cataliytic convertors

[mfcsw]

Hi everyone, been looking through the posts and carnt find much info on the subject of swapping out front and mid cats on the bmw1m coupe.
I don't want the hassle of having to put the cats back in for the yearly MOT so
For me de-cat front pipes are not really an option,I am after any advice people have on the best compromise of differant mixes of cell ratio cats that will still pass the MOT and not give any warning lights or error codes.maybe putting 100 cell cats in front and middle ?would that work or 200cell front and none in the mids,
Any advice would be great fully received
Many thanksk

[Em/1]

I think you want to keep the front cats cuz they are high flow anyway; just get Maddad mid (eliminates mid cats but looks pretty much stock) and will sound better and go faster. Will never throw a code with that set-up.

[mfcsw]

yes I tried this route with either maddad or berk but carnt get anywhere that will ship to uk £800 postage is to much for me to justify , was trying a different option but you are probably right in your surgestion that removing the mids is the way to go many thanks for your input

[GAZ 345]

a n55 pipe from bmw will delete the mid cats

http://www.1addicts.com/forums/showthread.php?t=797160

[135Pats]

Are you planning on running a more aggressive tune? If not, there’s really not much of a reason to delete the primary cats, or put another way it’s probably not worth the hassle and cost. FBO N54s without a tune dyno at somewhere in the neighborhood of 300whp, granted your 1M is running more aggressive mapping, but it still it tapped out below 15psi (someone please correct me if I am mistaken). At that type of boost, IMO the upside of downpipes isn’t really going to be realized, and as you pointed out they are not without flaws (smell, smoke, noise for some people, rasp, cost of installation). There does not appear to be a consensus on just how “high-flow” the OE downpipes are for the 1m, they do appear to be less restrictive, but I haven’t heard of anyone running a true FBO type tune/map with those downpipes on.

Long story short: If you don’t plan on running a tune to take advantage of what catless downpipes offer, there’s little reason to switch. Use the money towards a better FMIC, which is totally lacking from the factory on all N54s. In the UK the advantages might be mitigated, but during the summer months your car will thank you.

[robertm]

What exactly is done for the yearly 'MOT'? If they just plug into the OBD II port then you can remove the primary cats. Just need to install an O2 simulator to fool the computer into thinking all is well. Note, the engine doesn't make any changes based on the post cat O2 sensors. They are solely there for emissions purposes.

If the MOT includes a snif test or getting the car up in the air to physically inspect then you will be out of luck.

As someone else mentioned above, level of tune you want will better help to decide which is the best DP option for your car.

[mfcsw]

I am running a forge intercooler and dms tune at 432bhp don't know what boost is at still waiting on my gauge to arrive , the mot is visual and sniff test as long as your under co2 level they will pass it , n55 is an option but that still has the resonator in it I think ,did fancy the maddads but as above not prepared to pay postage