Removing Cats From Exhaust

[338LAI]

Hello,

I would like to introduce myself as a new member here and have a couple questions.

I would like to remove the cats off one of my 1998 Vipers.

I have been told they are clogged and have a rotten egg smell to them.

Can this be done properly with out removing the sensors if they are reprogrammed?

Was also considering installing a new set of Belanger headers and cat back exhaust. However, I do not know if they can be installed without removing the motor. What is my best option? FYI: I do not need emissions.

Would like to know the best option available to me.

Thanks in advance!

Ray

[dave6666]

Rotten egg smell = bad primary O2 sensors. Put new factory NTK in not cheapo Bosch.

No exhaust work requires altering the location of the motor.

Belanger headers will likely result in preheat CELs. The fast heat sensors are junk. The code can be tuned out by a competent tuner.

You may get rear sensor codes with no cats. I use a single oil fouler per side to eliminate that.

[Lalmeida617]

Rotten egg smell = bad primary O2 sensors. Put new factory NTK in not cheapo Bosch.

No exhaust work requires altering the location of the motor.

Belanger headers will likely result in preheat CELs. The fast heat sensors are junk. The code can be tuned out by a competent tuner.

You may get rear sensor codes with no cats. I use a single oil fouler per side to eliminate that.

Dave if one were to replace the cats with a high flow set, would there be any CEL issues or oil foulers needed?

[dave6666]

Should not be but Belanger headers are famous for the preheat code which is not really related to cats or not. I ran H/F cats for over 10 years and never had a cat related code. Just the preheat code. Dan Lesser tuned it out.

[JonB ~ PartsRack]

Compromise and go with HF cats vs catless. No stink, no backfire, no codes....

As D6666666 sez, no motor removal !!!

Labor Day Sale on cats and ALL Belanger products at PartsRack.

JonB@PartsRack.com

Thanks

https://driveviper.com/forums/thread...long-ago/page3

[Old School]

I have a Gen3 with no cats and no CEL. The downstream O2's are installed with spacers.

[ticklechicken]

I installed these and they work great. No smell. Cheap, buy you have to add some straight pipe yourself.

Here's a comparison between the high flow and stock. You can see how clogged mine got in only 20k miles.

vp_20190319_150234.jpg

vp_20190319_150526.jpg vp_20190319_150559.jpg

[Fatboy 18]

Or just chuck a bit of pipe in there

[JonB ~ PartsRack]

Cats are like a toilet. If you put clogging stuff in, they get clogged. Dont blame the toilet..blame the waste.

Rich-Running, unburned fuel, can clog a cat in 1000 miles or less! Routine Things happen to foul cats:

Bad Spark Plug? Bad Wire? Bad Coil? OLD plugs? OLD wires?

If the fuel does not burn completely (or at all) it carbons-up the GOOD cat.

The V-1o has such massive TQ that it is difficult to detect a miss...... Mis-Fire = Fouling

[338LAI]

Cats are like a toilet. If you put clogging stuff in, they get clogged. Dont blame the toilet..blame the waste.

Rich-Running, unburned fuel, can clog a cat in 1000 miles or less! Routine Things happen to foul cats:

Bad Spark Plug? Bad Wire? Bad Coil? OLD plugs? OLD wires?

If the fuel does not burn completely (or at all) it carbons-up the GOOD cat.

The V-1o has such massive TQ that it is difficult to detect a miss...... Mis-Fire = Fouling

Hello everyone,
Lots of good info here! A little history here, I have only had this 98 for a couple months or so. The car has a miss and sounds like a lifter or two knocking. I know at least one cylinder is not firing. I replaced the plugs with OEM plugs...no change. Engine oil has gas smell as well. Car runs okay but has low idle miss and RPM at idle is about 500 rpm.

My mechanic is Adam Hilton from Team Hilton doing the work on car. I bout new coil pac's and have a new set of OEM wires. Have not installed any of these yet but something is wrong and what Jon B stated hit the nail on the head.

I have the hood and exhaust covers off the car and figured I need to resolve clogged cat issue at the same time engine is being worked on. Not sure what HF cats are but (High Flow) assume Jon B sells them.

FYI: mechanic thinks that lifter knock will go away once we find the issue?? Also he is strongly suggesting I use Rotella 15-40 motor oil for its cleaning properties...thoughts?

Thanks,
Ray

[Bill Pemberton]

Please consider what Jon B is suggesting , and I wish to add another issue. Owners who have decided to go with no cats can run into issues with lower resale as this is one notation on many Dealer Purchase agreements ( consumer statement that the exhaust is intact or items have not been removed ). This is not just in States requiring Emissions testing , it is also listed in many States as removal of a catalytic converter must be listed at an Auction. There is a common sense understanding that converters go bad and at some point need replacing , so the use of a high flow cat has been viewed as a possible replacement. So you not only will have a stinky car , you jeopardize your resale as most Dealers will assess a rather sizable sum to correct exhaust issues.

The other thing , often not commented on , is the motor does benefit from the back pressure with the low end torque , and frankly the secret about the Viper's success over the years has really been about the massive torque and not necessarily the horsepower. It helped the 90s models confuse the skeptics who said a big block, and all the weight up front would not be a solid racecar -- surprise with the major with FIA and the overall win at Daytona in 2000.

[SlowPoke McGee]

Please consider what Jon B is suggesting , and I wish to add another issue. Owners who have decided to go with no cats can run into issues with lower resale as this is one notation on many Dealer Purchase agreements ( consumer statement that the exhaust is intact or items have not been removed ). This is not just in States requiring Emissions testing , it is also listed in many States as removal of a catalytic converter must be listed at an Auction. There is a common sense understanding that converters go bad and at some point need replacing , so the use of a high flow cat has been viewed as a possible replacement. So you not only will have a stinky car , you jeopardize your resale as most Dealers will assess a rather sizable sum to correct exhaust issues.

The other thing , often not commented on , is the motor does benefit from the back pressure with the low end torque , and frankly the secret about the Viper's success over the years has really been about the massive torque and not necessarily the horsepower. It helped the 90s models confuse the skeptics who said a big block, and all the weight up front would not be a solid racecar -- surprise with the major with FIA and the overall win at Daytona in 2000.

I think this may be an urban myth. Quite sure most dyno’s would correlate higher exhaust flow with higher overall torque curve.

https://youtu.be/_PVXvHkr-Vs

[338LAI]

I believe this is what Jon B suggested for HF Cats.

http://www.viperpartsrack.com/viper-...converters-srt

Thanks in advance for your help!

Ray

[GTS Dean]

Diesel oils have a MUCH more robust additive package than gasoline oils and will easily offer longer drain intervals than standard. If you know your motor has been misfiring and loading up the crank case with fuel and combustion byproducts, then I would definitely recommend Rotella for at least the first fill.

[338LAI]

Diesel oils have a MUCH more robust additive package than gasoline oils and will easily offer longer drain intervals than standard. If you know your motor has been misfiring and loading up the crank case with fuel and combustion byproducts, then I would definitely recommend Rotella for at least the first fill.

Thank you and yes it is definitely loading up and misfiring. Will give it a try

Ray

[rstihl69]

Are the cheap bosch o2 sensors really that shit?

[dave6666]

Are the cheap bosch o2 sensors really that shit?

Most people drill holes in them. That ruins them and your car won't run perfectly.

[ellowviper]

https://www.thunderboltperformance.com/
I've ran these spun SS 3" in/out cats off and on for years. Work really well, off market brand, who knows... might be rebranded by some of the more well known/expensive labels. One never knows..... I have two brand new ones in the box on the shelf that aren't going to be used anytime soon. I offer them up if you want to give them a try. Just pay $25.00 for shipping. Let me know.

[Trick]

I went cat-less with the Snakeoyl axle back, and it sounded like shit, added moroso spirals and that sounds great.

[ellowviper]

I went cat-less with the Snakeoyl axle back, and it sounded like shit, added moroso spirals and that sounds great.

This. I have dual moroso spirals on each side....sounds amazing.

[Trick]

I only did spirals in place of the cats left the stock resonator... I'm @ 3500 feet and have great pops and whistles coming from the back end

[ViperTim]

I wonder how people kill their cats.
I have some off brand cats already installed in my car.
And I beat the shit out of my car everytime I drive it.
Haven't had it failing yet!

But, big question. Will the car spit flames as catless?

[Old School]

But, big question. Will the car spit flames as catless?

Goals

[ViperTim]

Goals

Gotta have them priorities

[JonB ~ PartsRack]

I wonder how people kill their cats. SEE ANSWER IN POST ABOVE ABOUT MISFIRES
I have some off brand cats already installed in my car.
And I beat the shit out of my car everytime I drive it.
Haven't had it failing yet! NO MISFIRES !!!

But, big question. Will the car spit flames as catless? YEAR MATTERS....PCM MATTERS.... SIDEPIPES PROBABLY; REAR OUTLET PROB NOT; GOOD THING TOO, SINCE REAR BUMPER PLASTIC MELTS AND BURNS!!

Answers within quotes