Benefits of Removing Cat and Running Straight Pipe?

[black2yaris]

Originally Posted by Joker

Less backpressure is better, NONE is not...by putting 2 1/2" pipe on any of our normally aspirated cars is overkill in every sense of the word. If you think your car is slow now go ahead and try it.....

To clarify I assume when you say "no header at all" you mean the engine was tested w/its stock exhaust manifold? The only other meaning would be the car had no exhaust manifold at all, esentially running the cylinder head "open" which makes no sense.

A header w/a good design should make some gains on our cars, when I say good design that doesnt mean the 4 into 1 DC header that recently came out. 4 into 1's are for higher (5000+ rpm) applications which means on the lower end your dead...unless of course you drive around at or near redline all day. Do some research, DC's own website highlights this fact! Just trying to help out the inexperienced. Peace.....

: clap:





thanx for clearing that up & saving some people on this thread/YW some cash on useless exh.systems
..can you give us your opinion on what is a good set up for exhaust on our Yarii ....
some here want a fart can with sound ,
some of us want to improve preformance on a Yarii with in reason on a street car,
some want a Yarii they can weekend track with,
then some are just Ricers
.... any advice is welcome Thanx in advance

[largeorangefont]

Originally Posted by black2yaris

: clap:





thanx for clearing that up & saving some people on this thread/YW some cash on useless exh.systems
..can you give us your opinion on what is a good set up for exhaust on our Yarii ....
some here want a fart can with sound ,
some of us want to improve preformance on a Yarii with in reason on a street car,
some want a Yarii they can weekend track with,
then some are just Ricers
.... any advice is welcome Thanx in advance

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

[kurokoma-kun]

Originally Posted by largeorangefont

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

What is your opinion of the one etimago is proposing for GB?
http://www.yarisworld.com/forums/showthread.php?t=9047

[AlphaFox]

Originally Posted by BailOut

The catalytic converter serves many valuable purposes, but mainly the severe reduction of noxious emissions. Not only does this greatly help the environment but it is also mandated by Federal law.

To remove it is one of the most irresponsible and selfish things an automobile owner can do, and it is my sincere hope that anyone that does so gets caught and punished for it.

I dont get it. obviously you people know he knew the environmental effects of it and doesnt care, he is just wondering performance benifits. WHY are you all blabbing about the NOX and crap that might come out of the exhaust, he doesnt CARE and spescifically stated NOT to post things like this. why post in a thread if the author of it says he doesnt care about that..??

that said, I a agree not running a cat is kind of dumb, for one it REEKS if your driving behind someone and they arent running a cat.

[joey1320]

Originally Posted by Joker

Less backpressure is better, NONE is not...by putting 2 1/2" pipe on any of our normally aspirated cars is overkill in every sense of the word. If you think your car is slow now go ahead and try it.....

To clarify I assume when you say "no header at all" you mean the engine was tested w/its stock exhaust manifold? The only other meaning would be the car had no exhaust manifold at all, esentially running the cylinder head "open" which makes no sense.

A header w/a good design should make some gains on our cars, when I say good design that doesnt mean the 4 into 1 DC header that recently came out. 4 into 1's are for higher (5000+ rpm) applications which means on the lower end your dead...unless of course you drive around at or near redline all day. Do some research, DC's own website highlights this fact!

Just trying to help out the inexperienced. Peace.....

T

no i meant no header/manifold at all. just open exhaust out of the head.
i'll try to find the mag. around the apartment somewhere but not sure if it will still be around, since its an old mag.

and yes they did make more whp/tq with nothing connected to the head... i'm not a designer/engineer so i'm not sure as to how/why but it did...

[alhope34]

Originally Posted by joey1320

and yes they did make more whp/tq with nothing connected to the head... i'm not a designer/engineer so i'm not sure as to how/why but it did...

Probably more top-end torque? I am absolutely positive there is low end torque lost if there is not enough back pressure.

[largeorangefont]

Originally Posted by kurokoma-kun

What is your opinion of the one etimago is proposing for GB?
http://www.yarisworld.com/forums/showthread.php?t=9047

There is no info on piping diameter, but the price sounds good :)

[Black Yaris]

Originally Posted by largeorangefont

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

I agree, but I recommend 2.25... I had the 2 inch at first and noticed a gain, but was not happy with the muffler. so I decieded to say hell with it and go 2.25 mandrel from the cat back with a new res and a flowmaster, and that made a HUGH difference though out the whole RPM range... IF I lost anything in the low end (i doubt I did) it was not felt and the gain out weighted the loss

[WolfWings]

Originally Posted by BailOut

Either I was misinformed at the testing station I asked lot of questions at, or Wikipedia is wrong. Either scenario is highly possible.

The end result is the same regardless, though:

Catalytic converter == good, hence why it is mandatory in most parts of the developed world.

No catalytic converter == acid rain, contaminated water, etc.

Nah, I'll disagree with you.

Low emissions == good, yes. But catalytic converters are just the easy way to 'force' all emissions down quickly, ergo why they were made basically manditory.

The Honda Civic was created initially to avoid having to add a catalytic converter (CVVC was the original engine-tech nickname, ergo the series-name CiViC) for example, and I've run vehicles with the Cat removed that still passed the tailpipe-sniff test just fine as long as they were well-tuned and well-maintained.

[loafer650]

Originally Posted by Nexus1155

Just wondering what everyone thinks of cutting out the cats and running straight pipes. Will it add more power, because of it being more free flowing(I know its not a turbo vehicle but hey). Will it sound nicer or more annoying, does anyone have any vids or sound clips. Any comment is appreciated...

I don't have to worry about inspection or anything and global warming is BS so please no tree hugging splurs... It's not that I don't care about the environment I yell at people for littering.

1. as i stated b4 running straight pipe will definately improve performance and sound.. so long as you dont mess with the size of ure pipes... ill say it again..backpressure is your friend.

2. you would only need larger pipes if you doing a turbo or supercharger set up..

[WRXGUY02]

Unless you have a forced induction vehicle don't even think about removing or gutting the cat. It will do nothing but hurt the enviroment and possibly make you lose hp or torque. Your engine is designed and tuned from the factory to have a certain amount of exhaust backpressure. If you change that it affects everything from how exhaust pulses exit the cylinder to combustion in the chamber. You need a certain amount of backpressure for the car to run correctly. Lets face it. If you bought a Yaris you didn't plan on having a fast car. That is unless you are planning on adding some form of forced induction. Even then.. It probably won't be really that fast. Faster than it was but without some kind of major engine overhaul and engine management you're not gonna beat too many things these days. Don't get me wrong. I respect the idea of modding a car. My Subaru has over 350AWHP and I love it. But you buy cars for what they are good at. The WRX is a AWD Performance Car. The Yaris is a FWD Economy car and there is nothing wrong with that. I am on this forum because I am about to buy a Yaris for my daily driver. I think they are great cars for what they were made for. Without a crap load of money invested there probably won't be too many fast Yaris's out there. Now.. onto the emissions lesson.

Gasoline Engines only produce a few harmful emmisions that are tested for.

HC- Hydrocarbons aka non completely combusted fuel
CO- Carbon Monoxide
NOx- Nitrogen Oxides- It is not Noxious Emissions as stated by another one of your users.. NOx is a deadly gas produced above 2500degrees F. Your EGR system in most vehicles is designed to help combat NOx. It would be a whole different lesson on how the EGR works.
CO2- Carbon dioxide- A properly working exhaust system will produce about 14% CO2.

Your Catalytic Convertor combats these emmisions.There are several chemical compounds and materials in the Cat that make is work. If anyone has ever had a cheap narrow band air/fuel sensor they see how your ratio is constantly going from rich to lean to rich very quickly. It actually switches about 10 times faster than the gauge shows. When you go to WOT the ECU automatically goes to rich. Your Cat fights emissions differently during different conditions. When the engine is rich the cat battles one emission and when the engine is lean it battles another. The target average between the two sides is 14.7 AFR. That is the ideal ratio to battle all the emmisions properly.

Bottom line is I felt I had to write this because I see a constant amount of bad information being written. I had to give people some proper direction. If you are trying pick up a few HP from removing the cat on a NA Yaris then you really are wasting your time. The money and time involved won't gain you any real results. Now if you are going forced induction it may help to remove the factory cat but I would replace it with a high flow. Just remember that no matter what you do that altering a working emmisions system is a Felony. The last time I checked it was like a $10,000 fine plus possible jail time. Remember I am not bashing Yaris's or their owners what so ever. I think they are great little cars and I look forward to owning one. If anyone has any other questions feel free to ask.

[largeorangefont]

Originally Posted by WRXGUY02

Unless you have a forced induction vehicle don't even think about removing or gutting the cat. It will do nothing but hurt the enviroment and possibly make you lose hp or torque. Your engine is designed and tuned from the factory to have a certain amount of exhaust backpressure. If you change that it affects everything from how exhaust pulses exit the cylinder to combustion in the chamber. You need a certain amount of backpressure for the car to run correctly. Lets face it. If you bought a Yaris you didn't plan on having a fast car. That is unless you are planning on adding some form of forced induction. Even then.. It probably won't be really that fast. Faster than it was but without some kind of major engine overhaul and engine management you're not gonna beat too many things these days. Don't get me wrong. I respect the idea of modding a car. My Subaru has over 350AWHP and I love it. But you buy cars for what they are good at. The WRX is a AWD Performance Car. The Yaris is a FWD Economy car and there is nothing wrong with that. I am on this forum because I am about to buy a Yaris for my daily driver. I think they are great cars for what they were made for. Without a crap load of money invested there probably won't be too many fast Yaris's out there. Now.. onto the emissions lesson.

Gasoline Engines only produce a few harmful emmisions that are tested for.

HC- Hydrocarbons aka non completely combusted fuel
CO- Carbon Monoxide
NOx- Nitrogen Oxides- It is not Noxious Emissions as stated by another one of your users.. NOx is a deadly gas produced above 2500degrees F. Your EGR system in most vehicles is designed to help combat NOx. It would be a whole different lesson on how the EGR works.
CO2- Carbon dioxide- A properly working exhaust system will produce about 14% CO2.

Your Catalytic Convertor combats these emmisions.There are several chemical compounds and materials in the Cat that make is work. If anyone has ever had a cheap narrow band air/fuel sensor they see how your ratio is constantly going from rich to lean to rich very quickly. It actually switches about 10 times faster than the gauge shows. When you go to WOT the ECU automatically goes to rich. Your Cat fights emissions differently during different conditions. When the engine is rich the cat battles one emission and when the engine is lean it battles another. The target average between the two sides is 14.7 AFR. That is the ideal ratio to battle all the emmisions properly.

Bottom line is I felt I had to write this because I see a constant amount of bad information being written. I had to give people some proper direction. If you are trying pick up a few HP from removing the cat on a NA Yaris then you really are wasting your time. The money and time involved won't gain you any real results. Now if you are going forced induction it may help to remove the factory cat but I would replace it with a high flow. Just remember that no matter what you do that altering a working emmisions system is a Felony. The last time I checked it was like a $10,000 fine plus possible jail time. Remember I am not bashing Yaris's or their owners what so ever. I think they are great little cars and I look forward to owning one. If anyone has any other questions feel free to ask.

So its ok to remove all cats on a WRX but not on a Yaris? That makes no sense. A catless Yaris will pollute about half or less of what a catless WRX will.

You lesson is about half correct. Keeping the AFR at 14.7:1 is not some "emission balance", it is chemistry, specifically it is Stoichiometry. It is the point at which 100% of fuel and air is used in a given reaction. In this case that reaction is the combustion process. Because byproducts of combustion such as heat are created, cars need to be run richer than 14.7:1 under load to keep the engine from destroying itself.

Your cat works better the hotter it is. Above 1600 degrees the cat can melt or burn up, which is bad. If your car is tuned to rich, the cat won't get hot enough to work properly, and could become clogged.

Your narrowband example in not valid. The car is not actually making wild swings in fueling. The narrowband gauge does that because it is taking a reading from a vary narrow voltage window. Anything below is rich, anything above is lean. That is why you use wideband sensors for tuning.

Removing the cats on a Yaris WILL get you 1-2 HP. Every engine mod you do to a Yaris except FI gets you a couple HP. If the car is catless, it will smell and stoplights, and you may not like that. Hi flow cats are a good alternative, and you will still keep the HP gain, and most likely pass a smog test. Contrary to what you said, removing the cats does not remove all back pressure and make the car lose power.

If you installed a 3 inch catless exhaust system on the car, then yes, you would lose too much backpressure and feel a loss in low end power, but no one is doing that.

[Jeepman28]

wow I just traveling the interwebs and ran across this I know it is a bit old but I just have to laugh at all of you,

One: you all own a f'ing Yaris, really who own those pieces of crap!
Two: The guy that started this thread hit it on the head when he said that Global Warming is BS. It is made up to do this shit, make us buy shit for our cars and homes that don't need to be there, or go out and buy a new car because it is "Cleaner"
Three: A Motor is like a big Air pump that more air up push though it the faster and stronger she will be, "remember the muscle car races from the big Three bigger motors that sucked as much air as possible and pushed it out just as fast. I got rid of My Cat. when I got my ZJ and shorten my pipe and put on a 3.5in upgrade, plus I ripped out all the computer crap and put a crab in replace of the EFI I haven't been happier, And to top it off I drive over yaris's and other shitty Toyota's on the weekend.

[3cyltrbo]

Originally Posted by Jeepman28

wow I just traveling the interwebs and ran across this I know it is a bit old but I just have to laugh at all of you,

One: you all own a f'ing Yaris, really who own those pieces of crap!
Two: The guy that started this thread hit it on the head when he said that Global Warming is BS. It is made up to do this shit, make us buy shit for our cars and homes that don't need to be there, or go out and buy a new car because it is "Cleaner"
Three: A Motor is like a big Air pump that more air up push though it the faster and stronger she will be, "remember the muscle car races from the big Three bigger motors that sucked as much air as possible and pushed it out just as fast. I got rid of My Cat. when I got my ZJ and shorten my pipe and put on a 3.5in upgrade, plus I ripped out all the computer crap and put a crab in replace of the EFI I haven't been happier, And to top it off I drive over yaris's and other shitty Toyota's on the weekend.

ROFLMAO.

This right here (post above), is reason enough for higher education.

Will

[1.5]

He wasted all his time registering and creating an account and reading this thread just to post that?

[malibuguy]

Back pressure is evil in any amount.

However no use polluting the world more then we have to. Thats why my race car will have a cat again...i do currently dont have one on it for testing purposes.

[tomato]

Originally Posted by 1.5

He wasted all his time registering and creating an account and reading this thread just to post that?

+1

Don't feed the trolls.

[07stlYaris]

Holy crap what a bunch of mis-information the emissions nazis have perpetrated on the public. As for NOX, It stands for Oxides of Nitrogen and that's fricken it! None of the other crap falls under NOX. As for Carcinogens WTF???? There are more carcinogens in Broccoli from Brazil than from out of a Yaris tailpipe. What a load of crap. As for Catalytic converters, I have them on all 4 of my cars because they are REQUIRED in about 90% of cities in the US and I never know where I'm going to live so I keep them. The Chinese burn tires for heat, In the Phillipines they burn entire forests for farming. I agree that pollution is a bad thing but so is the pollution of bad information and the fools that spread it. Al Gore is an idiot, plain and simple. For the USA to be blamed for the third worlds destruction of the earth is outright stupid. We are made to suffer for the transgressions of others???? We drive the most efficient cars...have the most responsible laws regarding environmental protection...we take care of our animals better than some countries take care of their citizenry and we have douchebags on this forum pontificating about how bad it is to remove a catalytic converter. Go to your favorite country and get the hell out of my USA I say to you. We are waaaaayyyyy better than ALL other countries with regards to taking care of the earth.