe as well though, and this could be a big problem in terms of cost. The best muffler shop around (the best work AND the best prices??? it seems mutually exclusive, but it's not) quoted me like $50 bucks for non-Mandrel custom exhaust (single), and something like $400 or $500 for including Mandrel bends. Nobody in the area has a Mandrel machine, so they'd have to get some Mandrel bends, and cut them together with straight pipe. This might turn into a summer project for me, if I can ever get off this damn night shift - my parents' neighbor, the dad of one of my best friends, is a master welder, and has welding equipment at his house. I'm sure he'd be willing to help me out in this endeavor.

The other problem with dual exhausts is you'll need 2 cats to pass inspection. More cost.....another $300-$400 I believe for 2 high-quality, high-flow cats.

If I got duals, I'd also go with 2.5" pipes. Should be plenty for a stock or stroked motor, but maybe somebody else can give a better recommendation for this?

For the record, I saw an XJ with dual pipes. As soon as I took a peek underneath and realized it was still 1 pipe with a Y, I thought what a poseur fag he was....that's some type of dumb shit usually reserved for ricers....

 

[ZomBrady]

. . . If I got duals, I'd also go with 2.5" pipes. Should be plenty for a stock or stroked motor, but maybe somebody else can give a better recommendation for this?. . . .

Dude, if you ran dual 2.5"s, well, that's the equivelent of one 3.5" exhaust! That's the size of exhuast piping that's found on those diesel pickups! Your best bet if you went with duals would be 2"s if your planning on building torque.

See, what happens when you enlarge the diameter too much for your intend application, the hot gases cool down and become denser. When this happens, and even though you opened up the exhuast, you start to lose exhuast velocity.

Why is this important you ask? Well modern camshafts have a certian amount of overlap built into them. This means that for a certain amount of time, both the exhuast and intake valves are open together for the same cylinder. This overlap on the exhuast side allows the a vacuum to form, which helps suck in the intake charge. If the overlap is on the intake side, it leaves a bit of exhuast gas in the cylinder gas in the cylinder, which decrease the combustion temperature(how's this work? you don't want to know) and reduces NOx emissions.

Okay, you've now master thermodynamics and cam design 101! Now back to why it's a bad idea to mess with pipe diameter. . . .

It really depends on what rpm range you want to run your motor in. If I were doing 5000+ rpm all day long, think about 2.5" dual exhuast. For a daily driver that operates at 3000 or less rpm, the very largest I would go would be a single 2.5" diameter pipe. Anymore than that and I would lose alot of low-end torque and Hp, not to mention mpg dropping too. If I had to have dual exhuast on a daily driver, it would be with 2.0" diameter piping. This would be close enough to 2.5" and just a bit more cross-sectional area. But I would still benefit from the increased balance of exhuast charges from the individual cylinders.

Now we're back to 'do I really need to do this? is it do I really want to do this because I really like screwing around?'

I KNOW which category I fall into!

My (stock) headers are 2 separate pieces with a collector. I think Clifford's dual outlet headers also come with an X-pipe, and this would be the best of both worlds.. .

And yeah! I've looked at and drooled over these! They're hella slick!

 

[krakhedd]

I had this argument with a guy on another thread around here not too long ago. I argued your point, he said the majority of torque tuning in the exhaust is made or broken in the headers, and in particular, the resonance. This has to do with the pulses of the exhaust, etc.

I argued EXACTLY the point you just made, and he said nope, wrong, and told me why.

I tend to believe him, for the simple fact that a good set of headers will improve your torque a very significant amount more than a cat-back exhaust. This, and the fact I'd like to believe him

Anyway, maybe I could go with smaller pipe, especially if I've got an X-pipe in there. And, an X-pipe helps with the exhaust pulses, so perhaps that's an argument for larger pipe after all....I dunno, I guess I'll cross that river when I come to it. Plus, I'm gonna be building a stroker soon - maybe I'll just leave the exhaust for when I'm done with that.

I also fall into that same category, by the way I usually end up breaking or blowing something up though. Blowing up/burning is a lot of fun though.

 

[williamk53]

I have rustys with the flowmaster 50, and had a glasspack before. There's no droning now and I can't hear it inside unless I get on it. Plus, it will last a lot longer than a turbo muffler.

How does it sound outside your rig?

 

[ZomBrady]

I had this argument with a guy on another thread around here not too long ago. I argued your point, he said the majority of torque tuning in the exhaust is made or broken in the headers, and in particular, the resonance. This has to do with the pulses of the exhaust, etc.

I argued EXACTLY the point you just made, and he said nope, wrong, and told me why.

I tend to believe him, for the simple fact that a good set of headers will improve your torque a very significant amount more than a cat-back exhaust. This, and the fact I'd like to believe him

Anyway, maybe I could go with smaller pipe, especially if I've got an X-pipe in there. And, an X-pipe helps with the exhaust pulses, so perhaps that's an argument for larger pipe after all....I dunno, I guess I'll cross that river when I come to it. Plus, I'm gonna be building a stroker soon - maybe I'll just leave the exhaust for when I'm done with that.

I also fall into that same category, by the way I usually end up breaking or blowing something up though. Blowing up/burning is a lot of fun though.

Ah, but this thread was about cat-back systems! If we're talking about making torque with the headers alone. . . Well, that's a different story!

BTW, he is right to a point, but really your performance then lies with your header and not your cat-back.

With shorter tubes, you build more high end Hp. While the opposite is true about longer tubes, which help you build more low end torque. And unequal length headers are the 'jack of all trades' headers, chich build hp and torque over the entire rpm band, don't have a set optimal rpm band.

You have to look at your exhuast as a complete system. The perfect exhuast IMO, would be a set up with long individual runners in the header, and a modest increase in exhuast piping diameter. This would be for building low end torque. If I where doing JeepSpeed, it would be short runners and a relatively large increase in exhuast piping diameter.

 

[SourApple]

i have a few tales to tell. i put on a gibson cat back on my 94 xj. as for the sound let me tell you i was dissapointed as all hell. picture a small boy who just had his puppy kicked.. that was me.. as soon as a drove it.. i have the 5 speed. i noticed a significant decrease in resistance in it when downshifting and the flow was indeed better... but the gibson had to go.. so then i went and bought a flowmaster 40 series for like 20% or 30% of what i paid for the gibson and used the flowmaster "original" 40 with my gibson tail pipe. that i like better... then my friend copied me with his 3.9 dakota and his 40 sounded better then mine... now i was back to the kicked puppy. so after my cat shit the bed and clogged up and i had absolutely no power.. i bought a magnaflow high flow cat... this + the 40 + gibson 2.5' tailpipe did me well.. it was loud and i was happy again ... then but i have to say my gibson tailpipe never really fit correctly plus there was no need for such a serious U bend in it for over the axlke with all my lift. so i cut it up and i made a side exhaust out of it with my high flow cat and my 40... and that now is not good enough sooo.. i went to a company called IMCO and i believe that they are located in Texas and i bought their "extreme" mufller it looks like a flowmaster but it is half the size and is only on chamber it is oretty much hollow except for a V inside that thing.. that is sitting in my room and is not yet installed .. im going to have a custom tail pipe made and i am going to buy headers and a head pipe...as well throw on the intake manifold froma 99 or newer with a big boy throttle body and this shoudl satisfy my sound needs..as for performance the gibson was all there.. just didnt fit well and why would u pay like 300 for that when u could buy a flowmaster and have a shop bend u a tail pipe all for prob 100 .. if you dont want the loud tone of the original 40 buy the delta flow it is nice a quiet but i highly recomend the high flow cat... world of a differece over my shot stock one... hope this helps someone..

Mike

 

[1987jeep]

I really like the dynomax, and it sounds great. Gave tons more low end torque but I also did a new catalytic converter.

 

[blue95xj]

i just made an $8 catback last night. it's a "hybrid" but works great and sounds great as well. this "hybrid" consists of a free flowmaster 40 series, a gibson cat back tailpipe (came with gibson when i bought it, couldn't stand the rice), some exhaust clamps, some welding, and a few hours of good hard work. i love my new flowson or gibmaster catback which ever you prefer and you can't beat it for $8.

 

[EZridaz]

I ended up going with the 2.5" Hooker Aero Chamber (fully welded/skid plate like FM)with a 2.5" Catco and header and sounds really good...nice low rumble...no interior noise...I was really debating between the Flowmaster DS 40,50 and SUV,the 70 series and the Dynomax Super Turbo and heard some sound clips and read thru a million post and debated to go a different route and not have everyone elses sound and glad I did...some of them sounded ricey or too loud and I didnt want interior noise/drone and it's rated to the same as an open pipe and flows 441cfm compared to Dynomax ST 360cfm or a Flowmaster 2 chamber at 357cfm

 

[blue95xj]

i too debated on the hooker aerochamber until a free 40 series popped up and i installed it the next day.

 

[Jposses]

but what you need¿?
sound or perfomance...
i used the tree cats borla, gibson and flowmaster...
for far the best is gibson loud sound and improve performance....now if you want more sound just get off the cat and thas right have a lot of sound¡¡¡¡¡¡¡¡

 

[raypla]

but what you need¿?
sound or perfomance...
i used the tree cats borla, gibson and flowmaster...
for far the best is gibson loud sound and improve performance....now if you want more sound just get off the cat and thas right have a lot of sound¡¡¡¡¡¡¡¡

What??

 

[CantonXJ]

What??

Was kinda hoping you were gonna translate that for us.

Does anyone else here speak gibberish?

 

[Cjmartz2k]

He's from Chile. How many other languages can you speak/type that well?

 

[Menzenski]

but what you need¿?
sound or perfomance...
i used the tree cats borla, gibson and flowmaster...
for far the best is gibson loud sound and improve performance....now if you want more sound just get off the cat and thas right have a lot of sound¡¡¡¡¡¡¡¡
2 Days Ago 21:05

What??

Translation:
But what are you looking for? A more pleasing sound or increased performance? I have used Borla, Gibson, and Flowmaster cat-back systems. I have found Gibson to be the best by far. The sound is better, and the performance is improved. If you want an even better sound, simply remove your catalytic converter and you'll have a very nice sound!!!!!

I think.

 

[CantonXJ]

He's from Chile. How many other languages can you speak/type that well?

Ich entschuldige mich, da ich nicht beachtete, daß er aus Chile bis kam, nachdem ich es bekanntgab.

 

[Jposses]

sorry my spanglishgermanglish........

but everybody understand the general idea?
welll...somebody can write well Spanish?
mmmm...........NOOOOO....
thanks Manbeu for the translation......

and gibson rules........

 

[streetpirate]

what about the cheapest, quietest, highest performance setup? keep it quiet and keep it a sleeper, then pull the cord on the Mr. Gasket exaust dump and have that nice pro-stock drag sound. (scares the piss out of ricers )

the problem with a loud car is that it atracts attention. not always the good kind. ( like the 'Po) and when i was just running a cat and no muffler, soccer moms would try to get me off of stoplights. a diesel dodge truck kicked my @$$ off of a stop light. and ricers kicked me on the highway.

 

[Silv2000XJ]

What can anybody tell me about the Rusty's Flowmaster kit? As far as how it sounds, HP increase, torque, etc. Thanks in advance!

-Dan