Is there a perfomance advantage to not having secondary cats.

craigmc163 · 07-30-2011, 02:09 PM

I was hoping Someone could help me out. I have a 06 330xi and have GT haus exhaust on it (fake eisenmann) it is sections 2 and 3 and the race version! The muffler shop that put it on for me told me that I did not need the back cats? What I am wondering is, do I? Not sure if they were there help create back pressure and sound reduction? Should I keep the track pipe on the car or put the secondary cats back in.
The cars sounds amazing the way it is! Sorry if this is a dumb question! I know there is a lot of info in these threads but I can\'t seem to find anything on this.

kamek · 07-30-2011, 02:13 PM

I'm not sure if there are any gains or losses from removing the secondary cats, but I haven't *felt* a difference with mine gone. It does make the car louder with them gone, though.

Dark_Knight_335 · 07-30-2011, 02:51 PM

Maybe a weight saving advantage. Beyond that, I can't imagine any performance gains or losses, only sound changes.

Dr. Nate · 07-30-2011, 05:53 PM

Quote:

Originally Posted by SDeFranco1

Maybe a weight saving advantage. Beyond that, I can't imagine any performance gains or losses, only sound changes.

I agree, back pressure is a very tricky beast and todays modern cats aren't nearly as restrictive as they use to be. Without someone posting up dyno and 1/4 mile times for before/after it is hard to say definitively whether or not you'd see an increase or even a decrease in power.

-Nate

07-30-2011, 02:09 PM	#1
craigmc163 fulltilte90 11 Rep 199 Posts Drives: 06 330xi Join Date: Dec 2010 Location: Nashville tn iTrader: (7)	Is there a perfomance advantage to not having secondary cats. I was hoping Someone could help me out. I have a 06 330xi and have GT haus exhaust on it (fake eisenmann) it is sections 2 and 3 and the race version! The muffler shop that put it on for me told me that I did not need the back cats? What I am wondering is, do I? Not sure if they were there help create back pressure and sound reduction? Should I keep the track pipe on the car or put the secondary cats back in. The cars sounds amazing the way it is! Sorry if this is a dumb question! I know there is a lot of info in these threads but I can\'t seem to find anything on this. __________________ Bilstein Sports, H&R Lowering Spring, Blacklines, Custom Alcantara Shift boot and Brake Boot, BMW performance shift knob, BMS Power Box, DAEOS Harness, BMS Angel eye upgrades, Injen Performance intake, GT haus Full exhaust system.
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07-30-2011, 02:13 PM	#2
kamek Brigadier General 366 Rep 3,447 Posts Drives: 2018 X3 M40i Join Date: Mar 2008 Location: Queens, NY iTrader: (4) Garage List 2008 BMW 328xi [8.20]	I'm not sure if there are any gains or losses from removing the secondary cats, but I haven't felt a difference with mine gone. It does make the car louder with them gone, though.
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07-30-2011, 02:51 PM	#3
Dark_Knight_335 Came to the N55 Darkside 1139 Rep 12,740 Posts Drives: 2011 335 E93 M-Sport Join Date: May 2010 Location: NY/NJ iTrader: (28)	Maybe a weight saving advantage. Beyond that, I can't imagine any performance gains or losses, only sound changes.
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