Will it mess up the cars 02 readings or should I be good?

germans are smarter than u at making cars... leave them in

I don't want them.

This was a simple question.

Will it mess up the cars 02 readings?

Yes. The car may idle crappily and get terrible mileage. Just curious, why do you want to remove them?

Yes. The car may idle crappily and get terrible mileage. Just curious, why do you want to remove them?


They are rattling around a bit and since I run with a dealer plate, I don't need to go through emissions anyways. So I'm at a point where I don't need them so why spend the money for new ones. I know I could save some cash with the Magnaflows but why even spend that money if I don't have to?

It will mess with your o2 readings since the car has pre- and post-cat sensors.

They are rattling around a bit

It means they're going bad.

eddieb022000 is right, leave them in ... well, remove the bad ones and put in new ones, but leave the new ones in.

Also loss of power due to lack of back pressure.

Loss of power, poor mpg, worse noise, more pollution, sensor warnings.

For me just one of those would suck enough but hey, if the package deal is your thing :)

Just replace them seems to be the overall verdict

I removed them from my mustang for performance reasons, and the smell is horrible. Just on that reason, since it's a BMW that would smell like rotten eggs, I'd leave them in.

No way, catless American V8 sound and smell is :drool:

You've probably checked this already but are you sure it's not just a heat shield rattling? (I wouldn't be asking this if it hadn't happened to me on 2 cars already :))

You've probably checked this already but are you sure it's not just a heat shield rattling? (I wouldn't be asking this if it hadn't happened to me on 2 cars already :))

+1

Does anyone make O2 sims for these cars? It would be okay to run without cats if you can get around the drivability issues. You *might* run into back pressure problems but I seriously doubt it if you are running the rest of the stock exhaust system. They are plenty restrictive. Don't forget that you could end up with the deaded drone if you tinker with the exhaust. That would suck in such a nice car like these.

Why don't you try this.... take YOUR cats out and install a plain pipe. Run it for a week and get back to us. Let us know how it works. If you end up with drivability problems simply install the MF cats and be done with it. You need to take the old ones out anyway, right?

One negative not mentioned - it's illegal and harms the environment, but hell, $300 bucks is $300 bucks, screw the environment.

Seriously, spend the freakin $300 on the generic brand and be done with it.

If I were a tree hugger, I wouldnt be driving a 7 series.

One negative not mentioned - it's illegal and harms the environment, but hell, $300 bucks is $300 bucks, screw the environment.

Seriously, spend the freakin $300 on the generic brand and be done with it.

since it doesnt sink in: germans (and almost everyone else on this board) are smarter than you at making these cars...

pls kill this thread now:rolleyes

Does anyone make O2 sims for these cars? It would be okay to run without cats if you can get around the drivability issues. You *might* run into back pressure problems but I seriously doubt it if you are running the rest of the stock exhaust system. They are plenty restrictive. Don't forget that you could end up with the deaded drone if you tinker with the exhaust. That would suck in such a nice car like these.

Why don't you try this.... take YOUR cats out and install a plain pipe. Run it for a week and get back to us. Let us know how it works. If you end up with drivability problems simply install the MF cats and be done with it. You need to take the old ones out anyway, right?


Thats What I have considered doing. Punching out my old cats and running a pipe through them.

since it doesnt sink in: germans (and almost everyone else on this board) are smarter than you at making these cars...

pls kill this thread now:rolleyes


I think a lot of people may "think" they are "smarter" (not a word) than I am. Fact of the matter is, I highly doubt BMW would put converters on these cars unless the government made them do it.


I am getting decent answers from people. (giving me REAL answers) Please leave the thread.:rolleyes

If I were a tree hugger, I wouldnt be driving a 7 series.


OK, environment aside, as I am by no means a tree hugger. Let's see, you are looking to remove your cats because you don't want to spend the money on new ones. I don't get it, unless of course you are short on cash, it seems silly to want to do this. I could even see if it would improve performance, but you clearly state it is all about the money.

Lastly, what about the emissions that may leak into your car and possibly harm what looks like your son in your pic?

Edit. not trying to start a pissing match.

Will it mess up the cars 02 readings or should I be good?

Given that this was your original question, the direct answer is: Yes, there can be negatives and yes, it can mess up your o2 readings.

Yes, you can intentionally bypass them, there are all kinds of tools and gadets to help you do that, and all kinds of pros and cons.

With that in mind, you'll do what you want to do but I personally really hope that you go ahead and replace them. If you really want a dirt cheap solution, check the junk yard.

I'm definitely no tree-hugger, but I also don't pour my used oil down the storm drain. IMHO, driving a car that's supposed to have cats without them purely because of the cost or hassle of replacing them is in the same neighbourhood.

Thank you. Thats what I was looking for.


Given that this was your original question, the direct answer is: Yes, there can be negatives and yes, it can mess up your o2 readings.

Yes, you can intentionally bypass them, there are all kinds of tools and gadets to help you do that, and all kinds of pros and cons.

With that in mind, you'll do what you want to do but I personally really hope that you go ahead and replace them. If you really want a dirt cheap solution, check the junk yard.

I'm definitely no tree-hugger, but I also don't pour my used oil down the storm drain. IMHO, driving a car that's supposed to have cats without them purely because of the cost or hassle of replacing them is in the same neighbourhood.

If I were a tree hugger, I wouldnt be driving a 7 series.

Haha...damn right.

I'm a tree hugger.

Every time I fill up my E38 with gas, I plant a tree.

No way, catless American V8 sound and smell is :drool:

Don't get me wrong, the sound is fantastic. It is loud and in your face, but not exactly the sound of a refined german saloon auto.

Don't get me wrong, the sound is fantastic. It is loud and in your face, but not exactly the sound of a refined german saloon auto.
Oh I totally agree that they are completely different. I love the aggressive yet subdued (in comparison to an aggressive American sound) German V8 sound, but I am also big into American muscle.
Here's one of my favorites:
http://video.google.com/videoplay?docid=-3757928846591975316

Oh I totally agree that they are completely different. I love the aggressive yet subdued (in comparison to an aggressive American sound) German V8 sound, but I am also big into American muscle.
Here's one of my favorites:
http://video.google.com/videoplay?docid=-3757928846591975316

this is on par with what mine sounds like...hard to tell from video to real life.

http://www.youtube.com/watch?v=PDr9lxWtiuw&feature=related

I was about to buy a '98 GT last May but the sale fell through. The title was kinda fishy, didn't seem legit. It was a shame, that car was LOUD.

Old school muscle is cool but within a year, I will be in the market for a GN or typhoon/syclone.


And it won't have cats!!:D

Get an '87 GN, the best and final year.

Get an '87 GN, the best and final year.


I would be happy with even a clean T type.

T type's are nice too. Imagine finding a GNX :drool:

T type's are nice too. Imagine finding a GNX :drool:

A good friend of mine has one with 6,000 miles on it!!:eek:


It will be hitting Ebay shortly. The car is like new.

haha, the GN... I keep looking at my aunt's park avenue and wonder how in the hell buick came out with a car like the GN.

Remus Exhaust! http://www.youtube.com/watch?v=xll6ZjscopE

I'm a tree hugger.

Every time I fill up my E38 with gas, I plant a tree.so how is the amazon doing these days?

Just remove and tie up (dont disconnect)the post-cat o2's from the exhaust and it works like a 02 simulator. The post-cat usually just needs to register a difference between it and the pre-cat o2 sensors. Also its been tried and works.

By who? Did you do this? link to a thread?


Just remove and tie up (dont disconnect)the post-cat o2's from the exhaust and it works like a 02 simulator. The post-cat usually just needs to register a difference between it and the pre-cat o2 sensors. Also its been tried and works.