Running no cat - 6G Celicas Forums

Running no cat

Jan 7, 2004 - 11:28 PM
Justin View Member Profile Enthusiast Joined Dec 13, '03 From Alabama Currently Offline Reputation: 1 (100%)	Tomorrow I'm going to get some custom exhaust pipe made for my celica. I was wondering how much louder it would be without cat. I am gonna have 2 1/4 in piping with no resonators and a muffler. Also, I heard that if you dont have a cat there will be a very noticable smell indicating you dont have one. Third, would it give me any hp gains since the midpipe would now be 2 1/4 Last, how easy would it be for a cop to tell that you dont have one. I live in alabama and we dont have to go through any emissions or vehicle inspections

Jan 7, 2004 - 11:49 PM
FallenHero View Member Profile Enthusiast Joined Dec 26, '02 From Alabama Currently Offline Reputation: 2 (100%)	NO WE DON'T welcome to the board! If you remove your cat it will sell like a rotten egg inside and out of your car. Either way it really won't do a whole lot power wise, in other words, the only place you will feal a difference is in your mind. On an old corvette, gutting the cat will make twenty hp. On a celica... one or two. Jon

Jan 7, 2004 - 11:52 PM
Coomer View Member Profile Administrator Joined Aug 23, '02 From Seattle, WA Currently Offline Reputation: 14 (100%)	I'd keep your cat on...you probably need it for backpressure reasons so that you don't lose torque. Also, your car will be very loud without a cat, and once you get pulled over for excessive noise, all a cop has to do is look under your car to see if you have a cat or not. -------------------- New Toyota project coming soon...

Jan 8, 2004 - 12:28 AM
Phat_99CeliGT View Member Profile Enthusiast Joined Aug 30, '02 From Ohio Currently Offline Reputation: 0 (0%)	Instead of removing the cat, get a header. It eliminates the cat. then get a high flow cat and have it welded in somewhere in the piping. I had a header to 2.5" piping to a muffler and it was LOUD and nasty. I just put a glasspack in and its a quieter car now. -------------------- Jared Harwell

Jan 8, 2004 - 9:28 AM
dcgoalie312 View Member Profile Enthusiast Joined Dec 20, '02 From OKC Currently Offline Reputation: 0 (0%)	i got my cat removed as soon as i got my car cuz i thought it was going to make it loud but it didnt. but there has never been the smell that you guys are talking about? DREW

Jan 8, 2004 - 9:44 AM

SpedToe169

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QUOTE

Instead of removing the cat, get a header.
It eliminates the cat.
then get a high flow cat and have it welded in somewhere in the piping.

That is an excellent idea.

I don't know where you're all getting this 'smell' business from. Its not going to smell if you take off the cat....have none of you ever driven a pre 1975 automobile? No cats there.

Coomer...backpressure is ALWAYS a bad thing!!

QUOTE

BACKPRESSURE = TORQUE?
An old hot-rodder's tall tale: Engines need some backpressure to work properly and make torque. That is not true. What engines need is low backpressure, but high exhaust stream velocity. A fast-moving but free-flowing gas column in the exhaust helps create a rarefaction or a negative pressure wave behind the exhaust valve as it opens. This vacuum helps scavenge the cylinder of exhaust gas faster and more thoroughly with less pumping losses. An exhaust pipe that is too big in diameter has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque.

Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and small pipe diameters. The only two exceptions to this are turbocharged engines and engines optimized for large amounts of nitrous oxide. Both of these devices vastly increase the exhaust gas volume and simply need larger pipes to get rid of it all.

Don't get rid of the cat, its irresponsible environmentally and won't gain you any power.

Jan 8, 2004 - 1:18 PM

Coomer

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QUOTE (SpedToe169 @ Jan 8, 2004 - 6:44 AM)

Coomer...backpressure is ALWAYS a bad thing!!

When racing, I'm sure it is, but when you're daily driving and not staying in the high RPM range all the time, don't you want more torque? If your exhaust is too big and you're running a naturally aspirated setup, I've read from so many sources that torque suffers from lack of backpressure.

--------------------

New Toyota project coming soon...

Jan 8, 2004 - 1:54 PM
Justin View Member Profile Enthusiast Joined Dec 13, '03 From Alabama Currently Offline Reputation: 1 (100%)	thanks for the advice I'll be keeping my cat

Jan 8, 2004 - 2:13 PM

Uppitycracker

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QUOTE (SpedToe169 @ Jan 8, 2004 - 7:44 AM)

Don't get rid of the cat, its irresponsible environmentally and won't gain you any power.

Exactly what I say when idiots talk to me about that as they call it the "cadillac Convertor"

QUOTE

Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and small pipe diameters. The only two exceptions to this are turbocharged engines and engines optimized for large amounts of nitrous oxide. Both of these devices vastly increase the exhaust gas volume and simply need larger pipes to get rid of it all.

And this is why I dont understand these poeple putting 3" piping with headers on a stock engine, talk about killing your low end, and not improving your high end period, it just seems like it because you ****ed up the balance of your engine and emptied your wallet for no reason.

Jan 8, 2004 - 3:34 PM
wind View Member Profile Enthusiast Joined Nov 4, '03 From Vancouver, Canada! Currently Offline Reputation: 0 (0%)	that rotten egg smell is the cat smell.... the cat has a chemical (some kinda of yellow stuff) sulfur.... all new cats smell like that... thats what i read in some mechanic article... not sure if thats correct....but it is the sulfur

Jan 8, 2004 - 3:43 PM

Uppitycracker

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QUOTE (wind @ Jan 8, 2004 - 1:34 PM)

that rotten egg smell is the cat smell.... the cat has a chemical (some kinda of yellow stuff) sulfur.... all new cats smell like that... thats what i read in some mechanic article...

not sure if thats correct....but it is the sulfur

Ya my mom just got a matrix and you get that smell sometimes, not very pleasant

Jan 8, 2004 - 5:45 PM

SpedToe169

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QUOTE

When racing, I'm sure it is, but when you're daily driving and not staying in the high RPM range all the time, don't you want more torque? If your exhaust is too big and you're running a naturally aspirated setup, I've read from so many sources that torque suffers from lack of backpressure.

No. I think you're thinking the right thing but calling it the wrong thing. Backpressure is ALWAYS ALWAYS ALWAYS bad. Anything you can do to get the air into or out of your engine more efficiently is good (when you have the proper amount of fuel to go with it). What isn't good is reducing the velocity of that air too much, thats what kills the torque. When you have a given flow through a tube and you increase the size (area) of the tube while keeping the flow rate the same, the velocity will decrease. All this moving air has an inertia. Since the flow rate stays roughly the same, the faster the air moves, the more inertia it has. This is what your engine relies on to help scavenge the cylinders and what creates the torque. A good exhaust system will strike a balance between the velocity and the flow losses due to the length and diameter of the pipe.

Sorry if that doesn't make sense or is disorganized....I've had a really bad day and its far from over....unless I finally get so pissed off that I quit my job and go home....

Jan 8, 2004 - 9:31 PM
Justin View Member Profile Enthusiast Joined Dec 13, '03 From Alabama Currently Offline Reputation: 1 (100%)	I just got my exhaust completed a ffew hours ago and im impressed. I paid 60 for the pipe (2 1/4") from the cat back I had them take off the secondary cat. Then i paid 100 for a nayos muffler. It sounds really good. nice and deep but not incrediby loud. I aso got a nice power gain through the whole power band and the top end kicks ass now. Its a good bit faster through the high rpms.

Jan 10, 2004 - 2:18 AM
Doge View Member Profile Enthusiast Joined Dec 2, '02 From Portland, Oregon Currently Offline Reputation: 0 (0%)	The purpose of a cat is to take away all the environmentally hazardous materials that come out of your engine. The gas passes through the waves or combs of the cat and mixes with chemicals that are fixed to the cat. The resulting chemical reaction turns the hazardous gases into safe gases. For example carbon DIoxide is safe...carbon MONoxide is hazardous...a simple chemical reaction can change one to the other. i dont know for sure the gases that come out of an engine...so dont qoute me on the cabon monoxide thing...it was just for example purposes only This post has been edited by Doge: Jan 10, 2004 - 2:19 AM

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