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Topic Review (Newest First)
10-25-2011 08:24 AM
dalesy ......Not to mention that #1 You will probably never notice the miniscule increase in performance and #2 The federal fine for removing them(should you get caught in a smog check) is somewhere over $2000. Is it worth it?
10-25-2011 12:37 AM
sam_bo3 I can't say anything about the domestic cats. I have a Nissan 370Z that installing a high flow cat or ,like I did, test pipes nets you an extra 10-15hp to the wheels. It is about the same gains as installing a new cat back exhaust. Maybe Nissan just uses horrible flowing cars. My friend has knocked the cats out of 2 of his Titans and they both had noticable gains. I can't say what the actual figures were but we aren't emission tested in OK.

There are lots of diesels that run around here and lots have no cats. I know that the newer ones have problems if run with out cats but I don't know years. If it were mine I would find out when it got to be a nessesity. If yours is safe (I think it is) get some test pipes to replace your cats it you can. That way if you have a problem you can go back to them. My test pipes were $100 as aposed to 300+ for HFC's.
10-23-2011 12:33 PM
LATECH [QUOTE=WildBill]On vehicles with O2 sensors (all late model stuff) the cat actually does nothing for emissions UNLESS there is a fault with the computer, injectors, etc. The computer keeps the mixture so close to theoretically correct, the burn produces very little emissions. [QUOTE]

Actually this is not correct. Not to start a pissin match , but for clarification.
A Cat converter converts Carbon Monoxide ( CO) (very toxic) and unburnt hydrocarbon (HC) (Toxic and nasty) along with unspent Oxygen (O2) to Carbon Dioxide ( CO2) and water ( H2O ). A close stoitch will aid in the process as mentioned above.
CO2 and H2O along with unspent oxygen and other atmospheric gases are not toxic to plants animals and humans.
Carbon monoxide is deadly to breath, kills most anything and is a major component of acid rain. Something to remember when waxing your car.
Leave your cats alone.It turns poison into plant food.(CO2)
A fault with the electronics or the emmission system is usually what kills a cat.
10-23-2011 11:44 AM
WildBill
With O2 sensor...

On vehicles with O2 sensors (all late model stuff) the cat actually does nothing for emissions UNLESS there is a fault with the computer, injectors, etc. The computer keeps the mixture so close to theoretically correct, the burn produces very little emissions. On my particular choice of hot rodding fodor, (Jag's) removing the converter does not affect the emissions. In CT since the cars I work on are over 25 yrs old, there is only the sniffer and they pass that with or without the cats. That said, the new cats are so free flowing, I don't see any reason to remove them. If you have O2 sensors after the cat (cats) you run the risk of throwing code constantly. I'd leave the cats in place if you have the second set of sensors.
10-23-2011 11:20 AM
MARTINSR Ahhh,there you go, that makes sense. LOVE those carburetors!

Brian
10-23-2011 11:17 AM
Valkyrie5.7
Quote:
Originally Posted by MARTINSR
I don't know about your Chevy but I know that after a few experiences with AM converters we won't even put an AM one in let alone the thought of removing one altogether. If putting in an AM converter throws codes pulling one out should sure as heck do it.

But I am CLUELESS on these computer controlled cars. But the first time we replaced a cat with an AM and it had codes we couldn't clear, we then replaced it with an OEM and delivered the truck code free with not a hint of a problem we will stick to OEM converters.

Brian
Could you share what brand of AM cat was giving you problems? I don't want to start some brand-loyalty flame war, so PM if you want. Just curious for future reference.

- Cameron
10-23-2011 11:16 AM
Irelands child If it's a carbed vehicle with a normal electronic ignition, say HEI or DuraSpark, I wouldn't hesitate removing a cat. With all the electronics/computer, that cat is a part of the system and is really needed for proper operation.
10-23-2011 10:48 AM
MARTINSR I don't know about your Chevy but I know that after a few experiences with AM converters we won't even put an AM one in let alone the thought of removing one altogether. If putting in an AM converter throws codes pulling one out should sure as heck do it.

But I am CLUELESS on these computer controlled cars. But the first time we replaced a cat with an AM and it had codes we couldn't clear, we then replaced it with an OEM and delivered the truck code free with not a hint of a problem we will stick to OEM converters.

Brian
10-23-2011 09:59 AM
chucksrt If you remove the cats you will need to have the computer reflashed to ignore the rear o2's
10-23-2011 09:30 AM
boatbob2
Cats........

Hi,i removed the cat from my motor coach,cut it open,gutted it,welded it back togerther,and put it back on,picked up ABOUT 1/2 MPG,but,more power.(coach weigs 16,000 lbs.)
10-22-2011 03:17 PM
LATECH
Quote:
Originally Posted by BBLK4X4
I have a 2001 chevy 2500hd 8.1 liter does it hurt the engine to remove the catalytic converters ? I know legaly Im not suposed to remove them but would like to ler it breath more.
Leave them be. They flow well as Joe P said.
If you really want a little more ( I mean Little) performance,put on a dual exhaust from the cat back, and use an H or X pipe crossover. It will help a little, the sound will be worth it.
I see guys who gut their cats , and usually it is due to a mis diagnosis of the problem, then WE end up repairing the real problem, and they end up with the MIL lit up for days with a P0420 and P0430, that wont go away untill a new pair of cats is installed.
Unless they are plugged and you are so poor you cant pay attention, gutting a cat converter is UNHEALTHY , lots of time consuming work, and usually fails to deliver more than a nuisance with an MIL that wont go away.
The substrate inside is very BAD for your respritory system, leave the job for a proffesional.
10-22-2011 02:43 PM
123pugsy
Quote:
Originally Posted by BBLK4X4
I have a 2001 chevy 2500hd 8.1 liter does it hurt the engine to remove the catalytic converters ?
No it won't.
10-22-2011 02:09 PM
techinspector1
Quote:
Originally Posted by joe_padavano
Better look at your exhaust again, since parts house catalogs show BOTH upstream and downstream O2 sensors for your truck. In any case, why bother to remove them? Even it it doesn't throw a code, there will be no benefit unless the substrate has melted down in each cat.
The thing that would keep me from doing it is the prospect of a very large Federal fine for removing smog equipment. The other thing that would prevent it is that I know it's a bad idea to hot rod your daily driver. If you want to go fast, start a project with a car/truck that you don't have to drive every day. I've always liked swapping a V8 into a small sports car like an MGB. One evening at the drags, I teched an MGB street-driven roadster with a 460 Ford installed, so don't tell me it can't be done.
http://www.britishv8.org/Photos-MG-Conversions.htm
10-22-2011 02:02 PM
joe_padavano Better look at your exhaust again, since parts house catalogs show BOTH upstream and downstream O2 sensors for your truck. In any case, why bother to remove them? Even it it doesn't throw a code, there will be no benefit unless the substrate has melted down in each cat.
10-22-2011 12:04 PM
BBLK4X4
Cat removal

Mine only has the up stream sensors and they are up closer to the manifolds not down by the converters I just didnt know if it would hurt the engine to take them off
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