I almost forgot to mention another huge advantage if you remove a cat. converter or remove all of them. ONE LESS THING TO WORRY ABOUT, with the 8 billion things you have to worry about breaking and then replacing cat. converters are not cheap to replace and if one gos bad it can cause problems for example on my ranger if the first cat. blew out that is nearest the engine it would clog the second which means the exhaust has a huge plug it in and well lets just say your going to have to gimp home very slowly or have it towed. When i get my truck i dont want to worry about some stupid cat. blowing out and causing problems. Now to you folks that offroad if you have 2 cats. be very careful on what you go over... If you come down hard on a rock it can and most likely will cause your cat. to break apart and if its that first one its going to clog that second one and end your fun. The newer the cat. the less likely it will break apart but after time they become more fragile. On my old 95 f150 with the 351w i ran true dual straight pipes and what i mean by straight pipes is no mufflers or cats. just piping from the manifolds back with a H pipe. Yes it was loud, but it ran a ton better especially after 2500 rpms it was like a whole new beast. Now the small exhaust piping, and big muffler restricted it but the big ole cat. probably did as well. If you actually see the honeycomb in a cat. its not very free flowing at all. Take your air filter out, put your hand on one side and blow through it. Yes they are diffrent but the same idea, you cannot feel very much air at all. Thats what a cat. dos to the exhaust it has to filter out all the emissions so to speak so it has to be very thick. If you dont know what the honeycomb looks like go to google images and take a look and you will see why people say its restrictive. Now when i get the $ i will be pulling off one of the cats. and replacing the muffler with something more free flowing. I had a 98 z28 camaro with MAF and it did not have any problems with running without cats. and it had 2 total maybe even 3? Also had a 95 Z28 without any cats that ran perfectly fine. I know there was one on each side of the Y pipe but they were all removed needless to say. The check engine light was on for a day or so and would pop on randomly for a few seconds or so and go back off every once in awhile. It was not tuned what so ever either, now i do not know much about MAF but have been told its very "adaptive" meaning it will adjust to a certain extent. So besides maybe having a check engine light on i dont see why if you removed both it would have any problems. It may run rich for alittle while till the computer "adapts" but other then that i dont see a problem. The only reason i will probably leave one cat. on my ranger is i do not want it very loud. But the second one will be gone for sure along with that factory muffler and replaced with a cherry bomb muffler or magnaflow.

 

Thats nice an all, but the cat if properly designed is not something to worry about. The cat only plugs and fails when the engine is allowed to run out of tune. Misfires, fualty O2 sensors, lean conditions, etc. These are among the things that cause cat failure. The converter has no moving parts and does not wear out or degrade unless something causes it.

Fords in particular have excellent cat designs. This doesn't apply to all models, but most of the trucks have appropriately sized and designed units. This is especially true of the Ranger and the older explorers (pre 2003). So rattling or plugging without a definite cause is unlikely.

Also comparing the cat to a filter is an incorrect and inappropriate comparison. The substrate is arranged in a honeycomb type design with cells that go straight through. Nothing gets trapped as a filter would do, everything flows through. The secrete is the precious metal coating used on the substrate. The ingredients needed to convert the harmful gases into harmless gases is already found within the gases themselves. However, normally they need a lot of heat and pressure to finish burning completely. The platinum group metals make so this burning can take place without the pressure and at a fraction of the heat. The reaction takes place on contact. Nothing is being filtered. Most cats are appropriately sized for this, so the amount of restriction to flow they pose is minimal, and would only have an effect at higher RPM. This was not entirely true of older converter designs. In the early days the converters were often undersized, and the ceramic substrate was thinker, leaving less room for the exhaust gases. Also earlier designs did not have as precise of fuel management, which allowed the vehicles to run rich enough that they could plug their own converters. The pellet type converters are no longer in use, but they were very restrictive.

However there is still always the danger that the cat could break or plug due to a physical impact. How likely this is depends on what you do, but on road driving still has its dangers. Any debris on the highways can if you get unlucky enough, hit a converter hard enough to shatter it internally. My converter on my van failed due to a physical impact of unknown origin. The dent could be seen clearly, but it is unknown when this occurred.

 

Lets get rid of the DPF's on diesel vehicles too.. waste of fuel