Removing catalytic converters?

E90 Saffa · 09-26-2024, 12:17 PM

Good day.

Do mini “cats/cat foolers” actually work? I’ve had the cats removed, but sometimes when I use cruise control on the highway my engine light will come on, with the codes
-“Catalyst System Efficiency Below Threshold Bank 1”
-“Catalyst System Efficiency Below Threshold Bank 2”

This does not occur frequently, always on highways.
It also only happens under load, eg. on cruise control with speeds above 100km/h or on steep uphills where I have to put my foot down in order to maintain speed.

Just the fourth time it has happened since the cats are out. The car doesn’t go into limp mode and I don’t notice anything different, just the half engine light that comes on. The only thing I’ve noticed is that my car is a bit heavier on fuel.

whyzee125 · 09-26-2024, 12:32 PM

Are you not running a tune?

There's really no benefit to removing cats if you aren't running a tune that takes the downpipes/cat delete into account.

You should get MHD and run a tune designed for no cats--the car will be more efficient, boost more, and keep your CEL off.

EDIT: Nevermind just saw you're not n54/n55. A tune is still probably your best bet but your options are different than the turbo 6s.

09-26-2024, 12:17 PM	#1
E90 Saffa New Member 2 Rep 9 Posts Drives: 2007 E90 320i Join Date: May 2023 Location: South Africa iTrader: (0)	Removing catalytic converters? Good day. Do mini “cats/cat foolers” actually work? I’ve had the cats removed, but sometimes when I use cruise control on the highway my engine light will come on, with the codes -“Catalyst System Efficiency Below Threshold Bank 1” -“Catalyst System Efficiency Below Threshold Bank 2” This does not occur frequently, always on highways. It also only happens under load, eg. on cruise control with speeds above 100km/h or on steep uphills where I have to put my foot down in order to maintain speed. Just the fourth time it has happened since the cats are out. The car doesn’t go into limp mode and I don’t notice anything different, just the half engine light that comes on. The only thing I’ve noticed is that my car is a bit heavier on fuel.
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09-26-2024, 12:32 PM	#2
whyzee125 Brigadier General 2003 Rep 4,030 Posts Drives: Dinan stage 2 335i Join Date: Jul 2014 Location: Chattanooga Tn iTrader: (0)	Are you not running a tune? There's really no benefit to removing cats if you aren't running a tune that takes the downpipes/cat delete into account. You should get MHD and run a tune designed for no cats--the car will be more efficient, boost more, and keep your CEL off. EDIT: Nevermind just saw you're not n54/n55. A tune is still probably your best bet but your options are different than the turbo 6s.
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