Aftermarket 540i Catalytic Converter Info

DIY Forum was looking kind of weak, thought I'd add a nugget of info.

If you are looking for aftermarket Catalytic Converters on your E39 540i, here are some options:

Carsound 53005 2.25" in/out, round body, no air, $67/each: http://www.exhaustproslinc.com/carrounbodun.html

Or you could pay more for the IDENTICAL converter with a polished case, Carsound makes Magnaflow, they are the same thing.

Magnaflow 54305 2.25" in/out, round body, no air, $80/each: http://www.exhaustproslinc.com/magpolstains1.html

Make sure that you exhaust guy is very comfortable with blind welding in tight spots, otherwise make him drop the system to ensure that there are no leaks around the converters. Leaks may throw the O2 sensors off. I doubt that you will find a good welder at anyplace besides a custom exhaust shop, the guys at Midas and Minekie probably are not cut out for this job.

If you don't know of a really good local exhaust guy, here is decent place to start: http://www.magnaflow.com/03dealer.htm

So here are your choices:
- $600/side for BMW Cats + installation.
- $67/side for Carsounds + $100-$150 for installation.

I can tell you to avoid IMCO Cats in a 540i, I had a pair of IMCO High Flow Cats (75115) installed once. The drivers side converter started rattling within 3 weeks, the ceramic brick was loose from the metal casing. I went back to the shop and had Carsounds (53005) installed, like they should have had them do originally (but that’s another story). The owner was apologetic and said that he was just trying to get his customer the best value, just tipped the welder $20, otherwise no charge for the Carsounds.

IMCO Cats: http://www.imcoweb.com/

[quote=kowached]DIY Forum was looking kind of weak, thought I'd add a nugget of info.


Thanks Dave. It seems that most of the DIY posts have been going to the main section-I'm guilty of it . I am hopeful that with the new influx of DIY's from around the net we can build a significant and useful DIY section. Your E39 welcome page is a great reference and I hope to see it here.

Originally Posted by kowached

If you are looking for aftermarket Catalytic Converters on your E39 540i, here are some options:

Thx Dave. I'll be doing the CarSound's pretty soon. Hey, you have any info on people installing 2.5" inlet/outlet into our cars? Rev was telling me to choose those at one point. I've got a little more exhaust than normal leaving my car, but don't know if the 2.5" with larger custom tubing all the way back is really necessary. Let me know if you remember any discussion of that.

You could run the 2.5" converters, but everything in front of and behind the converter (until the pipes join) is 2.25". It would be easy enough to change everything behind the converter to 2.5", but I'm not sure that it would be worth it unless you increased the pipe diameter (headers?) in front of the converters. I think that M Wong (E38 RF) went with the 2.5" converters, but had trouble down the line. See if he has anything else to provide.

Have you considered measuring backpressure while under load to see where you are currently at?

Hey Guys,

I put the Carsound 53005's on my 1997 540i yesterday, i am having some misfire issues on the engine. Has anyone else used this model cat with success?

Frank