questions about decat on exhaust

[Jakkals_F30]

Ecede told me a few months back around 4k...

CT guys is around 5k

Exhaust done and from what i heard is we will need the high flow cats

That's how i got to 8K :thumbs:

 

[abmi0000]

i thought you just cut them out and welded in a piece of pipe?

aka mini cats. Some cars, like mine specifically, require them because of an extra set of sensors further up on the branches. You can't have all the sensors (so I have been advised) receive the same flow and obviously same values as this could end up with over fueling issues that can't be re-mediated properly on the remapping either. These cats are usually between R400-R500 each and I needed 2 of them

 

[andrewbuch]

Unlucky for you guys

I just needed a piece of pipe.. Total cost of my Decat was R250

 

[abmi0000]

Unlucky for you guys

I just needed a piece of pipe.. Total cost of my Decat was R250

Lucky you. The labour time on my car was around 3 hours due to the placement of them. Again, everything on my car's exhaust is x 2

I paid R1600 for the decat, 2 x hi flo cats and labour to fit twin tails at the same time. Based on the level of difficulty, I certainly got out ok

 

[Baron]

Which places do you guys recommend?

Powerflo is probably the most talked about on this forum, but they've also had mixed reviews (eg they blew one guys ECU by grounding the welding electrode to the body of the car and not the exhaust).

Cheetah exhaust wanted R4800 and 3 days to do a E46 325i decat :/

TNT's website is so unbelievably shockingly bad that they dont even have a street address on it, and it makes me not want to trust them with my car...

 

[SP33DYV]

I really don't know if it's worth the effort and the money.
:sorry:

 

[Baron]

My exhaust needs to be fixed in any case, plus my cats are probably blocked, plus there's no point in doing software if you dont decat...

Anyone have recommendations?

 

[SP33DYV]

My exhaust needs to be fixed in any case, plus my cats are probably blocked, plus there's no point in doing software if you dont decat...

Anyone have recommendations?

SW will only give marginal gains on a NA car.
Have a look at this thread:
We've done some scientific tests

 

[abmi0000]

My exhaust needs to be fixed in any case, plus my cats are probably blocked, plus there's no point in doing software if you dont decat...

Anyone have recommendations?

SW will only give marginal gains on a NA car.
Have a look at this thread:
We've done some scientific tests

On non M cars, yes. There are decent gains on the M cars for some reason.

 

[SP33DYV]

My exhaust needs to be fixed in any case, plus my cats are probably blocked, plus there's no point in doing software if you dont decat...

Anyone have recommendations?

SW will only give marginal gains on a NA car.
Have a look at this thread:
We've done some scientific tests

On non M cars, yes. There are decent gains on the M cars for some reason.

That is debatable. I've heard of NA M cars that lost power and torque after they had someone fiddle with the 'zorsts and SW. Especially the e46 M3.

 

[abmi0000]

My exhaust needs to be fixed in any case, plus my cats are probably blocked, plus there's no point in doing software if you dont decat...

Anyone have recommendations?

SW will only give marginal gains on a NA car.
Have a look at this thread:
We've done some scientific tests

On non M cars, yes. There are decent gains on the M cars for some reason.

That is debatable. I've heard of NA M cars that lost power and torque after they had someone fiddle with the 'zorsts and SW. Especially the e46 M3.

Could also be an issue resulting from poor tuning :dunno:

Anyway, if there are hardware changes that affect fueling, etc, the map should be redone according to me to get the car to run smooth again, irrespective of vast power expectations.

 

[Baron]

@SP33DYV:

Have you dynoed that stock 325i (if it's your car)?
Would be interesting to compare it to Cois's dyno specs after his SW and Exhaust see how much of a difference it made..

 

[SP33DYV]

The M cars are already "tuned", hence it is not that easy to extract more power from them by fiddling with the SW and/or the exhaust system. You really need to know what you are doing. It should be easier with the non M cars, but that has also been proven not to be of great gain.
This being said, the exhaust tone can definitely be enhanced.:thumbs:

If you want a noticeable increase in power you need to start changing more hardware (ie Schrick cams) and enhance the flow inside the ports of the head. This will definitely increase the power of the motor.

---

@SP33DYV:

Have you dynoed that stock 325i (if it's your car)?
Would be interesting to compare it to Cois's dyno specs after his SW and Exhaust see how much of a difference it made..

We will need to take both cars on the same day to the same dyno to make an accurate comparison.

 

[Andy1GP]

what is a hi flo cat?

i thought you just cut them out and welded in a piece of pipe?

Abmi Cleared up most of your questions already. Welding in a pice of pipe aka straight pipe. The car then sounds weird, louder but not nicer. There is no resonance to it. Cutting/removing the innards is better regarding sound.

Ideal would be to get another set of exhaust manifolds from a similar car then you can take that and have it gutted. (Split the boxes and remove the honeycomb etc...) Then just bolt on and off the old/new one. That way you can revert to 100% stock without having to re weld.

From the pics - realoem you only have cats on your exh manifold. And then a primary and secondary silencer.

Here are your cats
http://www.realoem.com/bmw/partgrp.do?model=VH16&mospid=50150&hg=18&fg=10

Your exhaust




This is what a "cat fooler" looks like. It contains platinum/stainless so that your ecu doesn't pick up an error from emissions.


This is another pic of a "cat fooler" despite what the pic says


A mini cat is exactly that, another catalytic converter just smaller with less restriction. Similar to a high flow cat. They are engineered to pass emissions and provide performance.

---

I reckon expect to pay R2000-R2500 to have them removed and either mini cats or foolers fitted. They quoted me R850 per cat fooler. So if Abmi can get those mini cats for R500 odd its cheap.

Lots of PITA for little gain. For R4k you can have decent software loaded on your car and that would probably make similar if not more gains.

 

[SP33DYV]

what is a hi flo cat?

i thought you just cut them out and welded in a piece of pipe?

Abmi Cleared up most of your questions already. Welding in a pice of pipe aka straight pipe. The car then sounds weird, louder but not nicer. There is no resonance to it. Cutting/removing the innards is better regarding sound.

Ideal would be to get another set of exhaust manifolds from a similar car then you can take that and have it gutted. (Split the boxes and remove the honeycomb etc...) Then just bolt on and off the old/new one. That way you can revert to 100% stock without having to re weld.

From the pics - realoem you only have cats on your exh manifold. And then a primary and secondary silencer.

Here are your cats
http://www.realoem.com/bmw/partgrp.do?model=VH16&mospid=50150&hg=18&fg=10

Your exhaust




This is what a "cat fooler" looks like. It contains platinum/stainless so that your ecu doesn't pick up an error from emissions.


This is another pic of a "cat fooler" despite what the pic says


A mini cat is exactly that, another catalytic converter just smaller with less restriction. Similar to a high flow cat. They are engineered to pass emissions and provide performance.

---

I reckon expect to pay R2000-R2500 to have them removed and either mini cats or foolers fitted. They quoted me R850 per cat fooler. So if Abmi can get those mini cats for R500 odd its cheap.

Lots of PITA for little gain. For R4k you can have decent software loaded on your car and that would probably make similar if not more gains.

---

HERR, don't do it. Rather put the money away for maintenance issues. My 325i is now almost 9 years old and I have not seen the need to do this.

 

[m20boy]

can 1 not fit an xpipe in place of just a straight pipe ?

 

[abmi0000]

can 1 not fit an xpipe in place of just a straight pipe ?

AFAIK, they are usually designed that way for V motors.

 

[m0lt3n]

I think 1 and maybe 2k for a better exhaust note is worth it!

On my e36 I replaced boxes and the cat with standard freeflow boxes. cant you do that as well as the cat fooler on an e90?

On my e90 I intend to just replace with a downpipe and use the fooler. But its a diesel...

 

[SP33DYV]

I think 1 and maybe 2k for a better exhaust note is worth it!

On my e36 I replaced boxes and the cat with standard freeflow boxes. cant you do that as well as the cat fooler on an e90?

On my e90 I intend to just replace with a downpipe and use the fooler. But its a diesel...

It is a total different story for turbo charged cars.

 

[moe essa]

@herr Bmw not worth it my E46 was decatted and had performance box the issues i had and errors that the Ecu picked up was i nightmare not to mention the car was burning too rich i went to bemows and got the original exhaust system with the CAT and fitted it, never had a issue ever since my wife always says if u want to modify a car buy a VTEC or Runx BMWs are fussy one small change and all hell brakes loose "If its not broken dont fix it"