Has anyone knocked out everything inside their cat for better airflow. If so how does it affect the sound? Thanks

 

I have a gutted cat on my 86 camaro with a 2.8 and it really helps the sound. My buddy has a 350 in his 86 with a flomaster exhaust and it sounds the exact same as mine and I think mine flows A LOT better but the cat still gets hot as hell. BUT emissions will fail you real quick but since it is still on the car it does not scream like a exhaust without a catt.
David

 

mines gutted, sound got louder but more hollow. for some reason i gained TONS of low end torque

 

might gain power might not
problem when you put a gutted cat inside your exhaust is the big open then closing of your pipe system can create turbulence which will slow the exhaust gas down.
best way to do it and also the best sounding way if you ask me is to either put a straight pipe in there or a pre-silencer which is kinda just a straight through muffler with a perforated core rather then a louvered core

 

Ya know I fvckin love it! At first I was thinking, wait a minute wouldn't gutting the cat make the exhaust system much freer flowing. And since Brody stated that he gained TONS of torque, I was like oh man! Maybe Rx7Speed is right, freer flowing exhaust system makes more torque.... HAHAHA nope. Below you will see where he just proved himself wrong!

He just proved my statement correct, that with more backpressure by slowing down exhaust gases (or as he calls it, turbulence) will create more torque.
...Ya see Rx7Speed said that gutting it would actually cause turbulence making backpressure. And since Brody said he gained TONS of torque, that means they are hand-in-hand, backpressure will create more torque! Thanks Rx7Speed, for proving yourself wrong, and proving me correct. Now ya can shut yo mouth.

 

sorry guys about chevyluva3
there has been a little bit of a debate going on at https://www.thirdgen.org/techbb2/sho...&postid=478574

and what I said still holds true though
backpressure is bad
turbulence can cause backpressure which is bad
now how brody could have gained lots of torque is if his cat was plugged which would cause even more backpressure then what a guttedone would cause

 

hahaha, gosh your stubborn, he said nothing about back pressure, he said turbulence in the exhaust flow, there is a big difference. say you have a nice smooth exhaust flow and about half way down your pipe there are a few sharp bumps or some kind of a weird angled plate inside, your exhaust flow gets jacked up when it passes that point of the exhaust system, he said maybe or maybe not depending on how far the exhaust has to travel in the first place

 

on my car I had the stock exhaust setup with three cats myself
I had one of them plugged up quite bad so when I gutted the first two I gained a little bit of power not much but a little
but when I put a straight pipe in instead of the gutted cats as well as replace the main cat I gained a LOt of torque through my whole rpm range
when I put the straight pipe in I reduced a lot of backpressure

if you can do it go with a straight pipe
not goin to pass smog with it so again only if you can get away with it
or have it setup so you can swap when smog time comes

 

Umm, turbulence is also considered backpressure. You just said if there was a few bumps in the way, the exhaust would get "jacked" up, yeah well a few bumps in the way will slow down the exhaust, creating back pressure.
I'd hate to do it but I'm going to make an analogy, if you were going down the highway and out of no where there was speed bumps there. You would either slow down, or hit the bump and go flying. Either way if you crash or slowdown, the cars behind you, and the cars behind them, and behind them, will have to slow down. Causing it to be "backed" up (back pressure) or as you call it jacked up. But lets not bring the discussion over here. Brody proved my point over here.

 

chevyluva
you there are other things like a cat that has been plugged up that could cause him to gain power when the cat was gutted
and if anyone has a clogged cat and you dont have the money for a straight pipe go for it and gut it
and also you gut the cut you are still freeing up the exhuast to an extent
that is why it is kinda iffy though
some cats are not that bad on creating backpressure (high flow cats) and are made to flow with as little amount of backpressure as you can get with one of those things. now you get them chances are you are going to lose power
though if you take a plugged up cat that is creating massive amounts of backpressure then gutting it is going to help a lot

all depends on the shape of the cat

now if you want to talk backpressure keep it on the other thread please

if you talk here please keep it about the cat and if it is good or not and why

 

All CATs act like mufflers. By removing the filling you're also going to increase the loudness of your exhaust system. In some cases you may screw up the tuning and get resonance at cruise speed which will drive you nuts.

Have the proper CAT is far better than having a gutted CAT. A gutted CAT causes a sharp increase in pipe size that hurts flow. Actually, it does it twice because of of the inlet and outlet. A well made CAT is far better. The honeycomb actually contributes to good air flow because it straightens the path of air and significantly reduces turbulence. But the best performance would come from a straight pipe. By the way. There's no such thing as backpressure. Stop using the term.

Random Technologies makes a great CAT.

 

ChevyLuva...

Reference the the thread link above. I explained the issues for you in that thread.

 

Thanks everyone who responded. I wll either say hell with it and GUT it or buy a Random Technologies Cat like QWKTRIP said.

 

well, i gutted my cat last early summer. it does sound more hollow, but man, i did notice a little kick in the pants with more get up and go. im putting on headers this early spring, so to get rid of the "hollow" sound, im just going to weld in a straight 3 inch inside of the cat, to kill that hollow-tinny noise. between that then, the headers, and flowmaster, i think it should flow and sound very pleasing. and also, then i can pass a visual inspection every year.

 

I should clarify that the stock CAT is so terrible that gutting it is probably is a power increase even though it's not the preferred solution.

 

I'm getting the idea that everything STOCK is CR@P. What the hell does our cars have that is stock and good?

 

its just if you want a "serious" performance musclecar, you have to go through and replace a lot of parts with performance parts. just be thankful that the camaro has a lot more going for it out of the factory than say, a honda?

 

you are lucky you dont have three of the bastards

 

actaully he did say something about backpressure with out stating it, rx7 said that the big opening slows the gas down because of turbulance which is correct, this is less backpressure, and that will creat turbulance, which can make you loose power your best be would be to get an off road pipe, once agian i gotta back up my chevy man

 

just to add to rx7's you are lucky you dont have three, my trans am has 4, keep dreamin'

 

The power steering and Bilstien shocks if you have those. And if you have 1LE brakes you're doing well.

Our cars flex and need frame reinforcement, the rears blow up, every piece of the suspension is inadequate, the engines have cast pistons, TPI runners are waaaaaaay too long, the single exhaust sucks, the radiator is taxed at stock power levels, it has McPherson strut suspension, and the doors are so heavy they have to be realigned every now and then. Did I mention most the original paint jobs cracked and peeled? Our cars suck. But they're fun and Mustang is just too ugly for me. Oh, did I mention the stock Ford ECM can handle an 11 second car?

 

I had to put a cat in my car (88 IROC L98) in October/November (forget exactly when). When I bought it, it had a gutted cat and would not pass an emissions test. So, I did some research, and settled on a Random Technologies Cat.

It only changed the sound a little, and I could swear that I have more torque now than before. By the way, the car had a Dynomax cat-back on it before and after.

To be technically correct, you have to realize that the computers are setup assuming a certain amount of backpressure. Once you change the backpressure too much, you will likely experience a step downwards in power...

 

There is nothing in the computer that keeps track of exhaust "backpressure." It does however have trouble metering the proper fuel when increasing air flow - and that's what you're doing.

 

4 of them?!?!?!


and I thought mazda messed up putting three inline

how did they have yours setup
parallel or inline?

 

There is nothing in the computer that keeps track of exhaust "backpressure." It does however have trouble metering the proper fuel when increasing air flow - and that's what you're doing.

Yes, there is no sensor. However, there are many things in the computer that are done in the absence of a real sensor. Basic design parameters and basic physics are built-in to control loops. One is an ASSUMPTION of backpressure. That is all I am saying.

 

I think deleting the cat would be better than hollowing a stock piece. But I dont think you will gain that much hp., maybe 5-10.
Heres a story. One day I thought I would hollow out my cat.
Out comes the torch. Cut the cat off, and BAM, the F'r is already hollowed out. Damn, I think, all that for nothing. Well, turns out, not so bad. I get lazy, of course, and take the car to the muffler shop. I tell them to just weld in a 3 in. pipe in place of the cat. Done. Fast forward. Go to take the car home, and sure, the car has a smidge more torque, and sounds a little different. Huh I say. So, lesson learned, dont know myself. But I can say if you ever go to get your cat replaced, look to see if its hollow to start with, and legally permitting, tell them to put in a straight pipe instead of a stock cat. Turbulence BAD!
And a piece of pipe welded in only costs $20, for me anyways.