E90 335i Cat removal options

[NZLSAF 0]

Hi all,

Convinced my old man to get into an E90 335i M-Sport and have now talked him into playing with it a bit, he is looking into removing either the primary or secondary cat and as such we are looking for some advice.

1st has anyone perfomed the same mod, i've done a little reading, mechanically its pretty straight forward

2nd what issues are encountered with the exhaust sensors once they're removed

3rd so that he can keep it above board are there any suggestions for places he can take it to have the work done in a clean and tidy manner.

Ideally an off the shelf system would be great but he wants to keep it stockish

thanks for the feedback

[jake1829 119]

Hi Chad,

Primary cat = getting downpipes (if you have mechanical warranty, may want to check conditions as the autosure warranty is voided with that removed) - you will also need to code out the cat check otherwise the orange engine light will pop up on your dash

2nd cat was removed as I had a aftermarket exhaust system installed - I think Josh had his stock exhaust modified with the secondary cat removed (will ask him)

All my modifications and work done to my 335i has been done by Bmworkshop Botany

EDIT****

Josh has his e90 335i stock exhaust modified to remove the 2nd cat by Takapuna mufflers - but wasn't that happy with the work

"Wouldn't recommend them, they didn't didn't take the exhaust off and left holes in it"

Edited December 4, 2014 by mod335

[Stevie S 49]

Hi all,

Convinced my old man to get into an E90 335i M-Sport and have now talked him into playing with it a bit, he is looking into removing either the primary or secondary cat and as such we are looking for some advice.

1st has anyone perfomed the same mod, i've done a little reading, mechanically its pretty straight forward

2nd what issues are encountered with the exhaust sensors once they're removed

3rd so that he can keep it above board are there any suggestions for places he can take it to have the work done in a clean and tidy manner.

Ideally an off the shelf system would be great but he wants to keep it stockish

thanks for the feedback

If he wants to keep it stockish probably not much point, there won't be any performance gain. Little to gain from removing secondary cats, to get any benefit from removing the primary's you will need an aftermarket tune to run. Its very tight in there so wouldn't recommend anything other than aftermarket downpipes.

I like many other 335 owners on here will warn you. Once you pop you can't stop,

[NZLSAF 0]

Has anyone removed their secondary Cat's and had issues with warning lights?

Also, whilst he's at it I'm thinking a cold air kit wouldn't hurt either, has anyone used the "aFe Stage 2 Pro 5R" kits before, they look like quite high quality bits of kit.

http://www.ebay.com/itm/2007-2010-BMW-1-3-5-Series-E90-E92-aFe-Stage-2-Pro-5R-Cold-Air-Intake-System-CAI-/271217684722?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f25d570f2&vxp=mtr

[Bigmor 4]

Watch this....most standard air boxes are better designed that after market ones. You might get a different sound at best.

[HaNs 226]

You can remove 2nd cats with no issues. The Milltek exhaust for them removes them.

Not sure how R34 intake tests are relative to N54 335i intakes?

[jake1829 119]

Plenty of data around the US forums about how the standard intake is restrictive once power is dialed up , I just run the BMS intakes - love the sound under WOT - would love to get the Dinan CF intake, but can't justify spending over 1K US for 10HP gain, just spent 100US for the same thing!

Edited December 11, 2014 by mod335

[Stevie S 49]

I also run the bms intake. General consensus its the best bang for buck intake, and the afe offers no advantage.