How to go "Catless"?

[Oshin02]

Hey guys! I was wondering if anyone knew how to eliminate the catalytic converters without damaging/hurting anything else on my car. Also, is this all that beneficial? Thanks!

[Nt_loader]

The cats are built into the headers, if you want to remove the cats, replace your headers. I personally went supersprint headers :thumbup:

[Will ZCPM3]

heres a quote taken from a thread i posted earlier on this. supposedly the o2 sensors do more then most think:

You lose part of the DMEs ability to tune the motor.

The main purpose of the 2 post cat Lamda sensors is to check and make sure that the cats are there and functioning, but the DME also uses the readings from all 4 Lamdas to adjust the A/F trims and timing for the motor.

Going to a straight pipe will through a CE light if you don't add 02 simulators, but adding them lies to the DME, thus you have taken away some of it's ability to adjust correctly.

I have the Super Sprint headers / cat combo and the cats are a super high flowing design so you are not giving up anything going that route. Doing the straight pipe ads the extra work of setting up 2 simulators, limits the DMEs ablilty to correctly adjust fuel and timing, and emmissions blah blah blah.

[beanfree]

I thought that if you remove the cats then your check engine light will be on.
In order to remove the check engine light you now have to get cats and attach them further down. Do a search and you will find a lot of information.

[Nt_loader]

I get a check engine light every 300 - 400 miles

[Oshin02]

so I guess going catless isn't a positive, correct?

[omes]

so I guess going catless isn't a positive, correct?

Well I definitely agree that going catless has it's drawbacks.
The ECU looks at the O2 sensors and adjust Longterm Fuel Trim (LTFT) and Short Term Fuel Trim (STFT). From this it then determines fuel mixture (your LTFT and STFT), it will try to richen the fuel mixture. The ECU will pull ignition timing it sees low cat effieciency and the rich mixture.

Lots are running without cats, they get a CEL every now and again but I personally thing that any gains ASSUMED from running without cats are nullified by the ECU adapting/compensating.

O2 Sims are possible, I actually bought a set after much research but my local tuning shop is in close contact with the engineers at Dinan suggested to just run with Cats as the our O2's switch and data analyzed by the ECU at a very high frequency.

My opinion ...spend the dough on a set of high flow cats, and ensure proper installation/extension of your O2 wiring harnesses, trust a good exhaust shop. You don't have to spend the arm and a leg for the Supersprint or RD sport ones if you aren't concerned about polished stainless, just buy a couple of single cherry bomb cats and have them welded in.

[Nt_loader]

Sorry guys but I dont feel any loss of power :thanks:

[Oshin02]

Thanks a lot guys, this really helped! :D

[SB_330xi]

Hi, I went catless myself (Supersprint headers) and installed the 2nd catless exhaust part too. I went to our local BMW dealer, and they uploaded cat-less DME software. Afterwards - I removed the two end-most sensors alltogether.

So - that's the best way to go....

sergey

330xi, ESS, Supersprint headers, UUC stuff :)

[thekubiaks]

Hi, I went catless myself (Supersprint headers) and installed the 2nd catless exhaust part too. I went to our local BMW dealer, and they uploaded cat-less DME software. Afterwards - I removed the two end-most sensors alltogether.

So - that's the best way to go....

sergey

330xi, ESS, Supersprint headers, UUC stuff :)

Sergei,
If you have an ESS S/C, then ESS rewrote the DME software. I didn't know that BMW could upload (or even wrote) cat-less software for the DME. And, that BMW could upload it without overwriting ESS's S/C software. So, if this is possible, that is excellent. Please explain a little further if your ESS is working with no CEL's and you are running cat-less.. Thanks ! :D

[SB_330xi]

Sergei,
If you have an ESS S/C, then ESS rewrote the DME software. I didn't know that BMW could upload (or even wrote) cat-less software for the DME. And, that BMW could upload it without overwriting ESS's S/C software. So, if this is possible, that is excellent. Please explain a little further if your ESS is working with no CEL's and you are running cat-less.. Thanks ! :D

Cat-less BMWs are a norm around here - we're much easier on the eco-regulations. Here is what I've done with my car:

-6 months before the ESS, I installed the SS headers. We've decided to remove the 2 outer oxygen sensors altogether. then immediately the CEL turned on (no surprise there), and I drove to a local dealer, and they uploaded a special NOKAT software. the CEL switched off, and the car drove much much much stonger. I guess that it's a special BMW software for the local market. We sometimes have horrible fuel, and cats die quickly.

-a month ago i installed the ESS, they did remove the DME and upload their stuff, but like Asbjorn said - they are not rewriting the whole DME, they are only changing fuel maps, rev maps, etc.

Sergey

[thekubiaks]

Cat-less BMWs are a norm around here - we're much easier on the eco-regulations. Here is what I've done with my car:

-6 months before the ESS, I installed the SS headers. We've decided to remove the 2 outer oxygen sensors altogether. then immediately the CEL turned on (no surprise there), and I drove to a local dealer, and they uploaded a special NOKAT software. the CEL switched off, and the car drove much much much stonger. I guess that it's a special BMW software for the local market. We sometimes have horrible fuel, and cats die quickly.

-a month ago i installed the ESS, they did remove the DME and upload their stuff, but like Asbjorn said - they are not rewriting the whole DME, they are only changing fuel maps, rev maps, etc.

Sergey

Thanks for the reply Sergey, I'd sure like to add SS headers and go cat-less but I'd bet I can't get that cat-less DME program. I'll check into that. Have you had a chance to dyno your car?? If so, how did you do?? Thanks!!

[vmwerks]

After my 40.2 DME upgrade and DIS valve replacement I no longer get a SES light. It used to come on every 400 miles or so as stated in an earlier post. While in the garage I can smell that my exhaust is "rich"*, I chalk it up to the lack of cats and subsequent unaltered exhaust gasses. The rear O2 sensors will throw the code since they are measuring the same output as the front senssors, thereby folling the car that the cats are bad. The rear sensors do not affect driveability, and only throw a diag code. I do not recommend running without cats. As soon as I get the shop open I am investing in a set of SS units....


I am not saying that the car is running rich.

[SB_330xi]

Thanks for the reply Sergey, I'd sure like to add SS headers and go cat-less but I'd bet I can't get that cat-less DME program. I'll check into that. Have you had a chance to dyno your car?? If so, how did you do?? Thanks!!

I dynoed a week ago. Peak numbers at the wheels were HP 287, torque 364. The outside temp was very high, and I'm a bit disappointed with the results. Too bad I can't install an IC into my XI, I think that i am also getting some loss of power as the car heats up. I'm planning to install an M3 oil cooler soon, maybe that will drop the overall temp down a bit.

I'm driving around with a reach/lean gauge, i'm normally at stoich 14, and at wot it drops to a slightly rich 12.5

sergey