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Catalytic Conveter 1997 540i

2K views 29 replies 13 participants last post by  chivas 
#1 ·
Has anyone tried any after market Catalytic Conveters on a 540i? Was wondering if they had a positive experence?

Also has anyone tried any methord of cleaning them that worked?

Thanks,
Frank
 
#2 ·
There are a lot of posts about this here and on other boards. Results have been mixed at best, at least when it comes to getting the "Check Engine" light and "Cat Efficiency Error" code to stay away. Not a huge deal if your state doesn't do emissions testing, but not a good thing if the opposite is true, in places like California.

Page FRANKA on this board - I think he went through this whole drill - replacing with aftermarkets and eventually removing them and going back to OEM's.
 
#3 · (Edited)
Swapped out the OEM for Magnaflow units (CA compliant OBDII units NOT the high flow versions). I believe the part number was 43005. They have been in my 98 540i6 for eight months now - now CEL and I just passed Missouri's emissions test (they just check the OBDII).

But it would be interesting to hear Franka's experiences...
 
#4 ·
Cleaning a catalytic converter, are you serious?

Short of buying new oem, you might try having them cut open, and new cores installed. This place does it, and is EPA/CARB certified:
http://www.millercat.com/index.html

I notice they also sell direct replacemens for many BMW models.
 
#5 ·
Thanks for all the info, One of my cats is so clogged the engine wont run as it cant breath. I removed the front O2 Sensor just to let the engine breath until i get them swapped out with Magnaflow. I hope i dont regret installing them. Has anyone tried hollowing their cats out?

Frank
 
#13 ·
Thanks for all the info, One of my cats is so clogged the engine wont run as it cant breath. I removed the front O2 Sensor just to let the engine breath until i get them swapped out with Magnaflow. I hope i dont regret installing them. Has anyone tried hollowing their cats out?

Frank
This might be a n00b question, but could you explain the concept behind that? Why would you do that and why does that make a difference? Also, my 540 has a bad cat on bank 1, would removing my O2 sensor improve my performance until I can get a new cat?
 
#6 ·
I've got a set of Magnaflow 94005's on mine, and they work PERFECT. No error lights or anything. I am not sure if they meet emissions requirements, as i'm not subject to emissions testing where I live.
 
#7 ·
Sounds good thanks for the info, Just an FYI i read an article that you can clean these out by soaking them for 8 hours in citris acid, I AM SERIOUS.
 
#8 ·
i need some cats badly....which one should i get ?? 43005 or magnaflow high-flow cats ??

if anyone using high-flow cats from magnaflow.....which model ??

i need something flow better but not too bad as No-cats,i am tired of no-cats and lossing all the low end torque and power and lost to a 528i from standstill......
 
#10 ·
Welding TIG or MIG - Magnaflow

Is there any advatage to having MIG or TIG welding for Cats? My local guy does MIG.

Thanks,
Frank
 
#12 ·
Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

- Adapted from Thomas V.
 
#14 ·
I had a lot of trouble with aftermarket cats that my BMW dealer TOLD me to use. Long story. Dealer even helped to tune the car to work with them. Would work for a while then CEL. I eventually got a good price on OEM from the dealer since they were implicit in the problem.

Even if you can get a good pair of cats that will not throw CEL the dealers and indys will forever be pointing their finger at them claiming they are the source of all your problems.
They will even claim they are the souce of your problems with your divorced wife, or not yet divorced wife.
 
#16 ·
I know of a handful of people running magnaflow cats on M62 engined cars, a buddy of mine with a 740i as well as a friend with a 540i - neither have had issues with them. DEC makes lower cost straight OEM replacements that do not require welding but they're still pretty spendy. One thing to note about the magnaflows though is that I'm pretty sure they do not meet Cali emissions standards.

I'm not sure how restrictive the stock cats are though and I haven't heard of any performance improvements from running without them or freer flowing ones. Another big bottleneck is the stock resonator - people switching to aftermarket setups there generally seem do seem to lose some low-end performance.
 
#18 ·
I'm not sure how restrictive the stock cats are though and I haven't heard of any performance improvements from running without them or freer flowing ones. Another big bottleneck is the stock resonator - people switching to aftermarket setups there generally seem do seem to lose some low-end performance.
When I was having aftermarket cat problems I heard from a performance shop that they felt the OEM cats were good flowing and that there was no point in replacing them for performance alone.

And to sex69, if you can get more assurance against throwing codes for a mere $ 100 you should be all over that.
 
#17 ·
43005 or 94005

bimmerd00d -

Hey - How long have you had the 94005's on and are there still no CEL's.

I am torn between the 94005 and 43005.

Seems like the 94005 would work but the 43005 which is rated for cal. may be more efficient and last longer without throwing codes.

Don't know if the extra $100 ea. is worth it or not.

Thanks,
 
#19 ·
Hey I Put the new Magnaflow 53005 cats on my 1997 540i today, man i love them. Lets see if the Engine Lights stays off, :)

Frank
 
#21 ·
FrankTea

Here's what I used when I owned my 540...... Below is an old thread I posted on.

I'd suggest looking for a good custom muffler shop for the install. I was going to go with Midas at first, but they gave me a quote of $640 without dropping the exhaust system to do the welding. The workspace is way too cramped in the CAT area to attempt to weld without dropping the entire system to assure a good weld without leaks. Plus, I've heard in certain areas (mainly Cali.) they (Midas and Meineke) don't like to install aftermarket CATs that aren't ordered through them. I finally found a good custom exhaust shop in my area and they did an excellent job. Dropped the exhaust system and welded both CATS for $200. I'll definitely go back to them when I decided on exhaust. The 43005's are pretty big CATs so you need someone to position them properly in the small area under the car so they don't hang too low. After the CAT replacement I'm in love with the car again. No hesitation...quick acceleration and even sounds more throatier as the CATs break in. I've even put off the exhaust mod for now...

Also, for 2 of the OBD II compliant 43005's it's $180 for each CAT. Haven't seen them that much cheaper anywhere yet, but it's a great alternative than the $1k or more for one OEM CAT.
 
#22 ·
Thanks for the info, i read others have used the 53005's on their 540i's. If i have issues i try the 43005's.

Has anyone on here used the 53005's on their 540i?

Frank
 
#27 ·
Not to answer for Dan, but the 53005's are too small. They can't hold up to the heat generated by the V8. Numerous 540 owners have tried the 53005's and most have been unsuccessful. Haven't heard that many success stories to say they're okay to use. Eventually they will throw a code relating to the CATS. I took the advice from another board member and went with the 43005's. After installation and a couple thousand miles there was no CEL. Car was finally breathing and responding like it used to. Even sounded better. You can try to go with the 53005's(i believe they are cheaper $) but I'd suggest a custom shop doing the welding and cross your fingers that it's not money wasted a few hundred miles later. Just my .02.
 
#28 ·
I got the 53005's on my car as of yesterday, i am getting mis fires because of this.

I spoke with Magnaflow they recommend 94004's as i live in NY and not CA. Do you think its a safe bet going with 94004's?

Thanks,
Frabj
 
#29 ·
I got the 53005's on my car as of yesterday, i am getting mis fires because of this.

I spoke with Magnaflow they recommend 94004's as i live in NY and not CA. Do you think its a safe bet going with 94004's?

Thanks,
Frank
 
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