[Fredz]

Hi all,

Finally, I deleted the secondary cats of my xdrive car.

I bought this car and I had always find that the exhaust note of a 335i (n55) is louder than my 335xdrive (n55).

So I do some search and find on e90post forum that 335xdrive 2011 cars have secondary cats.

335i n55


I find this thread : http://www.m3post.com/forums/showthread.php?t=457202

...And I did like this.



I only cut the exhaust and remove the catalyst material and reinstall the exhaust.

my car


The result is good. The sound is a little more sportier and louder .... like a 335i 2011 with no secondary cat.

I don't know if I had an hp gain, but I have not find that I lose anything after one day of driving....

Took me about 2 hours for uninstall and reinstall and 30$ at a shop for welding.

[elinstylez]

Looks good!

[kavadarci]

if you removed the cat's material why didn't they just weld straight pipe?
and where is your resonator, i have resonator in the middle where the x section of yours is.

[bulldog_yyc]

i have a set of OEM midpipes (with cats, off an E90 335i) for sale in Toronto if anyone wants them for a project - hit me up via PM

[Fredz]

Originally Posted by kavadarci

if you removed the cat's material why didn't they just weld straight pipe?
and where is your resonator, i have resonator in the middle where the x section of yours is.

I only remove the mat's material because I want to keep an OEM look.

The cats are also the resonator.

What you see is an OEM exhaust sytem of 335 xdrive N55 2011.

[obert]

I like the idea but now if you need stock cats back on for some reason you will have to buy them. If you would of put strait pipe and kept the cats you would not have to buy new one if you need them.

I am suprised the shop put them on with out the insides

[Fredz]

Originally Posted by obert

I like the idea but now if you need stock cats back on for some reason you will have to buy them. If you would of put strait pipe and kept the cats you would not have to buy new one if you need them.

I am suprised the shop put them on with out the insides

Hi,

Yeah, a lot of shop don't want to do that, but if they just do a welding; they don't ask question....

And only 335 xDrive (N55) have secondary cats, so I don't need them because N55 335i have no secondary cats.

[Malapropism]

Do you have a video?

[Fredz]

Originally Posted by Malapropism

Do you have a video?

No.

[335islover]

Originally Posted by Fredz

I only remove the mat's material because I want to keep an OEM look.

The cats are also the resonator.

What you see is an OEM exhaust sytem of 335 xdrive N55 2011.

still have cats.?

[335islover]

Originally Posted by Fredz

Hi,

Yeah, a lot of shop don't want to do that, but if they just do a welding; they don't ask question....

And only 335 xDrive (N55) have secondary cats, so I don't need them because N55 335i have no secondary cats.

I need your cats lemme know

[trohde78]

Does anyone know why the xdrive would have extra cats if the non-xdrive does not? Seems like an unnecessary cost for BMW if they aren't needed for emissions.

[jwzimm]

Originally Posted by trohde78

Does anyone know why the xdrive would have extra cats if the non-xdrive does not? Seems like an unnecessary cost for BMW if they aren't needed for emissions.

When BMW went to the N55 in the 335i they went with a larger, dual core primary cat in the downpipe. There is speculation that the primary cat had to be smaller on an x-drive due to the x-drive hardware in the area. In order to meet emissions they left the secondary cats in place on the x-drive N55's.

[trohde78]

Originally Posted by jwzimm

When BMW went to the N55 in the 335i they went with a larger, dual core primary cat in the downpipe. There is speculation that the primary cat had to be smaller on an x-drive due to the x-drive hardware in the area. In order to meet emissions they left the secondary cats in place on the x-drive N55's.

OK, I'll buy that reasoning.

[jwzimm]

Originally Posted by trohde78

OK, I'll buy that reasoning.

It makes sense but I have not confirmed it. I have checked on realoem.com and the downpipes are different part numbers between the x-drive and regular 335i so that lends credence to the theory.

It has been speculated that a regular 335i could install an x-drive downpipe and take advantage of the (potentially) less restrictive primary cat in the x-drive downpipe.