disemboweled cats....

ripped camel

ripped camel

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So my cats were disemboweled and the beast feels MUCH quicker! It's definitely much peppier and it has nothing to do with the sound making it seem quicker because it didn't get much louder.

For those interested in the sound level increase, It sounds just a tad bit louder than before but still nothing much. It's still quieter than my 03 GT was when it had just a Borla catback. My setup now is gutted cats, magnaflow dual in dual out X muffler in place of 3rd cat, and magnaflow dual exhaust. Although I wish it to be just a little bit louder, there comes a point where you just be happy with what you have and call it a day.

I did throw three CEL's but am having them fixed via my SCT handheld tuner. I'll update this thread if a tune completely eliminates the CEL's or not.

I just figured since I didn't see many posts in my search about this I would post my experience for future users.
 
Turn off the rear O2 sensors in the tune. That will stop the CEL. I cann't say that it made mine any faster. Thats track proven.
 
I'd bet its new found speed is mostly in your mind, unless you had a plugged up cat beforehand.
 
How do you figure? Increased airflow going out creates more power. A cat is not a straight through flow so when it is hollowed out it is the difference between trying to breathe through a cotton ball or taking the cotton ball out of your mouth.

Have you ever seen a dyno before and after on a 2v motor with just adding an ORH or ORX? You always pick up atleast 7-12hp depending on your other mods. With that being said a 4v which has better breathing heads would benefit more greatly from a free flow exhaust system.

Are you saying deleting the cats is not a mod that increases performance?
 
I'm saying that I didn't see any improvement at the track after I gutted them. Thats what counts right actual improvment. Are you running stock manifolds? Have you seen how tight they are before the cats. Have you noticed how big the cats are.
 
htrdlincoln98 said:
I'm saying that I didn't see any improvement at the track after I gutted them. Thats what counts right actual improvment. Are you running stock manifolds? Have you seen how tight they are before the cats. Have you noticed how big the cats are.
Click to expand...

I was talking to MediumD.

Yes the cats are big. Have you seen the inside of them? You realize it's like a giant honeycomb wall. So eliminating that wall would allow better airflow.

Look at it in another perspective...people get headers to get better more efficient airflow. So wouldn't you think removing something that blocks airflow would net good gains?

Any car I've added mods too made a great improvement from eliminating the cats. Out of all the mods I've done to this car, eliminating the cats made the car feel much faster than every other mod I've done yet.
 
cats make a huge difference in some cars. i cut the one out in my 93 cutlass and it was like a whole other car. havent tampered with the marks cats yet
 
I have to say that when I removed the cats(4)from my 5.0 and put on a h-pipe,I know my fox is faster then it was before cause now I'm faster then my friends 2009 stang and he always beat me before by a couple cars at least
 
Yes I've seen the inside of the cats. I gutted mine some time ago Thats how I know it didn't make any real difference. The stock manifolds on the marks are pretty small right before the cats. On other cars it might make more of a performance difference due to the stock manifolds or headers. I think the 5.0 mustangs came with factory headers. Not great headers but much better than the mark manifolds. I pulled off both exhaust manifolds yesterday, I cann't believe how restrictive they look....
 
removing the cats does increase flow due to removing the restriction.


gutting and leaving a empty hollow shell does not improve flow and in many cases creates an expansion chamber that allows gasses to expand and cool which is bad.

and i agree 99.99999999999999% the butt dyno lies.
mine has lied to me several times
 
i dont guess you have a baseline et to base any real gains that might have been gotten either...
 
XLRVIII said:
i dont guess you have a baseline et to base any real gains that might have been gotten either...
Click to expand...

Sure I do in my sig. The dyno done in my sig is with all the mods listed minus the cats being gutted. I'll go get another dyno done to see what I picked up. I just need to wait for my tune to be re-emailed to eliminate the double lean codes I'm getting.

I do agree XLR that hollowed out does create a form of turbulence because it's not a straight through design as it would have been if they put a straight pipe in it's place like they were supposed to do. I told them that's what I wanted and they told me it was too hard to do with how the cats were connected to the headers.

This mod definitely feels faster than any of the mods I've done yet.

But I definitely agree that a straight pipe would have made a much better and efficient flow than just hollowing out the cats. I'm still pissed that guy did that...but what am I going to do.
 
It would be a major job to weld a pipe in place of the cats. IMO If your paying some one to do that then have them put headers on. Most likly the manifolds would have to come off the motor. If not it would be but a few extra minutes to remove the 16 bolts. The real restriction is in the exhaust manifolds right before the cats.....
 
when I did it to my svo mustang

i picked up about 3HP peak but lost alot everywhere else, keep in mind peak numbers aren't the whole story
 
Also remember that dyno numbers from one dyno on a given day and another dyno on another day could vary more than modded your cats... track times... track times...
 
XLRVIII said:
gutting and leaving a empty hollow shell does not improve flow and in many cases creates an expansion chamber that allows gasses to expand and cool which is bad.
Click to expand...

This is what I was getting at.


The honeycomb structure of modern cats isn't THAT bad anyway unless it gets full of crap... you should see the bead style cats from the 70s and early 80s..
 
WOW! I'm amazed, this is about the most intelligent conversation I have seen in a long time.






Jeff
 
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