Removing the Cats


MNJason

GT Owner
May 14, 2010
2,096
San Diego
I have an 05 with tune/pulley. Stock headers. H pipe exhaust. I'd like to remove the CATS to make the car louder and also hoping to get some more "pop and gurgle" out of her. Thoughts on this? Anyone have a similar setup? Thanks!
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
I run mine without cats all of the time - virtually the same set-up as you. Yes, louder and more "personality".
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,256
i didn't run cats for a while but it was way too loud i put race cats back on its still too loud, I have stainless exhaust
 

twobjshelbys

GT Owner
Jul 26, 2010
6,053
Las Vegas, NV
I presume you don't have emissions testing there. You will need a tune that disables the rear O2 sensors or you'll have a persistent check engine light.
 

spartan

GT Owner
Mark II Lifetime
Feb 11, 2017
1,216
Bloomfield Hills MI
I went back and forth deciding to remove the OEM cats. Decided to leave them so I cant comment. With the cats on its not very loud so if you want loud take them off.
 

MNJason

GT Owner
May 14, 2010
2,096
San Diego
Im comparing mine to two local cars with the Ford Racing Headers and Borla exhaust which I think sounds perfect. I would say most people think its too loud. Not for me.

Yes, no emissions here. I have a pulley and tune so I assume disabling those sensors is not a big deal?

Thanks for all the comments and help!
 

twobjshelbys

GT Owner
Jul 26, 2010
6,053
Las Vegas, NV
Im comparing mine to two local cars with the Ford Racing Headers and Borla exhaust which I think sounds perfect. I would say most people think its too loud. Not for me.

Yes, no emissions here. I have a pulley and tune so I assume disabling those sensors is not a big deal?

Thanks for all the comments and help!
If you have a sct tuner or equivalent your tuner should be able to send one you can load. Doing so resets all system readiness and pending codes. Your tuner box might be able to read the status but I'd recommend getting a obdii Bluetooth reader and just keep it plugged in.
 

MNJason

GT Owner
May 14, 2010
2,096
San Diego
So do they make test pipes for this car? Or do I need to have them made?
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
Ford Racing used to make Cat delete pipes. Just maybe you can find someone who is not using them...
 

33Bravo

GT Owner
Mark II Lifetime
Nov 3, 2006
688
Minneapolis, MN
Long tube headers Jason!
 
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MNJason

GT Owner
May 14, 2010
2,096
San Diego
Do you think H pipe plus no cats is much louder than headers and Ford racing exhaust? The tuner I am talking to says yes. MUCH yes.
 

Sinovac

GT Owner
Mark II Lifetime
Jul 18, 2006
5,832
Largo, Florida
 

Xcentric

GT Owner
Mark II Lifetime
Jul 9, 2012
5,213
Myakka City, Florida
 

NorthwoodGT

GT Owner
Jun 12, 2009
1,215
Michigan
there are also some after market companies making a test pipe with mini cats that include the bungs for the O2 sensors. they've been on fleabay in the past. the Borlas look interesting. wonder how they sound compared to the OEM?
 

Bill Briley

GT Owner
Aug 9, 2005
212
Valley Forge PA.
SS Ford Racing Headers (No Cats) and stock muffler .......The sound is intoxicating !!
Pull into a Cars and Coffee and watch the crowd gravitate toward the GT Symphony .
 

Sinovac

GT Owner
Mark II Lifetime
Jul 18, 2006
5,832
Largo, Florida
there are also some after market companies making a test pipe with mini cats that include the bungs for the O2 sensors. they've been on fleabay in the past. the Borlas look interesting. wonder how they sound compared to the OEM?

I've never seen or heard them on a car.
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,256
SS Ford Racing Headers (No Cats) and stock muffler .......The sound is intoxicating !!
Pull into a Cars and Coffee and watch the crowd gravitate toward the GT Symphony .


I have never seen or heard of this set up, usually the first that goes in an exhaust install is the factory muffler. do you have any vids?
 
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nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,176
Do you think H pipe plus no cats is much louder than headers and Ford racing exhaust? The tuner I am talking to says yes. MUCH yes.

This is essentially a question of comparing a system with a muffler and one with absolutely no muffler. No muffler is quite a bit louder. Note that on your current set-up ==> cats + h-pipe, the cats do a fairly reasonable job of acting as a pseudo muffler. Replace those with bypass pipes and you essentially have no muffler action at all.
 

Xcentric

GT Owner
Mark II Lifetime
Jul 9, 2012
5,213
Myakka City, Florida
Do you think H pipe plus no cats is much louder than headers and Ford racing exhaust? The tuner I am talking to says yes. MUCH yes.

By "Ford racing exhaust," do you mean the Borla/FRPP muffler?

If yes, then I think no cats + H-pipe will be louder. The Borla/FRPP muffler with long tube headers mutes the noise at idle, light throttle, steady throttle. However, open the throttle and it is LOUD. It sounds like there is no muffler. Like you might expect a valved muffler to sound. I think the Borla/FRPP muffler takes out some of the rasp of a rear exit header system and adds a bit of baritone/bass.

No cats + H-pipe would not have anything to quiet the exhaust except for the minor effect of the cast iron manifolds. I have not heard this particular setup, but that is why I think it would be louder.

The Borla pipes are pricey. Why not just gut the cats? If you want to be able to return to stock someday, I'm sure there are tons of cat pipes in forum members garages. I'll sell you mine for less than the cost of the Borla pipes. ;)
 
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NorthwoodGT

GT Owner
Jun 12, 2009
1,215
Michigan
small cat by magnaflow.jpgI found the small cats. they are 3" in x 3" out and a total of 9" long made by Magnaflow. somebody was making a test pipe for the GT with these cats already installed and a bung in the pipe for the O2 sensor.