Removing Cats From Exhaust

[Old School]

And honestly, why wouldn't you run a cat?
I ain't no environmentalist, I dislike most of those folks. But running cats on a virtually stock car is a tiny loss in power.
And they clean up the exhaust by some 90% or something.

Heat. Cats basically double the exhaust temp. You can see this by taking temp readings, with an IR thermometer, just before and after the cat. Removing the cats results in reduced interior temps and vastly reduced sill temps.

[ViperTim]

Heat. Cats basically double the exhaust temp. You can see this by taking temp readings, with an IR thermometer, just before and after the cat. Removing the cats results in reduced interior temps and vastly reduced sill temps.

Yeah, Unfortinetly they cook the side sills...

So many cons and only 2 pros... (smell and environment)

[ellowviper]

Yeah, Unfortinetly they cook the side sills...

So many cons and only 2 pros... (smell and environment)

I hear ya. I just refinished my side sills...and I think I put the clear on too thick since after one good heat cycle, the clear split and spider-webbed something terrible. Oh well...too much clear isn't a good thing on side sills I've learned.

[Old School]

Yeah, Unfortinetly they cook the side sills...

So many cons and only 2 pros... (smell and environment)

For me it's down to 1 pro, I hate the smell of cats. You get that rotten egg smell anytime a Toyota (or whatever) goes WOT.

[ViperTim]

For me it's down to 1 pro, I hate the smell of cats. You get that rotten egg smell anytime a Toyota (or whatever) goes WOT.

I've never had that smell...

[plumcrazy]

if your car is boosted, ditch the cats immediately. if NA go with a high flow

[338LAI]

Hello,

Thanks for the advise! I went with high flow cats from Jon B. Removed muffler and drove car home after repairs on motor. It is loud! Maybe to loud. Used Team Hilton to do repairs and install HF cats. They loved the way the car sounds.

Ray

[ellowviper]

Hello,

Thanks for the advise! I went with high flow cats from Jon B. Removed muffler and drove car home after repairs on motor. It is loud! Maybe to loud. Used Team Hilton to do repairs and install HF cats. They loved the way the car sounds.

Ray

I don't think anyone said to remove the mufflers....

[dave6666]

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[Old School]

Hello,

Thanks for the advise! I went with high flow cats from Jon B. Removed muffler and drove car home after repairs on motor. It is loud! Maybe to loud. Used Team Hilton to do repairs and install HF cats. They loved the way the car sounds.

Ray

Too loud is in the ear of the beholder....

[GTS Dean]

Too loud is in the bleeding ear drums of the driver. They will come shortly.

[Bill W]

I think you should have left the mufflers on.

[Racngrn]

I went to Belanger Hi Flow cats and a Corsa cat back. It's loud, but a good loud. Can't imagine without mufflers. I'm not even sure I can get mine inspected at this sound level. We'll see.

[338LAI]

I think you should have left the mufflers on.

I took V in to a performance exhaust shop today to have mufflers installed.

Jon B helped me out and gave suggestions on muffler. I told the tech installing mufflers that I want a deep rich sound.

I should know tonight when I pick it up.

Ray

[ViperTim]

I went to Belanger Hi Flow cats and a Corsa cat back. It's loud, but a good loud. Can't imagine without mufflers. I'm not even sure I can get mine inspected at this sound level. We'll see.

Heard both straight pipes and corsa.
Straight pipes aren't that much louder than corsa imo.
But corsa is crisp and raspy. Straight pipes is.... Straight...

[dave6666]

If you really want that *peels paint* SPL put on side exhaust. The cars next to you will hate you and you will love it. The sound is incredible.

[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

[Bill Pemberton]

Key point is higher " low" end torque , which helps plenty getting it out of tight corners. If you are in Canada the rules may be different, but losing your cats will affect resale as well as your option on where to sell. Figure on most knowledgeable Dealers figuring 2K to repair and before you question this we had years where we saw over 300 Vipers go through the shop. The number of butchered exhaust systems was in the majority , and with cut up portions and more, it often entailed a new system with new oxygen sensors in addition. Bring this up because folks often find out the hard way and then state that it is easy to return back to stock when it seldom is.

[GTS Dean]

The key to getting out of "tight" corners depends on entry and exit speed. Bill, I know you have strong A-X roots, but moved to HSTT/RR later. A-X'ers are not shifting much, run pretty low speeds and use more of the rev range to get around. In my experience, any time you are under 3k rpm on a road course, you are gonna get your lunch eaten by people like me who are at or near the motor's torque peak all the time.

[Bill Pemberton]

Dean, understand tighter corners , exit and entry speed , quite well, as have been Road Racing/Instructing for 20+ years, and seldom got my lunch eaten by others in Vipers. The majority of folks will be driving on the street and many complained of lack of low end torque without cats and we ended up putting them back in for those who had removed them. Academic point and there are differing views and I accept that , but removing is a major cost concern in today's climate and I feel warning folks of the ( cost )consequences is the important information here. Resale/trade in will suffer in almost all States, imho.

[JonB ~ PartsRack]

As far as resale goes, OE cats WILL fail. And NOT be available.

One more reason to switch to bolt-on, no-cut, no weld HiFlow replacement cats. Keep your OE cats OE, before they quit at 50K miles or even before. If you dont replace plugs and wires every 20K miles, your cats will expire sooner.

[Dan Cragin]

Removing the catalyst is against the law and bad for the environment.

[dave6666]

Removing the catalyst is against the law and bad for the environment.

[SlowPoke McGee]

Removing the catalyst is against the law and bad for the environment.

Did Greta Thunberg hack into Dan’s account?

In all seriousness, I still remember when I was 18 years old and wanted to eek a few more hp out of a Firebird I owned at the time. Took it to a local mechanic and asked what he thought about removing the cats. He said the same thing.... bad for environment and govt might make it illegal. Well that was close to 25 years ago and while it’s still legal in my province 25 years later not to have cats, I guess the environmental argument remains unchanged. Only now it seems to becoming more amplified by the militant left to the point where some reasonable minded folks are pushing back just because they are tired of the PC crowd telling them which side to butter their bread. But I digress...

[Bill Pemberton]

Dan is in California and has a valid point for many States, but frankly the main concern I will continue to focus on is resale. Do a set of high flow cats ( Jon B. sells plenty of them) as regardless of all the other plusses and minuses folks will banter back and forth about , the resale issue is definitive.