Removing secondary cats

pysical

Sergeant
Jun 16, 2017
348
75
0
Ride
2009 335xi E90
Is this a simple job for a basic exhaust shop? I am looking to get them removed and figured a exhaust shop should be able to do it? If not, is there a similar priced option for getting them removed? Was thinking about new exhaust that goes back to rear axle as I want to keep my mufflers.
 

_mhs

New Member
May 25, 2018
1
0
0
Should be simple job for an exhaust shop.
Borla makes a set of catless midpipes as well.
(Edit: p/n 60503)
 

mnick

Private
Jan 11, 2018
26
7
0
Tampa
Ride
335is
Simple, 60mins and $80.
Drone was terrible so I ended up getting hi flow cats and had the same shop put them on 4 months later.

Clarification: I am running Catless down
pipes and Dynatech PowerCat Catalytic Converter, High-Flow, 3-Way, Stainless Steel, 2.5 in. Inlet, 2.5 in. Outlet, 11.5 in. Length.
 
Last edited:

InnovativeAuto

Specialist
Mar 14, 2018
77
21
0
Ride
Z4
Get ready for some stank! If it’s a DD I wouldn’t. And most exhaust shops are not going to remove all the cats (they can get a huge fine!). That might depend on where you live though.
 

pysical

Sergeant
Jun 16, 2017
348
75
0
Ride
2009 335xi E90
Simple, 60mins and $80.
Drone was terrible so I ended up getting hi flow cats and had the same shop put them on 4 months later.

Clarification: I am running Catless down
pipes and Dynatech PowerCat Catalytic Converter, High-Flow, 3-Way, Stainless Steel, 2.5 in. Inlet, 2.5 in. Outlet, 11.5 in. Length.

Did your car change in sound much when you got rid of the secondary cats?

And when you put the hi-flow cats on, did you lose sound and go back to normal? Or how was it?

I may do the hi-flow cats then.
 

mnick

Private
Jan 11, 2018
26
7
0
Tampa
Ride
335is
Did your car change in sound much when you got rid of the secondary cats?

And when you put the hi-flow cats on, did you lose sound and go back to normal? Or how was it?

I may do the hi-flow cats then.

I have the 335is, not sure if our exhaust is the entirely equal.

Also I have/had Catless dps throughout the following.

I removed secondary cats from mid pipe, and the sound and drone was terrible (“fart burner”, as my Wife says). However, turbo spool was improved.

Then placed hi flow cats on mid pipe (instead of the 1792 resonator) and sound and drone was near perfect. No perceived change in spool.

And then... I upgraded turbos, and it’s loud again, currently thinking about options...
 
Last edited:

Rob09msport

Major
Oct 28, 2017
1,928
662
0
Monroe CT
Ride
09 335i msport le mans 18 x5
I have the 335is, not sure if our exhaust is the entirely equal.

Also I have/had Catless dps throughout the following.

I removed secondary cats from mid pipe, and the sound and drone was terrible (“fart burner”, as my Wife says). However, turbo spool was improved.

Then placed hi flow cats on mid pipe (instead of the 1782 resonator) and sound and drone was near perfect. No perceived change in spool.

And then... I upgraded turbos, and it’s loud again, currently thinking about options...
New wife
Sorry couldnt help it
Seriously though have you tried seeing if could retrofit factory exhaust valve from non is exhaust
 
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