E46 330i Decat

Bavs108

///Member
I finally took the plunge and had my car Decatted last week thanks to German Technik in EL:rollsmile: I had all 4 cats removed, 2 in the manifolds and the 2 mid cats. The pipes were cut open, cats removed and welded back together so everything still looks stock.

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After a week of driving catless I must say the difference in terms of performance before and after is night and day. The car is much more responsive throughout the rev range, but more especially in the lower rev range. The car overall feels a lot smoother and accelerates a bit faster off the line. I would be really interested to see what sort of gains I've gotten out of this on a dyno.

Interestingly enough we noticed that the post cat sensors on my car are blanked off for some reason, I only have pre cat sensors before the manifold cats so it hasn't stored any fault codes or brought up the engine light. The first day or 2 after the cats were removed it did have a bit of a rough idle, not enough to stall though, but that was due to the ECU adapting because we reset all the adaptations after decatting so it just needed some time to adjust.

In terms of fuel consumption I think it's roughly the same if not a tad better than before under the same conditions, but I think it's still too early to tell if there's a significant difference. I will update on that after 2 or 3 tanks.

I'm told that the car sounds really nice outside, but I personally find it sounds very raspy above 3000rpm in the cabin with the windows down. With the windows up I don't hear it at all. I should maybe get someone to drive my car so that I can hear for myself how it sounds:rollsmile:

All in all I think it's the best money I spent on the car and would definitely recommend it to get some extra power and responsiveness out of your car:rollsmile:

Big thanks to Yuben for the advice off forum:thumbs:
 

KPM3_30

Moderator
Staff member
Great stuff Bavs. I'll be doing this and maybe adding an after market back box :thumbs:
 

Bavs108

///Member
It was done by German Technik in East London. Their workmanship and attention to detail is very impressive:idea:
 

Bavs108

///Member
It has a tinny/raspy sound after 3000rpm kind of like an M3 but she doesn't scream as loud:rollsmile: Below 3000rpm there is a bit of a rasp but it sounds more or less like it did before. I will try to take a video later although I may need some help uploading it:flyfun:

To be honest my intention with this mod was more for the sound. I was not expecting such a big improvement performance wise. I think the biggest restriction in the system are those manifold cats. I did quite a bit of research before going ahead with this and read of people getting little to no improvements in performance, but I think that's due to people removing just the mid cats, because they're the easiest to remove, then expecting big improvements and end up disappointed.
 

moranor@axis

///Member
Official Advertiser
hollowing out the cat cases is not good in terms of flow dynamics...

the massive increase in pipe diameter kills the exhaust gas velocity this is bad for performance... you will get more out of this if you fitted pipe the same size as the rest of the system...

anyone else considering this should cut the pipe before and after the cats and use pipe to join :)

a resonator can be used to kill rasp in place of the secondary cats
 

Yuben

Senior Moderator
Staff member
The strange thing is that a supposedly reputable company like Van Der Linde did the exactly same thing on the mainfold cats like Bavs car on Sankukuers 330.
 

speeddemon

///Member
Bavs108 said:
It has a tinny/raspy sound after 3000rpm kind of like an M3 but she doesn't scream as loud:rollsmile: Below 3000rpm there is a bit of a rasp but it sounds more or less like it did before. I will try to take a video later although I may need some help uploading it:flyfun:

To be honest my intention with this mod was more for the sound. I was not expecting such a big improvement performance wise. I think the biggest restriction in the system are those manifold cats. I did quite a bit of research before going ahead with this and read of people getting little to no improvements in performance, but I think that's due to people removing just the mid cats, because they're the easiest to remove, then expecting big improvements and end up disappointed.

I did the exact same thing with my ex 330i....and it was nice but then i removed the standard backbox and replaced it with a Van der Graaff one and it was amazing for the sound and def much better throttle responds:thumbs:

My opinion from experience is to go van der Graaff backbox and u wont look back:thumbs:
 

moranor@axis

///Member
Official Advertiser
YUBEN said:
The strange thing is that a supposedly reputable company like Van Der Linde did the exactly same thing on the mainfold cats like Bavs car on Sankukuers 330.

it is the easy way to make sure pipes are not miss aligned this is the only possible reason why they would do it this way...
ask any engineer if this void would be good for flow and he will tell you no...

reason why the diameter is so big around the cat is to compensate for the volume taken up by the cat with it removed it is too big...
 

Henry330i

Active member
I've done the same to my 330i the cats in the headers were cut out and straight pipes welded in. Happy with the sound. Oh ever it does sound very tinny on cold starts. But goes away after a couple of seconds.

Sent from my GT-I9300 using Tapatalk
 

Bavs108

///Member
moranor@axis said:
hollowing out the cat cases is not good in terms of flow dynamics...

the massive increase in pipe diameter kills the exhaust gas velocity this is bad for performance... you will get more out of this if you fitted pipe the same size as the rest of the system...

anyone else considering this should cut the pipe before and after the cats and use pipe to join :)

a resonator can be used to kill rasp in place of the secondary cats

Yes I actually discussed this with Yuben and GT. I figured I would see how it performs like this and if I'm not happy with it we can always replace it with a resonator or straight pipes later. I'm actually quite happy with it performance wise:rollsmile: The only thing that I think might get to me is the raspy sound in the cabin. I will see how she runs over the next few weeks and look into resonator options to reduce the rasp:thumbs:

moranor@axis said:
YUBEN said:
The strange thing is that a supposedly reputable company like Van Der Linde did the exactly same thing on the mainfold cats like Bavs car on Sankukuers 330.

it is the easy way to make sure pipes are not miss aligned this is the only possible reason why they would do it this way...
ask any engineer if this void would be good for flow and he will tell you no...

reason why the diameter is so big around the cat is to compensate for the volume taken up by the cat with it removed it is too big...

This is exactly why we did it like this. So that the alignment is perfect. We also checked if 328 or M3 manifolds would fit on my head, but my head for some reason does not have the extra holes to accommodate those. We would have to drill and tap into the head to get the studs aligned. I think only the pre 2003 heads came with extra holes.
 

moranor@axis

///Member
Official Advertiser
you dont have to use all the holes on the headers if you dont want to drill and tap :)

on my pref/l e46 the holes were there but were not tapped i had them tapped when I fitted the Viper branch
 

Bavs108

///Member
Please excuse the dirty exhaust tips:flyfun: Here's a before and after video:rollsmile: Let me know if it works:idea:

[video=youtube]
 

GPGrobler

///Member
Hi,

I have seen quite a few posts about de-catting, is there anyone who de-catted a 2002 E46? Will the 2002 need cat foolers? Does removing the cats worsen fuel consumption? Will the car need to be chip tuned after removing the cats? How much performance do cats rob the car of? I have heard that up to 10kw is lost due to catalytic convertors, is this true?

Thank you in advance.
 

Kish2604

Administrator
Staff member
Bavs, tbh the process you used is not exactly my cuppa tea esp when considering the m54 and the way it sounds out the factory, my ex 330i went to a work colleague and I see it everyday... I promise you hearing that car starting up in a underground parking lot will make many hairs stand on edge,

I chose to use the 328 catless manifolds as swop outs over the stock manifolds and replace the centre cat with a resonator. The car had a deep idle, punchy tone mid rpm and at the top you could hear the engine wail..

Diff strokes I guess...
 

moranor@axis

///Member
Official Advertiser
GPGrobler said:
Hi,

I have seen quite a few posts about de-catting, is there anyone who de-catted a 2002 E46? Will the 2002 need cat foolers? Does removing the cats worsen fuel consumption? Will the car need to be chip tuned after removing the cats? How much performance do cats rob the car of? I have heard that up to 10kw is lost due to catalytic convertors, is this true?

Thank you in advance.

I have not seen an e46 that needs cat foolers yet dont think we got post cat sensors in SA

fuel consumption and power get better with Decat :)
 
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