mufflers vs catalytic convertors

[mauve66]

has anyone just put cats on an older car instead of mufflers in order to try and pass an emissions state inspection??

i know a proper size cat, based on cubic inches, would be large and more expensive than mufflers
but from an emissions and noise standpoint............??

i had a 81 Z28 that i ripped the mufflers off going through a corn field (dont ask) and since i was living pay check to pay check in the military i just took out the rest of the rear pipes.  all i had left was a short Y pipe coming out of the cat that ended right under the front seats and the sound was about like having glass packs on, not excessive considering the mufflers were completely gone

[FLG]

They do emission on our cars in some states??

All we have here in NY is safety. I can run open headers if i wanted.

[resq302]

Back when Jersey had real inspections vs. the plug and play crap now to see how well your computer is running, they actually used to take a mirror on a stick and walk around and look at the underside of the car to make sure your mufflers and cat. converters were still there if they came on your car.  Pre-OBD days, they actually hooked up a sniffer hose to your car and could tell what your CO, CO2, NOX, etc levels were coming out of the tail pipe at idle.

[mauve66]

They do emission on our cars in some states??

All we have here in NY is safety. I can run open headers if i wanted.

i'm sure they would pull you over for noise violation though

[FLG]

Possibly at night they might bust balls... but we have been driving around in my friends mid 60s jeep sb car, open headers...get lots of  not pulled over yet 

[flyinlow]

Toyed with the idea. Cats up front and bullet mufflers in back. Thought I could kill two birds with one stone. No inspections in Ohio (yet). But standing behind the Charger when its running is brutal.

They make hi flow cats that are resonable now. You would need heat shields. Not sure how long they would last with aftermarket carbs and cams. Overheating would be a concern. I would hate to catch the car on fire.

But if I could keep the noise down and cleanup the exhuast without significant performance loss, I would consider it.

[mauve66]

heat shields?? they produce alot more heat than a regular muffler??

[adauto]

Back when Jersey had real inspections vs. the plug and play crap now to see how well your computer is running, they actually used to take a mirror on a stick and walk around and look at the underside of the car to make sure your mufflers and cat. converters were still there if they came on your car.  Pre-OBD days, they actually hooked up a sniffer hose to your car and could tell what your CO, CO2, NOX, etc levels were coming out of the tail pipe at idle.

Wisconsin the same way...  

[mauve66]

Back when Jersey had real inspections vs. the plug and play crap now to see how well your computer is running, they actually used to take a mirror on a stick and walk around and look at the underside of the car to make sure your mufflers and cat. converters were still there if they came on your car.  Pre-OBD days, they actually hooked up a sniffer hose to your car and could tell what your CO, CO2, NOX, etc levels were coming out of the tail pipe at idle.

but older cars that are still under the emissions testing will still have to have the sniffer test since they dont have the plug in

[resq302]

Back when Jersey had real inspections vs. the plug and play crap now to see how well your computer is running, they actually used to take a mirror on a stick and walk around and look at the underside of the car to make sure your mufflers and cat. converters were still there if they came on your car.  Pre-OBD days, they actually hooked up a sniffer hose to your car and could tell what your CO, CO2, NOX, etc levels were coming out of the tail pipe at idle.

but older cars that are still under the emissions testing will still have to have the sniffer test since they dont have the plug in

Yes, but now they put it on a dyno and get it up to a certain speed at the wheels and then take a sniffer test reading.  Back in the day, they used to do an idle test which I thought was stupid since 90% of the time, the cars are driving and not idling.

[Cooter]

Be carefull Installing cats on Carb'ed/ Cammed engines as the converters aren't designed, nor will they last very long on a car that is running VERY rich....The Catalyst will not hold up long when subjected to rich conditions, Hense why the newer cars Check engine light will "Flash" at you if there's a potenially damaging misfire going on with the F.I.  Contrary to popular belief, cat .converters will NOT clean up your engines rich exhaust....You are waiting your money. They will smell like rotten eggs in no time (Sulpher)...

[resq302]

Be carefull Installing cats on Carb'ed/ Cammed engines as the converters aren't designed, nor will they last very long on a car that is running VERY rich....The Catalyst will not hold up long when subjected to rich conditions, Hense why the newer cars Check engine light will "Flash" at you if there's a potenially damaging misfire going on with the F.I.  Contrary to popular belief, cat .converters will NOT clean up your engines rich exhaust....You are waiting your money. They will smell like rotten eggs in no time (Sulpher)...

Which is why people disconnected the exhaust and rammed out the honeycomb inside the cat's back in the day.  Then reconnected the exhaust and fool the guys at inspection since you "have" your cat, you are in compliance.   Now if you do that today, your computer will throw a code.

[Cooter]

Be carefull Installing cats on Carb'ed/ Cammed engines as the converters aren't designed, nor will they last very long on a car that is running VERY rich....The Catalyst will not hold up long when subjected to rich conditions, Hense why the newer cars Check engine light will "Flash" at you if there's a potenially damaging misfire going on with the F.I.  Contrary to popular belief, cat .converters will NOT clean up your engines rich exhaust....You are waiting your money. They will smell like rotten eggs in no time (Sulpher)...

Which is why people disconnected the exhaust and rammed out the honeycomb inside the cat's back in the day.  Then reconnected the exhaust and fool the guys at inspection since you "have" your cat, you are in compliance.   Now if you do that today, your computer will throw a code.

They have gotten it down to a science today..You cannot f*ck with ANYTHING on the newer cars today without causing more harm than you did good....I find it so funny when the guys post things like this "Hey guys, I just put on this "Hot Air" intake (As it pulls the hottest underhood air right off the rad. fans when those stupid ass cone filters are run on the end of a pipe next to the rad. instead of up front, ahead of the rad. support to actually GET COLD AIR), and now my Check Engine light is on..Any ideas?"

Another good one "Hey guys, I just ran some Cam 2 LEADED racing fuel through the 'ole Charger with cats, now my Check Engine light is on..Any ideas?"

When if they actually understood the newer cars, running that fuel does NOTHING for performance and the lead in the racing fuel just stopped up their cat. converters....Also, you try and bump the timing even IF the car even has a distributor, and the computer takes back control and puts it right back where it likes it...So funny...

[resq302]

Yup, gone are the days of hmmm..... I have no fuel.  Lets see.... either its my carb, fuel pump, or I ran out of gas.  Today its like, hmmm.... I have no fuel.  Is it the fuel pump, the fuel pump relay, the injectors, the computer, the relay for the compter, the sensor for the injectors, etc.  Oh wait, I need a damn computer to figure out mechanics on a car. 

I think my next truck will be an antique that I will totally rebuild.  No computer, no fuss, no mess.

[matrout76]

I have only a single cat on my Jeep Scrambler and it sounds pretty good!

Its an 1984 CJ-8 with an AMC 360.  I'm running the factory exhaust manifolds into a single 2.5" pipe.  just after the Y, i have a high-flow 2.5" in and out catalytic converter.  the single 2.5" goes the rest of the way out the rear.  i run this jeep on the street, and on the sand dunes up in Michigan.  i wanted a good balance of torque and horsepower, so thats why i kept the manifolds and ran a large single pipe.

I had the exhaust done by a local shop and to be compliant with the law, they had to install a converter.  originally my plan was to cut it out when i got home and put in a flowmaster.  but, after owning a few jeep CJ's prior to this, i noticed something that i really liked...

because of the aerodynamic properties of the CJ (none), the smell of exhaust was alway noticeable while driving.  also, i always noticed that my clothes smelled like exhaust.  With the cat on, i didn't have any exhaust smell.

Since then, quite a few guys in my local 'wheeling club have done the same thing and everyone has been happy with it.  as soon as i redo the exhaust on my 91 Wrangler that i rock-crawl and trail run, its going to get a cat-only exhaust.

on the 360, the sound is pretty tame until you really open it up.  the 4.0L I-6 in the wrangler will always sound like a tractor engine, so i don't really care how it ends up.

[flyinlow]

most converters have a heat shield between the body of the cat and the car body if they are close to each other.

Why would you run an engine very rich except for cold starts?  I have a wide ratio a/f guage. spends most of its time 14-15 to 1 range under light acceleration and cruise . 13 to 1 at idle (smoothest) and 12 to one under WOT.  In would think a cat could handle this.

The overlap of my  Vodoo cam might be a problem. Unburnt hydrocabons at low rpm's go up fast with any increase in valve overlap ,similar to the problems a 2 stoke engine has meeting emission standards. All that excess gas would have to be oxyidized by the cat.  We did run converters on the carbed cars from 1975 until about 1985. The did not make much power and frequently ran poorly.

[Cooter]

  We did run converters on the carbed cars from 1975 until about 1985. The did not make much power and frequently ran poorly.

Yep, and if you've ever driven, worked on, or even owned one, you would know EXACTLY what I'm referring to when I say "Rich" when dealing with carb's...That A/F ratio gauge mnight SAY 14:1 andso did the engineers when they made the T-Quad to where you couldn't mess with the idle mixture screws cause it was "Factory" set at 14:1, but they still ran like sh*t and clogged the converters....A carb cannot, will not, and basically isn't designed to run as Fuel inj. does.

[mauve66]

Yes, but now they put it on a dyno and get it up to a certain speed at the wheels and then take a sniffer test reading.  Back in the day, they used to do an idle test which I thought was stupid since 90% of the time, the cars are driving and not idling.

out here  they don't have the rollers for older cars

Be carefull Installing cats on Carb'ed/ Cammed engines as the converters aren't designed, nor will they last very long on a car that is running VERY rich....The Catalyst will not hold up long when subjected to rich conditions, Hense why the newer cars Check engine light will "Flash" at you if there's a potenially damaging misfire going on with the F.I.  Contrary to popular belief, cat .converters will NOT clean up your engines rich exhaust....You are waiting your money. They will smell like rotten eggs in no time (Sulpher)...

ok, thanks

[Dmichels]

I had a mildly built 440 in my 68 All I had for emissions was a PVC valve. It was tunned up perfect and I would pass the NJ sniffer test no problem I don't remember the numbers but they were well within the limits. Now the car is registered as a classic meaning NO inspection I think many other states have similar programs
Dave

[TylerCharger69]

Due to the age of my car....all that is required is to have a hose from my pcv breather to the air cleaner....That's here in Texas though......Aren't older cars that were built before the emissions laws grandfathered?

[mauve66]

to a point but they still have to pass a sniffer in several places
when i was in CO it was for 69 and newer cars but that was 20 yrs ago so maybe its later years now,
reason i'm asking is 2 fold,
1. with a much larger  (512-540) producing more power i wouldn't think it would pass a sniffer for a stock 383
2. if i put a v8 in my ranger would it take four cats to subdue the larger engine to pass at a 4 cyl ranger  level??

i asked a local test shop and they said they can't advise me on swaping motors

[six-tee-nine]

Be carefull Installing cats on Carb'ed/ Cammed engines as the converters aren't designed, nor will they last very long on a car that is running VERY rich....The Catalyst will not hold up long when subjected to rich conditions, Hense why the newer cars Check engine light will "Flash" at you if there's a potenially damaging misfire going on with the F.I.  Contrary to popular belief, cat .converters will NOT clean up your engines rich exhaust....You are waiting your money. They will smell like rotten eggs in no time (Sulpher)...

Which is why people disconnected the exhaust and rammed out the honeycomb inside the cat's back in the day.  Then reconnected the exhaust and fool the guys at inspection since you "have" your cat, you are in compliance.   Now if you do that today, your computer will throw a code.

There has'nt changed much in all these years.......
All the modern diesel (of wich there are ALOT on the European roads)engines have a nox cat in their exhaust line. But after a while they get blocked from carbon built up inside. New ones cost alot so you don't want to know how much of them i've cut open to get the guts out and weld them shut again...