decatting the M5

[M5V8 337]

forgive if we have covered this before...

i'm thinking about decat - in the M5. Just remove and replace with straight pipes.

I'm okay with the rest of the system, rear cans have already been replaced.

Leaving the sensors in so not to produce any OBC errors I have spaced out the post cat 02's

before I go ahead...

any pro's / con's I haven't considered?

Seems plenty have done this before with good power / sound improvements.

Edited July 4, 2013 by M5V8

[jeffbebe 1559]

i'm thinking about decat - in the M5.

Leaving the sensors in so not to produce any OBC errors I have spaced out the post cat 02's

before I go ahead...

any pro's / con's I haven't considered?

any recommendations for a good place in wtgn?

I did it on my 528i and definitely noticed a slight improvement in performance though you probably need a proper tune to get the most benefit. It was a lot noisier inside the car without the cats but that can be a good thing!

I guess potential OBC errors and more pollution are the biggest cons. Mine did pump out more smoke in lower gears after de-cat.

Edited July 4, 2013 by jeffbebe

[M5V8 337]

cheers julian. you didn't have post cat 02 sensors tho?

can anyone comment on the OBC err side? will it just throw low level codes or is there a possibility of engine check light.

I wont bother if there's a chance of issues.

[smiddy 76]

Post cat sensors record temperture differance between manifold sensor. To remove cats may cause mixture to run lean.

There may be cat delete options available in tuning software out there.

High flow cats may be better option.

[jeffbebe 1559]

Post cat sensors record temperture differance between manifold sensor. To remove cats may cause mixture to run lean.

There may be cat delete options available in tuning software out there.

High flow cats may be better option.

I think Josh (hybrid) mentioned that you can remap ECU to work without cats but I agree with Wayne - I'd definitely go with high flow cats if I was to do again.

[M5V8 337]

okay cheers team.

[hybrid 1039]

Its not exactly remapping. More uploading a non cat program such as one from SA.

A quick database search says it is possible.

For vehicles with without catalytic converter or Data record without EOBD

01 EXCH control unit DME programmed MSS 52/ FLASH 1 09/2000 12147837959

[Michael. 2312]

Aside from the issues above, I would also put in some resonators in place, maybe a pair of small stainless magnaflow 4" round mufflers just to avoid getting any rattles in the rest of the stock system which could happen, Cats do tend to suppress some noise so they actually end up like small mufflers.

It could sound ok with out them, giving a bit more rumble (which would be good), but it could also make the rest of the mid section or rear mufflers get some nasty rattles, drones or 'twang' notes.

[HELLBM 1530]

Have taken out the cats on my S62/m3 conversion. Using the defoulers I sent you will allows for a sniff of gas to occur. My result-no more post cat oxy sensor fault codes and an awesome sound.

[M5V8 337]

Have taken out the cats on my S62/m3 conversion. Using the defoulers I sent you will allows for a sniff of gas to occur. My result-no more post cat oxy sensor fault codes and an awesome sound.

Are you running the standard NZ ECU Ray?

& you replaced with just straight pipe? There's no legal requirement to run them is there.

Edited July 4, 2013 by M5V8

[HELLBM 1530]

Are you running the standard NZ ECU Ray?

& you replaced with just straight pipe? There's no legal requirement to run them is there.

Yes standard NZ ecu recoded to SA non cat. Flick me an email and I`ll reply with pics of exhaust.

[jeffbebe 1559]

Yes standard NZ ecu recoded to SA non cat. Flick me an email and I`ll reply with pics of exhaust.

Hey Ray, I'm interested in this. There's a hole in one of the cats on my 540 so I've been debating what to do. Was planning to save for an exhaust system overhaul - headers, high flow cats and muffler - but if a cat delete isn't a massive pain with the o2 sensors I might do that as the high flow cats are muchos expensive! Will drop by and see you in the next week or so.

[jeffbebe 1559]

Hey Darren. Did you go ahead with this on the M5? Exhaust system is on my list and moving up the list as other planned mods (tranny s/w, stage 2 tune) will void my mechanical warranty. There's a hole in one of my cats which I suspect is causing some minor performance issues and I can't really afford to replace, so thinking of removing instead.

Catching up with Ray next week anyway, so will ask the sage for a bit of advice on the matter.

[Tristan 338]

Hey Darren. Did you go ahead with this on the M5? Exhaust system is on my list and moving up the list as other planned mods (tranny s/w, stage 2 tune) will void my mechanical warranty. There's a hole in one of my cats which I suspect is causing some minor performance issues and I can't really afford to replace, so thinking of removing instead.

Catching up with Ray next week anyway, so will ask the sage for a bit of advice on the matter.

Hi Julian

Who's your warranty with and have they confirmed that exhaust mods won't affect it?

[jeffbebe 1559]

Hi Julian

Who's your warranty with and have they confirmed that exhaust mods won't affect it?

Insurance is with these guys - haven't confirmed decat procedure is okay yet, just that trans upgrade and stage 2 tune is NOT!

They may say no, anything to avoid paying out! That said, the most they'll pay on a 13 year old car is $2.5K for repairs anyway, so if it's something catastrophic - head gasket, transmission, etc - it ain't gonna cut it.

Edited August 28, 2013 by jeffbebe

[M5V8 337]

Hey Darren. Did you go ahead with this on the M5? Exhaust system is on my list and moving up the list as other planned mods (tranny s/w, stage 2 tune) will void my mechanical warranty. There's a hole in one of my cats which I suspect is causing some minor performance issues and I can't really afford to replace, so thinking of removing instead.

Catching up with Ray next week anyway, so will ask the sage for a bit of advice on the matter.

I decided against it when weighing up having to re-program the ECU to run without. I don't have any cat issues currently but started sounding too much hassle for what was just a few extra hp gains.

Might reconsider if I ever get her upto auckland for a ecu re-tune. (if that ever happens)

let me know how you get on tho

[jeffbebe 1559]

I decided against it when weighing up having to re-program the ECU to run without. I don't have any cat issues currently but started sounding too much hassle for what was just a few extra hp gains.

Might reconsider if I ever get her upto auckland for a ecu re-tune. (if that ever happens)

let me know how you get on tho

Will do. If it's a simple re-code that Ray can do, it might not be too pricey. A tune starts getting into the 'nice to have' category. I'm not really doing it for HP gain, more because the holey cat is likely causing some issues and only going to get worse and new cats are expensive!!

Edited August 28, 2013 by jeffbebe

[yng_750 247]

turners offered me $1200 of mechanical insurance for $600 per year but excess was going to be $900 per issue

[jeffbebe 1559]

turners offered me $1200 of mechanical insurance for $600 per year but excess was going to be $900 per issue

Good deal

[*Glenn* 854]

Cats are not covered by insurance companies. Dogs are though... they'll fix most problems a dog has with an excess for each dog problem

[antil33t 90]

that sounds like cat racisism.

[Phil-540i 166]

Cats are not covered by insurance companies. Dogs are though... they'll fix most problems a dog has with an excess for each dog problem

I want........................................what he's smoking / drinking.......................

Cracking up bigtime..........

On a serious note - hows my electronics gonna handle decating a e34 V8 - no problems or ecu reflash needed??

[*Glenn* 854]

I want........................................what he's smoking / drinking.......................

Cracking up bigtime..........

On a serious note - hows my electronics gonna handle decating a e34 V8 - no problems or ecu reflash needed??

I don' t smoke.. gave up 3.00 am 10/9/2010 and I drink Lion red.. I've had three tonight... 1 when I posted

[_ethrty-Andy_ 2122]

sometimes i wish i could come up with sh*t like that when i have had one beer. Would save a lot of money

[Tristan 338]

Cats are not covered by insurance companies. Dogs are though... they'll fix most problems a dog has with an excess for each dog problem

Funny story about cats - My cousin didn't have cat insurance and when it got hit by a car they had to fork out $8k for cat surgeries. Thought maybe I should get cat insurance... Didn't..

Now my cat is diabetic, needs insulin twice a day, costs a fortune in medical bills and insulin

I don' t smoke.. gave up 3.00 am 10/9/2010 and I drink Lion red.. I've had three tonight... 1 when I posted

Damn well done, Glenn. I quit late 2011 with inspiration from your thread and my girl. Also 'Cold Turkey'.

----

ONT:

I'm thinking of deleting the secondary cats in the E92 (Woolf Mufflers) and possibly a custom cat back.

Their prices are pretty reasonable! Apparently there are some good gains from the E92 exhausts.

I should also double check with the warranty company...