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Catalytic converters

MY18VF2SV6TTAN1C

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Hi all.

Just had my 04 exec in to Holden for work and they told me the knocking I've been hearing is the cats. They said they could remove them or replace them, replacement being far more costly. They have removed them, but now there is a noticeable rattle when I put my foot down. Is it gonna do any damage without them? Is it better I get new ones put on? Forgive my ignorance but what do they actually do?

Cheers, ryan
 

Ozzie

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Not sure what state your in but every state ive lived in it is illegal to drive the car without them?
They are a DPI requirement and you can get a hefty fine when caught.
Not to mention your fuel economy might decrease and noise level highten
probebly best to have them on there. hows your exhaust attached now? or did they remove that too?
 

Skydrol

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The Converters does nothing for performance or operation of the vehicle. Their sole purpose in theory, is to change the exahust gases in to CO2 and Water Vapor. Just part of the Emission System. They are not perfect as we can see on emissions test. Depending on local smog regulations is required to be checked their funtionality or not. I am speaking from the USA experience, some states are tighter than others, some states do not even check for smog any more. I leave mine, at least the exhaust does not smells like an old car. If you can, get the old used one back. They have Platinum as a catalyst which is a precious metal. Recycle them, they fetch good money that can be applied for a set of High Flow Cats. In the USA recycling a Cat can bring some around $70 USD.

I can come with a more elaborate answer but let us keep it simple.
 

Benboy

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Not sure what state your in but every state ive lived in it is illegal to drive the car without them?
They are a DPI requirement and you can get a hefty fine when caught.
Not to mention your fuel economy might decrease and noise level highten
probebly best to have them on there. hows your exhaust attached now? or did they remove that too?

OP is in New Zealand I believe they don't have stringent environmental controls as in Australia so removal of Catalytic Converters probably not a legal issue.

What do Catalytic Converters do ? For the uninitiated - read on.........

A catalytic converter is an emissions control device that converts toxic gases and pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction). Catalytic converters are used with internal combustion engines fueled by either petrol (gasoline) or diesel—including lean-burn engines as well as kerosene heaters and stoves.

The first widespread introduction of catalytic converters was in the United States automobile market. To comply with the U.S. Environmental Protection Agency's stricter regulation of exhaust emissions, most gasoline-powered vehicles starting with the 1975 model year must be equipped with catalytic converters. These "two-way" converters combined oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). In 1991, two-way catalytic converters were rendered obsolete by "three-way" converters that also reduce oxides of nitrogen (NOx); however, two-way converters are still used for lean-burn engines.

Although catalytic converters are most commonly applied to exhaust systems in automobiles, they are also used on electrical generators, forklifts, mining equipment, trucks, buses, locomotives and motorcycles. They are also used on some wood stoves to control emissions. This is usually in response to government regulation, either through direct environmental regulation or through health and safety regulations.
 

Noeleter

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OP is in New Zealand I believe they don't have stringent environmental controls as in Australia so removal of Catalytic Converters probably not a legal issue.

What do Catalytic Converters do ? For the uninitiated - read on.........

A catalytic converter is an emissions control device that converts toxic gases and pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction). Catalytic converters are used with internal combustion engines fueled by either petrol (gasoline) or diesel—including lean-burn engines as well as kerosene heaters and stoves.

The first widespread introduction of catalytic converters was in the United States automobile market. To comply with the U.S. Environmental Protection Agency's stricter regulation of exhaust emissions, most gasoline-powered vehicles starting with the 1975 model year must be equipped with catalytic converters. These "two-way" converters combined oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). In 1991, two-way catalytic converters were rendered obsolete by "three-way" converters that also reduce oxides of nitrogen (NOx); however, two-way converters are still used for lean-burn engines.

Although catalytic converters are most commonly applied to exhaust systems in automobiles, they are also used on electrical generators, forklifts, mining equipment, trucks, buses, locomotives and motorcycles. They are also used on some wood stoves to control emissions. This is usually in response to government regulation, either through direct environmental regulation or through health and safety regulations.

Pretty broad statement saying NZ doesn't have stringent environmental controls. In many cases they are a lot more stringent than Australia and certainly a lot more sensible and based on science.
 

vr304

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Not a legal requirement to run cats here in NZ, I think 2010 model cars and up have to run them from memory but anything older is fine without as for doing damage to your car nope won't hurt ir
 

Skydrol

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Actually, not every country around the world plays the EPA games. In the USA while I was living in the state of Minnesota the Governor abolished all Smog stations. They found out the amount of polution was very low. Most in Central States does not have Smog checks; the ones they do, is about revenue. They found out by nit picking they can charge a fee and/or fine the motorist. The state of Colorado had even an Air Con check, if leaked freon was a fail and you were forced to fix or deain it. In California they are Nazis with the EPA and CARB. The Californians trying hard to change the environment, not becuase is bad is simply a desert and they want it all green. Los Angeles is in a bad natural spot where the air does not move, churns in the same place, is just dirty.

I am not advocating to remove all Cats, I think is a good idea but the excessive unreasonable regulations is way out of hand.
 

Not_An_Abba_Fan

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The rattle you are hearing is probably some of the broken cat in the muffler. The cats rattle because they break up, then the broken bits make their way into the rest of the system causing rattles further down. If you can't shake the bits out, you will have to replace the muffler as the broken bits of cat will move around and eventually block the exhaust flow.
 

Skydrol

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The rattle you are hearing is probably some of the broken cat in the muffler. The cats rattle because they break up, then the broken bits make their way into the rest of the system causing rattles further down. If you can't shake the bits out, you will have to replace the muffler as the broken bits of cat will move around and eventually block the exhaust flow.

It happened to me on a 01 Pontiac Grand Am. The root cause was a leaking lower intake manifold gasket. The engine ingested coolant by the lower intake manifold mating surfaces (bad gasket) and goes unnoticed. After a long time depending how much glycol was ingested, the Cat plugs up. Also, a running rich engine will make the Cat runs hotter; a meltdown will occur plugging the exhaust as mentioned before. Execess oil (bad rings, guide valves, overfill, etc...) will do that too. Most Cats does not fail on their own; something led them to failure.

Check your engine and see if is running in good working order.
 
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