Removing Stock Cats

[MAMBA]

I have stock headers and stock cats followed by Belanger Cat Back muffler on my 95 RT/10. I am considering removing the stock cats and replacing with a 3" tube. I know it will be louder but also keep the temp of the side exhaust cooler. It seems to me I read on previous posts somewhere that removing the cats may cause a strong gas smell from the exhaust to be very prominent. Is that correct? I sure don't want to be smelling obnoxious fumes. I would really like to get rid of the cats altogether but if the fumes really are a problem, I guess I'll go with high flow cats.

 

[FE 065]

I think I noticed more bad odors when I put mine back on. Don't sweat it

 

[SNKEBIT]

mine doesn't smell. 3" from the manifolds to exit.
I think the OBDII cars are more subect to a gas smell than the Gen.1's are, it might have something to do with the second O2 sensor????

 

[Doc.]

MAMBA,

My '96 GTS smelled so bad without the cats that I could not drive it. All problems were solved with high flow cats.

Doc.

 

[mopar75110]

I took the cats off my 94 and replaced them with a 3" tube into a Borla muffler. It immediately ran cooler--both the engine and the side sills. It performed much better also, (nearly 4 tenths better at Houston Raceway Park). I like the increased noise, but some find it too loud. If you have never looked into a cat that has been removed you would be amazed at how restrictive it looks.

 

[Jerry Dobson]

If you remove your cats, don't advertise it. The Viper hides it real nice behind the side sills.

The EPA fines are up to $2500 for you and $25,000 for the shop that removed them.

In August 1986, the U.S. Environmental Protection Agency (EPA) issued new proposed guidelines for the construction, efficiency, and installation of aftermarket converters. The EPA guidelines state that replacement converters may be installed only in the following situations:

The vehicle is missing a converter.

The state or local inspection program has determined that the existing converter needs replacement.

The vehicle has exceeded the age or mileage conditions of the original equipment catalytic converter. Consult vehicle owner’s manual or emissions warranty manual for specific details on your vehicle.

Additionally, a legitimate need for replacement has been established and documented.
The installer must include the customer’s name, address, and the make, model, year, and mileage of the vehicle on the service invoice, along with a stated reason for replacement. Where a state or local government has determined that a converter is damaged or needs replacement, the service or repair facility must retain a copy of the written statement or order by a proper government representative which indicated that the converter should be replaced and attach it to the invoice. Where the replacement need has not been verified by a proper state or local government representative, the customer and a representative of the service or repair facility must sign a statement verifying that replacement is justified.
Furthermore, the EPA has issued the following installation requirements:

The converter be installed in one of the three situations outlined above.
The converter be installed in the same location as the original converter.
The converter be the same type as the original converter (i.e. oxidation, three-way, or three-way plus oxidation).
The converter be the proper one for the vehicle application as determined and specified by the manufacturer.
The converter be connected properly to any existing air injection components on the vehicle.
The converter be installed with any other required converters for a particular application.
The converter be accompanied by a warranty information card to be filled out by the installer.
Federal law prohibits removal or replacement of properly functioning O.E. catalytic converters.

 

[GTS Bruce]

No cats on my 01.Occasional strong exhaust smell.When you percieve the smell which is no worse than a 60's vintage car its the same as that stupid 1-2 shift arrow light.It means get going! GTS Bruce

 

[Early93Viper]

Won't you get a check engine light if you remove cats????????

 

[Ulysses]

On a 95 you won't. No rear O2's.

 

[MAMBA]

Once again guys, thanks for the feedback. I think I'll give it a try and see. Worse case I put a set of high flow cats on.

 

[FrankBarba]

95's had stock headers? mine did not have stock headers. Was your 95 special ordered with Headers?

 

[rcdice]

RE: the EPA warnings,

When I received my Random Tech 3" cats I noticed that language on a flyer in the box. I was concerned whether the installer would give me any grief or not.

Nope. None. I wanted a Viper Tech to do the install (and a few other maintenance items at the same time. Work order from the Dodge dealership said "customer requests after market exhaust and free flow convertor install". They did the work, welded the cats in place just right. No problems, nothing ever questioned.

 

[Phil Lee 94 red RT]

You won't smell anything when your moving, but the cars behind you will. I was behind a gen I with no cats in a parade once. Thought I was going to choke from the fumes. Put high flow cats on. You'll run much cooler and have more horses and you won't stink!!!!!!

 

[MadMaxx]

2.5" inlet dynomax "bullit" mufflers from summit fit right in place of stock cats. Sawszall the cat off just outside the factory weld points, loosen the rear exhaust hanger and slip the new muffler in. It will quiet you down a tad, but louder than with a cat for sure.

 

[2002_Viper_GTS_ACR]

do the high flow cats.. TRUST ME.. it stinks if you just remove the stock ones

Its not too bad for you, AS LONG as your moving, and as long as you have the windows set right (meaning, at a certain opening point, it creates some wierd vacuum and the spell comes into the car. That aside, assuming you leave your windows open enough, or closed enough, and are moving, you STILL have the problem that anyone behind you is going to hate you. I did this, and eveyone of my friends ******* about the smell. The MINIMAL power gains over high flow cats, that might arrise from NO cats, just ISNT WORTH IT.

But go ahead, go through all the trouble, to come to the same conclusion, that so many of us here already have.

Jon

 

[MadMaxx]

I never had any problems running strait exhaust. Perhaps that's because I've been around drag strips and muscle cars so long I'm imune hehe.

 

[Brian 95 RT]

Has anyone with a stock exhaust manifold removed the stock cats and mufflers, and replaced them with just a 30" Dynomax Bullit or Ultraflow mufflers, or the 30" Summit Chambered mufflers? I would think these longer mufflers would tone it down enough to make the noise level bearable???

I still haven't changed the exhaust system on my '95 yet. Was going to go with the Roe high flow cats & mufflers, but have gotten too many mixed reviews on them. I'll keep searching!

 

[Shelby3]

I'm running no cats and am getting no adverse smell. The car is actually quieter than when I had the random tech metal high flow cats on. Especially during deceleration.

 

[Early93Viper]

What kind of HP gain can you get with no cats......say on a 93 RT/10?

 

[95Viper]

Brian, I took a stock 95 setup and just replaced cats with straight pipe, kept everything else the same. I couldn't be happier. I'm about an hour from you, maybe next summer we can take a drive before you do anything.

 

[MAMBA]

Craig,
Thanks for the input. I'm going to replace my stock cats with the straight 3" pipe this week. If for some reason I'm not happy with it I can always go with the high flow cats.

 

[Brian 95 RT]

Thanks, Craig. I'll probably take you up on your offer next summer.

Brian

 

[95Viper]

Mamba, I'm not sure what the rest of your exhaust setup is but the stock cats aren't 3". Neither are the stock flex pipes. You don't want to go up and down in sizes so keep everything one diameter. You'll lose HP otherwise.

If you re going with 3", do it from new headers, new flexpipe, highflow or no cats, through mufflers and out. All 3".

P.S. I've read a lot about engines needing a certain amount of backpressure for optimum HP. I haven't seen dyno pulls with configuration changes but you might hurt your power if you go with little to no back pressure. Just something else to think about.

 

[FE 065]

Engines needing backpressure for max hp is mostly a myth. The key is, if the engine can be tuned for (or if the computer compensates for..) any changes in backpressure, power will not suffer.

I don't think I've seen an engine dyno test where they increased backpressure to gain hp...

They might go to smaller header primaries, but that's to keep exhaust gas velocity high and induce better cylinder filling, not to increase backpressure.

 

[MAMBA]

I've got stock headers and flex pipe. The end of the flex pipe entering the stock cat is 2-1/2" and the stock cat exits into a 3" opening for the Belanger cat back muffler. So if I delete the stock cat I need a pipe to go from 2-1/2" to 3". Am I missing something.

 

[95Viper]

FE065, I always assumed you are right but I have read otherwise. I'd love to see dyno pulls with different exhaust configs all run on the same day.

Mamba, The rule would have been not to go up to a 3" catback if the rest of the system is at 2 1/2". I've never seen dyno pulls on this either so maybe it's a myth like the above. The reverse funnel theory supposedly disturbs the airflow as you step up to 3" in the pipe. If I were you, I'd place the step up pipe as close to the muffler inlet as possible.

Sure wish I had a dyno. I'd get 9 or 10 different exhaust setups and try all these theories out.

 

[Achilles99]

I've got stock headers and flex pipe. The end of the flex pipe entering the stock cat is 2-1/2" and the stock cat exits into a 3" opening for the Belanger cat back muffler. So if I delete the stock cat I need a pipe to go from 2-1/2" to 3". Am I missing something.

Are you sure your stock cats exit into a 3" opening? I just removed my stock cats... I know for sure that it was 2.5" on both sides. Most likely, your cat back muffler is 3", but reduces to 2.5" so that it can bolt right up to the stock cats. That's the way Borlas and Corsas are (I've had both). On my last Viper, I replaced the cats with a 3" section (and cut the 2.5" reducer off the catback, while using a 3" to 2.5" reducer to mate up to the flex pipe end left after cutting out the cats). This time, I used a 2.5" straightpipe. Using an exhaust flare (Autozone rents them out for free, just get the larger one), I slipped the straight pipe over the flex pipe end (cat cut off), and on the other side of the straight pipe I put the end of it into the 2.5" receiver of my catback. No band clamps required, just regular muffler clamps. No leaks so far, knock on wood. I did put exhaust tape around the seams, just to be sure. I used the kind that you dip into water and add a catalyst to make it hard... kinda like setting a cast for a broken bone.

 

[MAMBA]

Whoever installed the catback cut the exit of the stock cat at the 3" diameter on the taper and then welded it to the 3" inlet of the catback muffler. I'd post a picture but so far I haven't been able to. Do you have to have your own website to download a picture here?

 

[Achilles99]

MAMBA,

Click on Media, and go to user Gallery. You can create your own, and add as many pictures as you like. The cool part is if you click on the picture while in your Gallery, you get a link you can copy (called the UBB Code). By pasting that link in a regular post that you make, the picture will show up inside your post. Cool, eh? I've shown your pic below:

 

[MAMBA]

Well I finally replaced the stock cats with the 3" straight pipes to see if I going to stay with them or go with the high flow cats. It certainly is louder but in my opinion not obnoxious. I just have to straighten all the pictures in the house after I've started it in the garage! What I do have is an annoying buzz or vibration which seems to be coming from the passenger side exhaust. I've checked all the joints and everything is very solid although I do have just a little bit of a leak on the front joint of passenger side which I will seal up, but would that small leak make a resonance buzz or vibration? It only does it at idle. When I blip the throttle it stops. I also have a little popping on decel which could be attributed to the exhaust leaks. I used muffler clamps at the joints but I may weld the joints if that is the problem. There is a picture in my gallery showing the 3" pipes added. I have not noticed any real strong fumes yet but I will drive it a while and see if the noise level or the fumes become a problem. If so, I will still go with the high flo cats.