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Gene
Dodge Dakota
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8/05/2003
23:43:09
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 Subject: want to gut or remove cat? read this!
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I have read some of the questions asked on this forum about gutting out a cat or removing it because a friend of mine said a lot of people were saying things about this procedure that are 100% wrong. They obviosly dont know what they are talking about. Like the recent post titled "line on cat", somebody replied that removing the cat can result in warped valves. That is the stupidist thing I have ever heard. There is no possibe way the removal of the catalytic converter can cause warped valves, and someone also said you could lose performance because it will result in less back pressure. That is also entirely false. Less back pressure will result in greater performance on a car cause it will get rid of the exaust faster. Back pressure is needed on a 2 stroke bike, not a car. Why do you think my Dodge Cummins has a stock 4" exaust pipe? I am a 5 star certified chrysler technition and have been for over 15 years, and half the people on this have absolutely no clue as to what they are talking about. I am not saying all is false, there are some really smart people on this site too. If you are thinking of gutting or removing your cat, it will result in less back pressure, increased exaust flow, and better performance.
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Gene
Dodge Dakota
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8/05/2003
23:50:18
|  RE: want to gut or remove cat? read this!
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Sorry, got a little tense there. I am not saying this site is stupid, there are a LOT of smart people on this site, it just makes me mad when people think they know what they are talking about but sont and give someone the complete wrong answer idea. I imagine the members area is better. I like this site a lot, not saying its bad, just some of the answers are.
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Rooster
Dodge Dakota
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8/06/2003
00:14:16
| RE: want to gut or remove cat? read this!
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Hey moron, I work for dodge and played a big part in setting all this up parts for the new mopar performance divsion. I am sorry to say but you don't know what your talkin about. Go to google and type "back pressure"
Maybe design your own motor after you go to college, lol.
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Joe
Dodge Dakota
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8/06/2003
00:15:46
| RE: want to gut or remove cat? read this!
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In a way it makes sense that you can lose power from cutting it. They say you need air moving in and out slower, yet under pressure to make the most of torque. But for max hp you want it in and out asap. I have heard you can mess up your valves somehow w/o backpressure. I knew this dude with a Z28 w/headers and straight pipe. When he tacked it out you could see flames. I dont know the truth to this.
Some people on here are having trouble with their brand new trucks being repaired correctly under warranty. Hopefully you can give them some words of wisdom since you work at a dealership.
If less backpressure meant more power, then I would think a lot of people would cut the cat and the muffler, but maybe not, since its not worth all the noise.
I also saw that Larry of JandJ suggested single in single out exhaust for max power since the single in dual out reduces backpressure, I dont know though, just a thought.
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Gene
Dodge Dakota
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8/06/2003
00:29:40
| RE: want to gut or remove cat? read this!
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Many people dont want to cut their cats or gut them cause if something went wrong, it is a lot for a ney one. I have put OEM cats on cars and they can be up to $400. So they could be hesitant. Also no cat means more pollution, and failed emmisions testing. Also check engine light can come on because the O2 reports that the cat is not working. My son Just got a Dynomax Single in Dual out Muffler on his 89 V6 3.9 and it has a tremendous increase in power, especially off the line. Also it sounds really good. It was 1 in 1 out before and with 1 in 2 out is has much more power.
Hey rooster, I work in the service area and have been certified for over 15 years. Dont tell me I dont know what I am talking about. I dont work in the sales department or some cheap garage and say I am a part of the mopar performance division. I probably know more about cars than you. You havent been Drag Racing pro-stock cars for 10 years. I think I know what makes a car perform.
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Rooster
Dodge Dakota
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8/06/2003
00:49:59
| RE: want to gut or remove cat? read this!
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let me put it this way, umm ANY engine will suck a lil air back through the exhaust after a high rev. W/O the cat the air it sucks back won't be as hot, (In other words, the cat heats the air". Now colder air on hot metal like surface will cause things to warp.
The larger the stroke to smaller bore the more air the motor will suck back through the exhaust.
Also remember that the hotter the motor the more air it will suck backwards. This is because the cylinder is hot and the air outside is cool so it sucks the cool air like the base of a fire....
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IntenseDak39
*GenIII*
8/06/2003
08:30:21
| RE: want to gut or remove cat? read this!
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all naturally aspirated engines need backpressure to work. Wether it be from just the exhaust ports, to all the way to the muffler. You have to find the medium between not enough and too much. The thing with no backpressure is that your exhaust velocity is too high and thats when you loose power. If the air is going out faster than the engine can suck it in, then what do you think is gonna happen? loose in torque mainly. Thats why people with low back pressure systems feel a lose in low-end torque. At the speed the pistons are moving, they cant pull in enough air to compensate for how much is leaving.
but i am not saying dont gut your cat... just dont have a straight pipe all the way back.
believe us if you want to.
1998 Regular Cab V6 Auto
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J and J Auto
Dodge Dakota
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8/06/2003
10:15:20
| RE: want to gut or remove cat? read this!
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Intence hit it right on the head.
In my case the way my motor is built a Cat is
just a cork in my system and I need the flow
No Cat
On a perfictly stock truck removing the cat will
cause a power loss on the low end take your
cat out and put a 3.0 exaust system on and your
truck will run like crap.
You can gut the cat and stay with a 2.5 in out single tail and your truck will have more low
end and not sacrifice on top.
I run no cat and a dynomax 11748 2.5 in out with
JBA's a 2.5 tail and I am stroked ported and
custom cam and it flows perfict, why would you
need to go bigger on a stock or near stock set up
You need to find what is right for your truck
Larry
J&J Auto
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Paul
Dodge Dakota
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8/06/2003
11:14:14
| RE: want to gut or remove cat? read this!
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Probably the best read on the effects of back-pressure that I've found...
http://home.tampabay.rr.com/redroby/3liter/exhaust.html
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IntenseDak39
*GenIII*
8/06/2003
16:56:37
| RE: want to gut or remove cat? read this!
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Good find Paul!
I have right now a 2.25" custom y-pipe going into to the stock 2.5" exhaust with a gutted catco cat. Then to a crappy flowtech terminator muffler that has lost its marbles. Right now i get a code P0420 if i drive on the highway a lot and go to city driving... but never did that before when i had my tail pipe... just to show you that the exhaust is moving to fast on my truck.
1998 Regular Cab V6 Auto
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J and J Auto
Dodge Dakota
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8/06/2003
20:22:47
| RE: want to gut or remove cat? read this!
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After removing my cat I get the 32 EGR code every
now and then and I know its not the EGR it is all
the other readings from O2 Map and IAT that are
causing the light. They are out of there
stock tables with less back pressure.
Not picking up the change when the EGR is suposed
to open, Big Deal
Besides that my EGR tube is blocked off, I don't
know about you but I see no advantage to shoving
hot exh into your intake and I guess so did mopar
they quit doing it in 96 and newer.
I run a custom 2.5 Y pipe into a 3.0 collector
that is about 14" long and drop to 2.5 at the
muff and a 2.5 factory tail no cat and JBA's
Stroked and ported, how could a stock 3.9 need
to be bigger when I am flowing this through a 2.5
muff and tail.
Take your y pipe off once and run open manifolds
and your motor will not rev up you need back presure
on any motor how much depends on what you have done
to it.
Larry
J&J Auto
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Dakota_Don
Dodge Dakota
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8/06/2003
22:05:42
| RE: want to gut or remove cat? read this!
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cutting out the cat, wont that harm the emissions and the computer/fuel system
make it run lean or rich????
fill me in, please???
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Banks
Dodge Dakota
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8/06/2003
23:02:37
| RE: want to gut or remove cat? read this!
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i have a 94 dak 3.9 and the converter started rattling so i had it removed. lot cheaper ($30 vs. 200). i have seen more power that way. Then a bout ssix months later i got a flomaster "the original flows" and it actually has even more low-end tq than before! the only thing i dont like about it is that it is kinda loud. i was going to a friends house and they said they could "hear me coming at the end of the road".
Banks
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da man
Dodge Dakota
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4/12/2004
22:53:59
| RE: want to gut or remove cat? read this!
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You all are talking about how bad taking the cat off is. And theres much talk about backpressure and how it can warp your valves. correction you cannot warp your valves unless you have the pipes coming out behind the doors it just wont happen. also if your so worried about that what you need to do is put a small glass pack on. no cat no muffler just straight pipe and the glass pack this will create enough backpressure so your first sensor will not go off, plus this way its also impossible to warp your valves. it'll still be loud but not as loud as strait pipes, plus if you installed headers on your truck your engine will be able to get rid of the exhaust fumes much faster and it wont suck in the cold air like some have said it'll do
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87dakota500
Dodge Dakota
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4/13/2004
12:23:40
| RE: want to gut or remove cat? read this!
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anyone know where i can get a high flow cat for my 87 dakota but not just the cat the hole pipe and wut not like the stocker has or i would have to do some weilding and cutting if i get a high flow?
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Mustang Man
Dodge Dakota
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4/13/2004
15:47:48
| RE: want to gut or remove cat? read this!
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If your truck is set up for unleaded fuel (hardened exhaust seats), then you won't burn any valves.
Running exhaust manifolds alone provides enough material to pull the excess heat away from the cylinder heads.
If you have any exhaust pipe connected to the manifolds, you're just that much safer. I wouldn't worry about burning a valve unless I had a set of heads that required leaded fuel(lead cools and lubricates the valves).
The exhaust system is part of tuning your engine. A huge, free-flowing exhaust will hurt low-end torque if you don't have a decent camshaft/heads/intake combo. Pick your parts and modifications to work in conjunction with one another, and you'll get gains in both torque and horsepower throughout the your desired r.p.m. range.
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Bob Lincoln
Dodge Dakota
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4/14/2004
12:55:02
|  RE: want to gut or remove cat? read this!
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None of you has addressed the issue that it's a felony to remove the cat, punishable by a $2,500 fine if you're a private citizen; $20,000 if you're a dealer or mechanic. But, hey, go for it and help reduce the federal deficit.
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uh
Dodge Dakota
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4/14/2004
18:30:41
| RE: want to gut or remove cat? read this!
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if indeed it is a felony, all of the gun lovers out there that do this and get caught WILL give up the right to own the guns they now own and the future right to purchase or be in the possesion of a firearm, meaning you can't even legally borrow one to hunt.
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J and J Auto
GenII
4/14/2004
20:44:33
| RE: want to gut or remove cat? read this!
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Typical 5 star mechanic don't know his A$$ from
a hole in the ground saying a gas motor needs
no back presure.
We should send that comment to detroit and see
what kind of mechaincs they hire to work on our
vehicles.
I usualy never blast anyone and this is a first
but I just had to
start the motor with no manifolds and it will not
even rev up
Mustang man hit it closer on the head
Hers another one to contemplate
Exhaust does not just flow it pulses and tuning the
exhaust for you particular setup will is the key
to good performance it does not just flow
pulse scaviging and more 5 star boy go back to
school they did not teach you that at chrysler
Larry
J&J Auto
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ccman
Dodge Dakota
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4/15/2004
23:53:33
| RE: want to gut or remove cat? read this!
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that is why i hate taking my truck to the dealer, they never fix anything, they say it is running fine. But i come to this site and everything you guys say to do works. I can't afford to pay the dealer big bucks when they think your smoking dope when you take a problem to them. I will ALWAYS come to this site!!
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ccman
Dodge Dakota
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4/15/2004
23:55:01
| RE: want to gut or remove cat? read this!
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Larry, you must really be pi$$ed off, you never bomb anyone. LOL
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