Cat or no cat?

Most of my gearhead friends keep telling my to straight pipe my car. With a resonator or a high performance/flow muffler. Cut out the annoying cat. And I agree with them, since I don't have to pass the emissions test, and I really want to do it. But before I do anything, do you guys agree with this? Opinions gladly accepted

ethically, i wouldnt, but no you dont need it and does free up some HP

even with a stock exhaust, removing the cats completely changes the tone. it'll sound better.

with a completely new straight pipe to single muffler setup, the car will be loud. it'll drone and get annoying fast.

it all comes down to opinion, neither way of deleting the cat is bad for the car. the noise level is all up to the driver. i keep my dailys exhaust stock .. because i like to hear music and people talking while im driving.

Yeah, I have been considering the cabin noise with a setup like that. Never been privileged to ride in a loud car, so I have no idea *how* annoying it can be. But I've heard that after awhile it bugs the life out of you. I'll probably go with a modest muffler that has some bite to it when you give it the gas

Running with no cats can also make Your car produce some interesting smells. On the flip side of that coin I don't think E30's came with cats in europe.

Originally Posted by Terrains

Yeah, I have been considering the cabin noise with a setup like that. Never been privileged to ride in a loud car, so I have no idea *how* annoying it can be. But I've heard that after awhile it bugs the life out of you. I'll probably go with a modest muffler that has some bite to it when you give it the gas

you dont want to find out

Originally Posted by Alfa Seltzer

Running with no cats can also make Your car produce some interesting smells. On the flip side of that coin I don't think E30's came with cats in europe.

The facelift M20 cars did and then the M40 followed around 91-92. obviously some countries the whole lot did due to emissions laws, though i cant name any countries like that. noone cared about emissions in those days

I wouldn't. You have a eta its slow.

That's true. It's certainly not fast. But after saving up some money, and fixing all the wrongs in it, I could do something about that. Most likely will never get around to it but, I can dream

i ran no cat in my mazda with a flowmaster super44, and cat in my e30 eta with the same muffler, but had 2.5" from cat back. sounds was about even, the mazda had a high tone to it, but if you kept out of the throttle, you didnt have to have the volume up too high. on the e30, if you got on it, you heard it. but only time i really noticed on the highway it was a mild tone. just a couple clicks on the radio would drown it out. now going through tunnels and under bridges, people hated me. it had such an underlying low tone that it would vibrate the car.

want a simple way to test if you "can deal with" the noise thats reversible and cheap?

get an angle grinder and cut a 1.5" by 1.5" section out of your stock exhaust about 6" before your muffler. your car will get loud. you need to realize with a straight pipe system to a "performance" muffler it will be even louder. if you don't like it, you only need $20-$40 to have a muffler shop weld a patch over the hole.

it will idle louder and even sound like its more powerful. drive it around for a week, then see if you want to deal with it being louder than that permanently.


my 325is DD has a completely stock exhaust. my sterling 325i has a stock exhaust with a hole right before the muffler. everyone thinks the sterling is modded. i'll fully admit it sounds nice when its driving and you get on it, but it drones at idle and gets annoying real quick. i can try to take a video of them next to eachother later.

or if you muffler is shot, do what steve said to the muffler. thats what happened to mine. saw a little rust on the under side, then 3 weeks later goin bout 80 the car got noticeably louder, pulled over, saw that rust turned into a hole. sounded about the same with the muffler, only with muffler was louder on start up.

I took off my cat it sounds alot more beefy i feel a bit of gain or maybe not ether way it sounds good next is a nice set of headers but i say keep stock muffler

I don't know the answers to the following questions, but I will put them out there for consideration:

Does the M20 rely on a certain amount of back pressure in order to achieve peak performance?

Will the chip need to be notified that there is no cat?

I actually have 2 cats on my car. The mechanic said my old one was done completely, and instead of removing it and replacing, he just installed another one right in front of the old one. So my exhaust system consists of 2 cats, and probably a $10 muffler. Surprised my car isn't choking on it's exhaust fumes trying to push it through all that crap.

I would keep the good one and take out the bad. Had the cat removed on a couple cars and the gas smell people smell doesn't make your car look to fancy lol

Originally Posted by Terrains

I actually have 2 cats on my car. The mechanic said my old one was done completely, and instead of removing it and replacing, he just installed another one right in front of the old one. So my exhaust system consists of 2 cats, and probably a $10 muffler. Surprised my car isn't choking on it's exhaust fumes trying to push it through all that crap.

The bad cat is prolly empty, so no harm no foul.

I'll get around to it one of these days. Not really enough spare time and it's been like 100+ Fahrenheit here with the heat index for the past 3 weeks. I'm thinking on getting a pipe that's slightly wider at the ends so I can clamp it on and just going to Advance Auto for a magnaflow muffler.

Originally Posted by markseven

I don't know the answers to the following questions, but I will put them out there for consideration:

Does the M20 rely on a certain amount of back pressure in order to achieve peak performance?

Will the chip need to be notified that there is no cat?

yes. in fact pretty much all engines do, even 2 stroke engines.

Originally Posted by Terrains

I actually have 2 cats on my car. The mechanic said my old one was done completely, and instead of removing it and replacing, he just installed another one right in front of the old one. So my exhaust system consists of 2 cats, and probably a $10 muffler. Surprised my car isn't choking on it's exhaust fumes trying to push it through all that crap.

wtf