Keep cats or not, please help
#1
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I cut off my cats becsuse i bieved they were clogged because it was running funny, turned out that the driver side cat was fine, and passenger side was hollowed out
My question is, if i reinstall cats, will the truck run better than before, and second
Can i just get 2 regulat 2.5 inch cats and have them welded on. Or do i need the whole assembly
My question is, if i reinstall cats, will the truck run better than before, and second
Can i just get 2 regulat 2.5 inch cats and have them welded on. Or do i need the whole assembly
#2
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Cats don't make any engine run "better", they are simply an emissions control device. The engine will always make more power and attain better fuel economy if the exhaust system is optimized for the application sans cats.
However, there are certainly some high flow cat options that won't do much at all to negatively impact MPG or power. But they add expense and complexity to the exhaust system with no actual benefit other than emissions control. So, if you can pass whatever state E-test you need to pass without them (or don't have any testing in your region), then there is no operational benefit to including them when designing an exhaust system.
Lastly, without any details on the vehicle in question there is no way to be sure if universal fit units would be easy to install or if the necessary mounting location is extremely size/shape specific.
However, there are certainly some high flow cat options that won't do much at all to negatively impact MPG or power. But they add expense and complexity to the exhaust system with no actual benefit other than emissions control. So, if you can pass whatever state E-test you need to pass without them (or don't have any testing in your region), then there is no operational benefit to including them when designing an exhaust system.
Lastly, without any details on the vehicle in question there is no way to be sure if universal fit units would be easy to install or if the necessary mounting location is extremely size/shape specific.
#3
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I recently installed a high flow cat in the middle of my Y-pipe with long-tube headers and an electric cut out post-cat, and I didn't notice any measurable performance loss at all with my "butt dyno", and my fear of it being too quiet were also relieved. With the cut out open, it actually sounds better now than when it was just off-road Y. Still extremely mean, just less... redneck-y? 1998 WS6 A4 TransAm ~80,000 miles.
Also, I'm not an expert, but on dual cat systems, if one is flowing free and the other still has the inside, I think that's bad for the engine because you have dramatically different flow rate / velocity in the exhaust on passenger vs. driver side. That's why I did 1 cat in the middle of the Y, and they never recommend removing just one cat if you have two. This is just what I've read.
Also, I'm not an expert, but on dual cat systems, if one is flowing free and the other still has the inside, I think that's bad for the engine because you have dramatically different flow rate / velocity in the exhaust on passenger vs. driver side. That's why I did 1 cat in the middle of the Y, and they never recommend removing just one cat if you have two. This is just what I've read.
#4
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Cats help with reducing emissions which is a good thing. Cats reduce the exhaust smell which is also a good thing. Cats are expensive and can be difficult to package which are both bad things. If you need them for inspection then you don't have a choice. If you don't have inspections then you can try both ways and go with the one that you feel better about. I run no cats, but I may add some later to cut the smell down if I ever start daily driving my TA.
#5
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Cats help with reducing emissions which is a good thing. Cats reduce the exhaust smell which is also a good thing. Cats are expensive and can be difficult to package which are both bad things. If you need them for inspection then you don't have a choice. If you don't have inspections then you can try both ways and go with the one that you feel better about. I run no cats, but I may add some later to cut the smell down if I ever start daily driving my TA.
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But that unfiltered exhaust is just so toxic, I finally got sick of it (especially with women and kids in my car) and went with the high-flow cats. Pretty pleased with it.
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IMO, the biggest subjective downside to cats is that they give any engine a more smooth, mellow sound. This significantly detracts from the traditional muscle car "cackle". But I guess the youngest generation of enthusiasts are probably used to this, and may even prefer it.
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#8
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One of my first cars was a '71 Cutlass that was, of course, catless from the factory; with a stock engine the smell was barely even noticeable to me. ~25 years later, I've owned several catless, cammed/built engine vehicles which smell much stronger, but to this day I'm still not bothered by the smell as long as the car has proper tail pipes (I could see how this might be bothersome on a daily driver with dumps though). Mrs. RPM has never complained either. I guess everyone has a different level of tolerance. I think I was about 8 years old before my parents even owned a vehicle built in the cats/smog years, guess I got used to it at a young age. ![Grin](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_grin.gif)
IMO, the biggest subjective downside to cats is that they give any engine a more smooth, mellow sound. This significantly detracts from the traditional muscle car "cackle". But I guess the youngest generation of enthusiasts are probably used to this, and may even prefer it.
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IMO, the biggest subjective downside to cats is that they give any engine a more smooth, mellow sound. This significantly detracts from the traditional muscle car "cackle". But I guess the youngest generation of enthusiasts are probably used to this, and may even prefer it.
But when I refer to toxic, I don't just mean the smell. I mean, don't catalytic converters help make exhaust less dangerous to the human body?
#9
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With my cut outs open (pre-muffler, obviously) it still sounds amazing to me with high-flow cats. It did change slightly, I guess as you call it the cackle, it doesn't let some of the slight afterfire through?
On the other hand, the original/traditional "muscle car" sound requires catless true duals with either an H-pipe or no crossover at all (even an X-pipe will cause the pitch to be higher and/or smooth the note). A couple of platforms from this era used a dual in, dual out muffler which acted as a type of crossover, but many just had independent dual systems. These true dual systems create a distinctive sort of sound (different from even an ORY) that can't be exactly replicated with cats in place. Furthermore, that undesirable "Kazoo" sound (which is typical of an ORY setup) is not something which occurs with a true dual system, regardless of cats/catless or crossover or not.
IMO, the best sound comes from no cats, true duals, H-pipe or no crossover at all, and chambered mufflers. But, of course, that's subjective.
But when I refer to toxic, I don't just mean the smell. I mean, don't catalytic converters help make exhaust less dangerous to the human body?
#10
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I grew up with old cars too so I'm not really bothered by the smell. I only notice it when I'm loading or unloading the back with the engine running. After that my clothes smell sooty for a few hours. If I was driving it to work or school the smell on my clothes would be a problem after a while, but since it's only a fun car at the moment I'm not in any hurry to spend money on cats lol
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#15
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And being ignorant of the science or reasoning behind most emissions and safety equipment on modern cars doesn't give someone the right to act like a self righteous *****.
#19
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The way to reduce smog, which is the ultimate goal of all emissions equipment, is to reduce the time an engine spends running and reduce the fuel consumption while it does run. That means reducing necessary drive time, reducing pleasure driving and reducing time spent at higher rpms where more fuel is burned. These are all things that are done on a regular basis by people who spend time posting pics of their race car on a car forum. From your post history I can promise that you release more smog in a year than I do in 5.
#20
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