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Discussion Starter · #1 ·
Let me start of by saying i'm happy because i finally got my florida plate and registration which means NO MORE INSPECTIONS YAY! well, i've come across a dilemma which is wether to go with a high flow cat,a hollowed out Cat or no cat at all. Now i've spoken to some friends and fellow racers and i've gotten different responses. I just can't decide. I'd like to go with a straight pipe because as my name says i do have future plans for a turbo system which would require a straight pipe exhaust but i don't want to get hassled by some asshole cop who decides to look under my car and not find a catalytic converter which would mean REALLY BIG FINE!! I've been told that a hollowed cat might be bad because despite being "like" a straight pipe there's still room for the air to bounce around in the cat causing a restriction. Also i feel that with a high flow cat, i won't have as much of an air flow as with a straight pipe. I need advice.
 

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How about you get a high flow cat? It will produce about the same HP, that way there is no way you can get fines and you help our ever decreasing atmosphere while your at it. If you have to chose, then go straight pipe, like you said a hollowed cat will actully make you lose hp. But honestly a high flow cat, will yeild close to the same gains as a straight pipe but be much better in many other ways.
 

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NegroDamus said:
hollow cat = free.99

Your that retarded aren't you? You lose HP with a hollowed cat!!!!!! let me expalin this to you another way...if any given car is pushing 170hp(does not make crank or wheel) with a cat in tact...and then you hollow that same cars cat, it will probably only produce around 155-160hp. So why in the hell would you hollow for free99? Like i said above a hollowed cat loses hp.

On a side note, it is people like you that make us have federal laws in place to save our world!!!!!!!!!
 

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ALL C5 said:
Your that retarded aren't you? You lose HP with a hollowed cat!!!!!! let me expalin this to you another way...if any given car is pushing 170hp(does not make crank or wheel) with a cat in tact...and then you hollow that same cars cat, it will probably only produce around 155-160hp. So why in the hell would you hollow for free99? Like i said above a hollowed cat loses hp.

On a side note, it is people like you that make us have federal laws in place to save our world!!!!!!!!!

Spare me, please..

You have been spouting opinion based "facts" for years, until you can prove me wrong. Ill take that comment as an Opinion. :rolleyes
 

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NegroDamus said:
Spare me, please..

You have been spouting opinion based "facts" for years, until you can prove me wrong. Ill take that comment as an Opinion. :rolleyes

Do you understand how an exahust system works?

there are two main enemys in an exahust backpressure and turbulance.

I am not going to go into either, but both mess up flow veloccity of the exhasust exiting the car. When you hollow a cat, you create mass amounts of turbulance, which really screws with flow velocity, thus losing HP.

Also a hollowed cat will cause a car to lose flow velocity, thus hindering performance.

Here is one thread, by two people who have very good car knowledge and they say it would hinder performance as well, there is alot chit chat in it but it backs up what i say and it goes into the back pressure issue.

http://www.superhonda.com/forum/showthread.php?

t=25880&page=3&pp=15&highlight=hollowed+cat

Here is another article, talking about test pipe vs. high flow cat, it does not go to my piont about a hollow cat, but it shows that if you run a hi-flow cat you have many more pros then a test pipe.

Like i said NegroDamus, it is people like you that we have millions of tax payer dollars to have laws enforced and kpet in place. We would all be fucked if we had the 3 year old mentality that you do on hey its free thats the best reason to do it.


There are no real dyno charts out there showing a hollowed cat vs. a test pipe or a normal cat, because people do not want to spend the time to hollow a cat and then test it, just to prove exhaust flow velocity knowledge right. Why don't you prove me wrong since you want to call me out.

Some food for thought, there was a time when the most "knowledgable" people in the world, knew that the world was flat, and Columbus knew it wasn't...and well we know our world is not flat...
 

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All I posted was free.99.

You have still not proven anything.

Yea, people like me create emissions laws. :rolleyes When anyone who has anything performance is ruining the atmosphere. 2 stroke dirt bikes polute more than a turbo civic.

Whatever you say TODA.
 

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why not go with straight pipes and just tack weld the shell of your cats in that area of ur pipe. sure it might add a bit of weight but if it will fake it and save u some potential fines why not do that?
 

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NegroDamus said:
All I posted was free.99.

You have still not proven anything.

Yea, people like me create emissions laws. :rolleyes When anyone who has anything performance is ruining the atmosphere. 2 stroke dirt bikes polute more than a turbo civic.

Whatever you say TODA.

you really are that stupid...

they are now stopping production of two stroke bikes, w/ replacement of 4-stroke, for emissions reasons, because somebody has said, "We need to do something about the 2-strokes, they put out to many harmful chemicals, if we had people like you that said it is cheaper not to create Tech. to prevent harmful toxins getting into the air, we would be in alot of trouble as a world." Just like ULEV and everything else with that, in place of the old v8's. It takes time, and people unlike you to fix the problems and prevent the destruction of our planet.

I am done arguing with you, mainly because a brick is smarter then you are, and I have wasted to much time on you already.
 

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Ok a couple things.
1. I honestly think that the atmosphere is fucked up because of planes and other large vehicles(buses,semi's,construction vehicles) that don't have to pass smog. Not all of the everyday other cars on the road. Well maybe the muscle cars that get like 3mpg.

2. Have you ever looked inside of a cat? It's a bunch of fuckin catalyst honeycomb shit in the way of the exhaust flow. How's that for turbulence and losing power. Let's start from the the exhaust ports. Ok, air is coming out, flowing nicely through the primaries of the header, and then BAM a fuckin wall of catalyst honeycomb. Sounds like some restriction and turbulence to me. I personally have a gutted cat and it sounds like shit, but it feels less restricted. It was a carsound high flo to begin with and I gutted it out one day; you wouldn't belive how much bullshit came out of it. It does sound like shit and I don't notice a whole lot of gain from it, and miss how my car used to sound, but it was free and gave little gains. I think a straight pipe would be the best bet because it's a straight path all of the way through.
 

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wow i didn't know that this forum was full of n00bs..

ALL C5 is right... NegroDamus is wrong

if you are thinking that hollowed out cats will yield performance.. you are sadly mistaken. i won't go into the details (because im so fuckin lazy) but trust me.. hollowed out cats will hurt not only the performance of the vehicle but the env as well.
 

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ok..i feel a little bad so i'll just explain briefly

key to having a great performing exhaust is having little backpressure while having high exhaust velocity. hollowed out cat will prevent achieving that because the cat itself is much bigger than the exhaust piping. a hollowed cat is more of a chamber which disrupts the exhaust flow velocity. not only will it dramatically reduce the exhaust flow but it can also create reversion which is really bad...
an ideal exhaust setup would use the "stepping" method. what is stepping?
for example.
from a 2" header collector to a 2.25" high flow cat to 2.5" muffler... this will prevent reversion and have the highest exhaust flow velocity

however if you have a hollowed out cat.. this is what your setup would look like compared to the top
2" header collector to a 3"~4" hollowed cat.. to a 2.5" muffler... just logically you can see that something is not right.. first it will cause reversion and the exhaust flow will reduce dramatically...

so my point is.. DO NOT hollow out your cat unless you want your car to run like shit and damage your engine.. if that is what you want.. by all means.. please do so.
 

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culmination said:
wow i didn't know that this forum was full of n00bs..

ALL C5 is right... NegroDamus is wrong

if you are thinking that hollowed out cats will yield performance.. you are sadly mistaken. i won't go into the details (because im so fuckin lazy) but trust me.. hollowed out cats will hurt not only the performance of the vehicle but the env as well.

explain yo self playa....
and *****, im sorry dood..
 

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I fully understand how the whole flow thing is getting disrupted.

I hollowed mine about 5 years ago. So its run on 4 different engines within thoes 5 years. I have never noticed any negative effects from it bieng hollow. I wouldnt do it again just becasue its pointless. The butt dyno cant tell the difference.

My car has run just as good as it did before I did it up until now. So the whole you car will run like shit is an overstatement.

The only reason I said Free.99 is becasue it was half smartass and half its free. Yes hollowing a cat is ghetto but oh well. My car runs fine, its not slow and my dumbass at 16 would have sworn "I can feel the difference". If it was true or not doesnt matter, But I know for sure that it did NOT run worse than it did 20min before I did it.

So in the end any gain you would get from hollowing it out, will be countered by the turbulance it creates, but IMO you WILL NOT LOOSE ANY NOTICEABLE PERFORMANCE, and until one of you dynos a car with a stock cat and a hollow one its all theory. (no one will dyno so its a pointless argument).

DONT HOLLOW YOUR CAT BECAUSE ITS A GHETTO THING TO DO AND YOU WILL GET FLAMED FOR IT :rolleyes

lol oh yea, yellow be stalkin me :hehs
 

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if it is just a theory why is it that people use the term "reversion" and "stepping" so frequently? believe what you want.. because after all, some people believe putting an aftermarket intake nets 15+whp gain on a stock civic.
 

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Let me get this right. Im basicly a "noob" because I dont belive that hollowing out a cat will cause a SIGNIFICANT loss of power?

I said you are getting nothing from hollowing it, only that I dont belive you are going to loose a noticeable amount of power and the car will run like shit.

Why is my car NOT running like shit then?
 

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Discussion Starter · #20 ·
i just wanna say thanks to culmination and hybrid, i had read about reversion and stepping in this book i purchased, maybe you guys have heard of it, it's called Honda/Acura Engine Performance. I appreciate all of your feedback. Call me a newb for learning from a book i don't care, i don't have the money time and space to learn by breaking shit, so the best thing i can do is ask you guys and some racers that i know for some input and read what i read. But thanks to all, your feedback is greatly appreciated! I think i'm gonna go with a straight pipe and a cat shell tackwelded around it. i'd like to go with stepping but i think it'd be much more inexpensive if i tackweld the cat shell around a straight pipe for bacon evading purposes catch my drift? LOL!
 
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