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Discussion Starter #1
sorta new to this forum, but im curious. Anyone have any exhaust mods on their intrepid? i have a 97 ES...a couple of months ago i fabbed a length of exhaust pipe, ripped out the stock exhaust about 6 inches behind the 3rd cat, and installed it with a flowmaster 40 series muffler welded to the end. lovely.
i got to thinking though...what would two flowmasters look like under there? while i was under the car the other day (not on purpose, i dropped some money on the ground and it rolled under the car), i crawled further under it and thought to myself how hard it would be to make a true dual...however, i figure if im going that far, why not do it right. higher flowing catalytic converters? a larger diameter header? has anyone here attempted something like this? please, either give me more info or warn me before i get fined 10,000 bucks for tampering with emissions...tanx


oh yeah, if anyone has any questions about my exhaust, id be happy to oblige.
i like it, sounds great, and the car moves. I did a run a week ago in muggy, hot, maryland, and pulled a 15.53 @ 95 MPH. (with a .183 second reaction time YEAH!!)
 

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I don't know a damn thing about exhause except that 2 tips out the back look better than 1.

Questions:
What are the advantages/disadvantages of cat back vs. true dual?

Cat back means putting a "Y" pipe in after the cat converter and then running duals, right?

If you run true dual or cat back, do you need cats and mufflers for any reason besides emmisions?

What does the resonater do and do you need one if a cat back or true dual is installed?

From the factory, the muffler is the square object under the rear bench, and the resonater is the last item in the exhaust system (has the tips), right?

Sorry for all the questions but you said if anyone has any to ask. :D
 

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The difference between true duals w/ headers and the "whole nine" and just a cat-back system is in the application. If you are going to be using your car at the track more than you are for just gettin' around, then true duals would be the way to go.

Headers and true dual exhaust is better for higher revs. It drastically reduces the back pressure. The systems that are on our cars now are made to meet emissions and sound regulations and also for a plesant ride. They are made to optimize the performance within the guidelines of the those three.

Cat-back systems have been used for years on cars which, from the factory, have a catalytic converter. Basically what you are doing is removing the back-pressure created by the muffler & resonator, but leaving in the catalytic converter. This does produce a performance increase, although not as pronounced as a true-dual w/ headers.

The major downside to these is that as you reduce back-pressure you increase the release of un-burnt hydrocarbons out your tail-pipe. The purpose of the back-pressure is to limit how much of the exhaust gases actually get pushed out of the cylinders. There will always be some un-burnt gases in the cylinder. The back-pressure keeps more of these un-burnt gases in the cylinder for the next cycle, which decreases the emissions. Anything that you do to reduce the back-pressure will increase your emissions, which can get very costly if your state/city starts checking emissions.

Also, bottom end torque is also decreased by either of these systems. I really noticed this on my '70 Chevelle. When it came time to replace my 'Cherry Bombs', I replaced them with a set of Thrush mufflers which wheren't as free flowing and the bottom end torque increased, but the top-end decreased slightly. The effect of having less back pressure in a system is for increasing the engine's ability to breath at high revs. That is why you should select the setup for your application.

Mopar4U:
A cat-back system doesn't necessarily mean putting a "Y" behind the catalytic converter. It just means replacing the factory system in favor of a "free flowing" (less back-pressure) system. That's it. If you would like a dual setup out the back then you would need to split the exhaust at some point to do so. A dual outlet system could perform the same as a single outlet system. It just depends on the person making the system and what they want out of it.

The one purpose of the resonator was to decrease the sound of the exhaust. This setup is used to reduce the back pressure that a single muffler, at the same sound output, would create in the system.

If it is your intention to make a system that is as free flowing as possible then you should try to eliminate all bends in the exhaust tubing or make them sweeping bends. The headers should be equal length primaries that not be too big (some research into this would be a must). Too big and the exhaust gases will actually expand and slow down.

Some of the things that I have said in this post may be incorrect. I am just thinking out loud for the benefit of all. If something is incorrect and you know the answer please post. I hope this helps you all out in your exhaust mods.

Later
 

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Discussion Starter #5
swartlkk is right on the money. i have seen a drop of torque off the line. not a severe one, not one to really worry about. it certainly makes up for it once it passes 35 miles an hour, though. then she moves...and the shift from 2nd to 3rd at about 5500rpm (65 mph) sounds freaking awesome....
...you know what! screw that whole dual exhaust thing altogether...got a new idea...a buddy of mine's got this on his '70 olds 442...he calls it a "dump", i call it the "batsignal", cause every time he yanks it, crime fighters from miles around begin to hone in on the vehicle...(a dump is a modification that opens up the entire exhaust system directly behind the headers...really loud and really illegal)
i wonder how an intrepid would react to NO backpressure at all? my car was pretty loud on the lift right after i ripped out the exhaust...hmmm.....nevermind. :rolleyes:
 

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Kyle,
Thanks for the info. A few more questions.

I am just looking for the 2 tip appearance, performance is optional, sound would be a nice addition (as long as it doesn't sound like my John Deere 111 riding mower), and I don't have any emissions inspections where I live, so **** emissions as well. What should I do????? How about this: Remove the muffler and resonater. Place a "Y" after converter and place 2 free flowing mufflers at exit of car? Or would you remove the cat converter as well? Would you put 2 mufflers at the exit or just pipe and no mufflers?

Thanks for any advice
 

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What I plan on doing to my system consists of a high flow catalytic converter, two flowmaster mufflers, and four chrome tips. I just need to get the money together and get it all welded up. :D
 

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I remember a thread on MoparChat.com about an exhaust dump that came factory on some Stealth Twin Turbos. If I remember correctly these cars had two exhaust systems after the exhaust manifolds. One was for off the line then above a certain RPM this solenoid activated dump valve would open up to allow less back pressure at higher RPMs. The only problem was that it was around 400-500 bucks... It would be awesome however... You could have it controlled by rpm so you could have full off line torque and still open up the breathing at high revs. This could be done with the dump before the cat and run another pipe right along the other and out the back. On that pipe you would only want some very high flow muffler and I wouldn't even worry about the cat. If emissions testing comes about then just turn it off. That would be sweet. Especially when you blow some ricers doors off the line and watch them **** their pants when the valve opens up and you take off like a rocket. How awesome would that be...

Here is the pictures of bbull41s 98ES:
<A HREF="http://www.clarkson.edu/~swartlkk/trep/pics/bbull41s_98ES/crossover.jpg" TARGET=_blank>
Cross over pipe to reduce backpressure
</A>
<A HREF="http://www.clarkson.edu/~swartlkk/trep/pics/bbull41s_98ES/undercar.jpg" TARGET=_blank>
Under rear of car view of the exhaust system
</A>

He has completely removed the cat. It all depends on what you want to do. Personally I would only replace my cat with a high flow, such as a Magna-Flow, cat and some high flow mufflers. I don't have any money to do this right now but I will sooner or later.

If you want to see more pictures of bbull41s 98ES go to the Dodge Intrepid Yahoo!Group. You must be a member to view the pictures.
Click here to go there now.

Later

[ August 15, 2001: Message edited by: swartlkk ]
 

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Very impressive work done there, must sound a beauty!

[ August 15, 2001: Message edited by: Si ]
 

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Nissan had, maybe still does, a special muffler on some of their models. Sounded like a great idea and I often wondered why no one else did it. The muffler had a simple (?) spring loaded valve of some sort that remained closed during the lower end of the rpm range to aid low end torque and was also quieter. As rpm increased, the exhaust flow pushed against the valve, maybe a simple flapper valve, and allowed the exhaust to go through a less restrictive route to the tail pipe. See? Sounds way too simple ... so why don't others make something like that?
 

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My one question in all of this is "What third catalytic converter?" Is that a California thing? Mine had 2 cat's and then it came to one pipe that ran to muffler and then to resonator. If I remember right the 3.3 had the 2 pipes come together then it ran to one cat and then to the muffler then out the back with no resonator. Am I right or am I insane? Don't answer both please.
 

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The 1st Gen 3.5L's had three cats. There are small ones on each down pipe from the manifolds and then a large one right after the 'Y'. This is factory, however, with out knowing what someone might have done with your 'trep... It is quite possible that somewhere along the life line of your 'trep that someone decided that the ~200 bucks for a new cat was too much and just said get rid of it. There are much more restrictions now on what a muffler shop can do with these "emission legal" cars.

*sigh* guess I will just have to get out the saws-all and torch and do it myself... That is when I have the money to do it.

Good luck on your projects whatever they might be.
later
 

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Discussion Starter #13
i dunno about the whole permanent removal of any of the catalytic converters...here in maryland, someone told me that there was a huge fine for tampering with emmission control devices...like a $10,000 fine. maybee wrong, but i dont want to find outt the hard way, ya know?
 

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Discussion Starter #14
oh yeah, for those boy-racers in their
wal-mart performance hondas and acuras...i was thinking of installing a railroad style cow catcher on the front of my car.......hehehe
 

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Hey Swart that was a pretty cool link. You should tell this guy to come over here and join this BB, we got some questions for him. He has a similar setup to what I am designing. I would like to know what mufflers he got. How they sound and perform. And how in the hell did he get maderal bent custom made 1 7/8" pipes? (Assuming his are the same diameter as our 1st gens).

By the way I believe that the "H-Pipe" only helps on cars with a particular firing order. I know Mustangs(who are famous for H and X pipes) will fire down one side completely then the other which gives them that wild sound. The LS1 in the Camaro/Vette go back and forth, which produces more power but doesn't sound nearly as good.

Buschman
 
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