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will i loose power with a hollowed out cat

This is my baisic understand. You should find slight (Very small) gains by removing your cc, but you do need backpreasure which your mufflers and general piping will supply. Now straight pipe that is a different story. With straight pipe you can lose hp and If I remember right burn/blow out the tops of you pistons. It has been along time since my formal automotive training and it is very late but I do believe this should answer your question.

P.S. An old school "Getto" method to do the exact thing your talking about is to smack it with a hammer which breaks the combs out. then unbolt it right after cc and blow all the combs out creating a hollow cc, But I dont reccomend doing that. It' the Mickey Mouse verson.:laugh:
 
Oh, jeez; you people and your "backpressure"... that was one of the most off-base posts I've seen in a long time...

Hollowing out the catalytic converter might hurt performance because of the big empty chamber in the exhaust, which then crams back down into a pipe. It causes TURBULENCE, which slows down the exhaust, and it hurts the SCAVENGING effect that a good exhaust is supposed to have.

You're surely not going to burn any pistons. That's an old wives' tale.

Read up a little on your exhaust science.
 
backpressure?

:facepalm:

Exhaust should NOT create backpressure. A well designed exhaust creates no backpressure and exhaust pulses are able to move through it smoothly and at an even rate, thereby pulling the next exhaust pulse through. This effect is called scavenging, something that even any backyard mechanic worth his salt should be aware of.

To the OP. The best way to do this kinda thing is to cut off the pipe at the bottom of the cat, pull out the filling, stick another pipe inside your precats, then weld that pipe in, and weld the old pipe back onto the bottom of your cat. If you have a clogged precat, hollowing it out will give you some gain, if you have a good precat, I you will probably feel a loss. If you are really looking for a gain, put a set of headers on.

anyways, like andy bennet said and tex said

You wont burn/blow out pistons, it doesnt change compression.
 
FIND said:
backpressure?

:facepalm:

Exhaust should NOT create backpressure. A well designed exhaust creates no backpressure and exhaust pulses are able to move through it smoothly and at an even rate, thereby pulling the next exhaust pulse through. This effect is called scavenging, something that even any backyard mechanic worth his salt should be aware of.

To the OP. The best way to do this kinda thing is to cut off the pipe at the bottom of the cat, pull out the filling, stick another pipe inside your precats, then weld that pipe in, and weld the old pipe back onto the bottom of your cat. If you have a clogged precat, hollowing it out will give you some gain, if you have a good precat, I you will probably feel a loss. If you are really looking for a gain, put a set of headers on.

anyways, like andy bennet said and tex said

You wont burn/blow out pistons, it doesnt change compression.
Click to expand...
actually a very (and i emphasize very) small amount of back pressure is needed to keep from burning the valves. example: run an engine with straight headers and you have no problems, there is virtually 0 back pressure but its just enough (doesnt even have to be headers, even short individual pipes on each port is sufficient). run the same engine without anything off the ports, just open exhaust ports, and you will quickly burn the valves.

that said, the measurable amount of back pressure with just headers is essentially 0
 
so is it true that gutting it with good precats will cause a loss of HP? is this true if you upgrade to a high flow cat as well?
 
no, you shouldnt lose any HP. in fact gutting the precats will actually gain you a couple of HP. dont bother gutting the main cat, just replace it with a piece of straight pipe.
 
FIND said:
backpressure?

:facepalm:

Exhaust should NOT create backpressure. A well designed exhaust creates no backpressure and exhaust pulses are able to move through it smoothly and at an even rate, thereby pulling the next exhaust pulse through. This effect is called scavenging, something that even any backyard mechanic worth his salt should be aware of.

To the OP. The best way to do this kinda thing is to cut off the pipe at the bottom of the cat, pull out the filling, stick another pipe inside your precats, then weld that pipe in, and weld the old pipe back onto the bottom of your cat. If you have a clogged precat, hollowing it out will give you some gain, if you have a good precat, I you will probably feel a loss. If you are really looking for a gain, put a set of headers on.

anyways, like andy bennet said and tex said

You wont burn/blow out pistons, it doesnt change compression.
Click to expand...

see thats what i thought but i wasnt 100% sure. that website i posted with my thread has a website for a cc that already has the pipe going through it for like $35
 
striker2 said:
no, you shouldnt lose any HP. in fact gutting the precats will actually gain you a couple of HP. dont bother gutting the main cat, just replace it with a piece of straight pipe.
Click to expand...


except any visual inspection on the car's exhaust would get you in trouble. That's why the dummy CC the op posted might be a better solution.
 
I noticed a decent climb in top-end power when I gutted my precats. Of course, I've got headers now, so I realize how minimal that really was...
 
Andy Bennett said:
I noticed a decent climb in top-end power when I gutted my precats. Of course, I've got headers now, so I realize how minimal that really was...
Click to expand...

Other wise known as the mystery mod. (gutting your pre-cats)

It was a very common thing done on here (ceg). Most people used to praise doing this mod back when msds headers were $760..because nobody wanted to pay that amount. So most people gutted the pre-cats. It would be said that a 5-7whp gain was pretty accurate.
 
Well whatever. lol. I really like this forum but even though I have four years of technical college in auto mechanics and motorcycle mechanics. And have worked in the field for over 6 years, I seem to always be wrong to most of you.:shrug: I guess Its the whole being a newb on the website. It's just funny how when ever I write something. I alway get 2 to 3 answers telling me how stuipid I am to think what I think Then later on in the post my points are made by someone else and accepted?:shrug: I guess you all went to better 4 year auto schools than me.:laugh: ( that sound passive agressive doesn't it, sorry)

By the way I am not upset at all just a little disapointed I cant ever really help. As far as Burning out the tops of the pistons, Yes thats possible. You DO need some back preasure( A high flow muffler is a great way to acheive that), And pulling out your cat does help to increase power. Like I said the first Time, I stand behind what I said.

Also mabey this is just the dynamic of a forum. I have not been on alot of forums.
 
the problem is the loss on the bottom end, which IMO is worse than you experience with headers. Also, I think most of the gain from most people gutting precats would come from how easily the precats clog on these cars. This is the equivalent to changing spark plugs. I dont know, but I doubt anyone has ever done this on a newer or low milage contour.

Gutting the main cat wont make a smell, but your exhaust will sound like poopie. Plus there is no reason to do it. It is not a large restriction in your exhaust, and it makes the planet happy when you have it on your car.

striker2 said:
actually a very (and i emphasize very) small amount of back pressure is needed to keep from burning the valves. example: run an engine with straight headers and you have no problems, there is virtually 0 back pressure but its just enough (doesnt even have to be headers, even short individual pipes on each port is sufficient). run the same engine without anything off the ports, just open exhaust ports, and you will quickly burn the valves.

that said, the measurable amount of back pressure with just headers is essentially 0
Click to expand...

no, that just isnt true, it is close, and I am almost splitting hairs on this issue. I have put zoomies on engines, there is no problem, and that is just a straight piece of pipe that goes out of the ports anywhere from a few inches to a couple feet.

The problem with running open ports that causes you to burn valves is the fact that the exhaust gases arent directed away, so there can be no scavenging effect. Backpressure isnt the word you are looking for in this case, but I know what you meant, so it is all good.

visionary613 said:
Well whatever. lol. I really like this forum but even though I have four years of technical college in auto mechanics and motorcycle mechanics. And have worked in the field for over 6 years, I seem to always be wrong to most of you.:shrug: I guess Its the whole being a newb on the website. It's just funny how when ever I write something. I alway get 2 to 3 answers telling me how stuipid I am to think what I think Then later on in the post my points are made by someone else and accepted?:shrug: I guess you all went to better 4 year auto schools than me.:laugh: ( that sound passive agressive doesn't it, sorry)

By the way I am not upset at all just a little disapointed I cant ever really help. As far as Burning out the tops of the pistons, Yes thats possible. You DO need some back preasure( A high flow muffler is a great way to acheive that), And pulling out your cat does help to increase power. Like I said the first Time, I stand behind what I said.

Also mabey this is just the dynamic of a forum. I have not been on alot of forums.
Click to expand...

Funny, I went to college to to learn automotive and diesel mechanics, and I have worked in the field for over 10 years, plus I was pulling apart engines and transmissions since I was 10 years old. Hey, we can even top this discussion off by saying that I worked in an exhaust shop to get my start even. I also had ASE certifications in the diesel field..... so, take your passive aggressive stuff elsewhere. Especially since you will find there are a lot of mechanics on this board that have a lot more experience and training than I do even. Remember, many of us are older than you.

Maybe you should learn how exhaust really works before you try and tell us we are wrong. It isnt the fact that you are a newb, it is the fact that you are wrong in this case and spreading a very common old wives tale. Besides, you demonstrated your automotive expertise when you had to ask if it is possible to bore out fuel injected motors the same way you can do with carb'ed motors.

ALSO download firefox. Then you can have a spellchecker on your browser, and possibly make posts that are slightly closer to the english language
 
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That's a good one Find. The whole spell checker thing. That one has been used quite a few times to try and demean people on this forum. Here is the thing, I said that I was passive aggressive and said sorry. So take your elitist attitude and shove it. I get it you have more experiance than me. All hail Find!! Oh, by the way I am a very friendly person ask most the people in the northwest or bugzuki who knows me personally. For some reason you always jump down my neck, and it's getting old pretty quickly.
 
You misinforming people and misrepresenting yourself and your information to be accurate. This is the only time I really jumped down your throat. The other time I was just kinda laughing at you, cause I thought it was funny. Though, if you wanted me to jump down your throat on some of the stuff you said in that other thread, I could.

I didnt like your pity party comeback.

I also hate the poor spelling and bad grammar.

The means of communication on this forum are by typed words. Your spelling and grammar are one of the MOST important parts in this type of communication.

Imagine if you were to show up to a job interview wearing cut off jeans and a dirty sweat stained tank top. It wouldnt matter how much you know, the employer would think you are an idiot. Plus, it is incredibly annoying to have to read through horrible spelling and bad grammar.

If you know stuff, fair enough, pass on the knowledge and people will be grateful. If someone tells you that you are wrong, be sure you are right before you tell them they are wrong. If you find out that you are wrong, then congratulations, you learned something and you have more to offer.

I dont really care whether you are a nice guy or not, I can be a perfectly nice guy too, but when you come out with the passive aggressive stuff, and the whining, you are obviously not being a nice guy. What kinda response do you expect, I am not gonna pat your head and tell you that you are special and we shouldnt be mean to you. If you want that, go to your mom and ask her.

Anyways, I am done with you. Im not gonna be part of your temper tantrum, and I am not going to mess up this guys post any more. Have fun. Next time you want to try and convince people of your expertise, dont do it only a couple threads away from you asking people the basics.
 
sigh..... Well I don't want to fight with you I don't like to fight period. I understand you have been on the forum and herd alot of stupid things from people. Sorry If I seemed passive aggressive. That is not what I was trying not to do. I think forums are just a little out of my element. Btw I will go get firefox for the spelling.
 
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