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Secondary Cat Removal - HP and Noise Gains

24K views 15 replies 8 participants last post by  NobleM400 
#1 ·
I've searched a while, but haven't been able to come up with much good data on the horsepower and noise gains with just secondary cat removal. According to some very knowledgeable people, there is 8-10 hp to be gained from the removal. A big advantage is you don't have to worry about the oxygen sensor, and it's easily reversable.

From what I've seen on the search, there is not a significant increase in the noise, but there is some. Does anyone have input on how much performance increase you would see just from the secondary cat removal alone?
 
#2 ·
I assume you already saw this thread http://www.m5board.com/vbulletin/showthread.php?t=88730

So, minimal gain with just section1&2, I believe most of air restriction is on the OEM header/precat.

From noise level, IMO, justsection1&2 alone sound so stock with a little raspy at the higher rpm, but magnitude will increase dramatically with aftermarket muffler.
 
#3 ·
I assume you already saw this thread http://www.m5board.com/vbulletin/showthread.php?t=88730

So, minimal gain with just section1&2, I believe most of air restriction is on the OEM header/precat.

From noise level, IMO, justsection1&2 alone sound so stock with a little raspy at the higher rpm, but magnitude will increase dramatically with aftermarket muffler.
Thanks - I hadn't caught that one. Looks like without the dip at 7500 rpm the gain would have been in the 5-10 hp range. Nice torque gains as well. For the minimal price, I'm seriously considering that mod.
 
#4 ·
If you are interested in replacing your exhaust set up with some aftermarket stuff, let me know.

I carry SS and many other brands as well, like RDsport, eisenmann, etc.

It all comes down to preference.

Let me know if you have any questions.

-Don
 
#5 ·
mike,

is the 2nd cats you are speaking of replaced with the x-pipe?
 
#6 ·
as a matter of fact just yesterday i spent 4 hrs removing my ss race and x pipe and installing eis sec 1 sec cat delete eis sec 2 eis x pipe and eis sec 3 sport mufflers !!

so my initiial impressions were that even with all 3 the system is still fairly quiet like 40% louder than stock not even close to eis race by itself !! inside the cabin there's defenetly more v10 noise esp under the front seats , i like it !! and finally i really didnt notice any negligable power changes although it did feel like it was flowing alot better like he power was smoother or something !!
 
#11 ·
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