Benefits of Removing Cat and Running Straight Pipe?

[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.

[redduck]

you might lose
compression

[YarisTom73]

Plus, it will sound like a crappy motorcycle, from wht I've seen; also, I can't imagine there's much HP to gained from this. Between noise and environmental concerns, I really don't see the sense in doing this. But then, I rarely see sense in anything :biggrin:

[black2yaris]

Don't u run the risk of burning the exhaust valves with no back pressure with a straight pipe ? as they would heat up to much ...

[Nexus1155]

ahhh then no go then thats all i wanted... now what if i downsized the exhaust!!! more compression muahahaha.... pure NA POWA

[death is my gift]

Power? You're driving a Toyota Yaris.

Just sayin.

[Vic-2NZFE]

I have seen a lot of 4 Cyl cars running straight pipes and believe me if this is done right there si no way you will loose compression so go figure.

[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.

[PetersRedYaris]

...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.

:clap: :clap: :clap:

[Astroman]

On my turbo lebaron I upgraded to a 3" exhaust and kept the cat. You can get performance cats that filter out the emissions their supposed to while providing high-flow. I purchased one for cheap on ebay from a seller that sold catco brand. Worked great. There is NO testing where I live, but I wanted to keep it legit.

[Vic-2NZFE]

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.

This is true also :respekt:

[alhope34]

A lot of people around here with loud mufflers on their civics get their exhaust shops to cut a hole at the top of the cat and hollow it out then wield the top back on so from underneath unless you look really close, it looks normal. But really inside it's just a straight pipe through the cat's outer shell.

In Ontario we have really strict emissions testing, but it isn't too hard to get emissions faked. When I got my first car I didn't know it was so badly beat up as it was, and I was told by a few mechanics the best and easiest solution to solve the emissions problem was to get a new car, which I couldn't do. When I ran out of temp plates the DMV would give me, I finally had to get the papers done. Still had the car 4 months after that till it totally died. I even replaced the cat on that car and ALL of the o2 and no2 sensors on the exhaust...still didn't fix the emissions. Kept failing on what the place called "nox". Limit was 200 and something and my car was doing in the 2500's

[BailOut]

Kept failing on what the place called "nox". Limit was 200 and something and my car was doing in the 2500's

"Nox" is short for "noxious emissions". Gasoline-burning vehicles produce 3 kinds of emissions:

1) GHG (greenhouse gases - Carbon Dioxide and Nitrous Oxide)

2) Nox (noxious emissions - Nitrogen Oxide, Carbon Monoxide, Sulfur Dioxide, various carcinogenic (cancer-causing) hydrocarbons... all the stuff that acid rain is made of)

3) Passive (paint flakes and fumes, leaking fluids, etc.)


A catalytic converter helps mostly with the "nox" group.

[Black Yaris]

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.

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.

:clap: :clap: :clap:

Yes, that ment your two morons.... obviously he does not care your opinion.
I was going to wait to go catless, but just because of that comment from Brian/BailOut, I am getting them bitches cut out and throwin another resinator in. I wish I lived near him, I would blow those noxious emissions right on his door step.

[Black Yaris]

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.

BTW... I think Vanderkitten is running a race pipe on one of his Yarii... I would shoot him a PM

[alhope34]

"Nox" is short for "noxious emissions". Gasoline-burning vehicles produce 3 kinds of emissions:

1) GHG (greenhouse gases - Carbon Dioxide and Nitrous Oxide)

2) Nox (noxious emissions - Nitrogen Oxide, Carbon Monoxide, Sulfur Dioxide, various carcinogenic (cancer-causing) hydrocarbons... all the stuff that acid rain is made of)

3) Passive (paint flakes and fumes, leaking fluids, etc.)


A catalytic converter helps mostly with the "nox" group.

My car failed harder with the new cat. And I even drove it 500km before I got it re-tested. got 1000 or so with the old cat that was all clogged. And yes, the new cat was also a three-way. I know two way cats don't work as wekk

[umm_bacon]

Yes, that ment your two morons.... obviously he does not care your opinion.
I was going to wait to go catless, but just because of that comment from Brian/BailOut, I am getting them bitches cut out and throwin another resinator in. I wish I lived near him, I would blow those noxious emissions right on his door step.

Emissions Nazi!

[alhope34]

Yes, that ment your two morons.... obviously he does not care your opinion.
I was going to wait to go catless, but just because of that comment from Brian/BailOut, I am getting them bitches cut out and throwin another resinator in. I wish I lived near him, I would blow those noxious emissions right on his door step.


Haha, I like your response.

[Nexus1155]

Oh Black Yaris you're my hero I was skepticle on commenting on a couple other peoples in thoughts of getting trees bashed over my head or something, but if what people say is true that it will lower the compression and create a downgrade in performance i would not want to do that per say, but i will toss him a PM and see what he says too....

[alhope34]

Well from what I know, USUALLY a free-flowing exhaust will free up a few extra top RPM hp but will take low end torque away. The Yaris's low end RPM range is already bad enough for power/torque without taking more away form it. That's just my opinion, though.

[Bdaslug]

I gutted my cat. and also I made my piping larger than stock. now I have a 2.5 in exhaust all the way. without the cat it's get a little bit louder. Depending if you have a straight through muffler like a N1 style. But it doesnt sound like a honda. Also your gas mileage will go down alot, Because the check engine light stays on without the cat. I actually tried both O2 simulators (mechanical and electrical) and the check engine light still comes on after a few miles. But you can feel the difference from the stock 1-3/4 inch to 2-1/2inch piping only at higher speeds. I am going to install a high flow cat to get rid of the check engine light and it should help my gas mileage a bit.

[eTiMaGo]

If you have a dedicated track race car, then maybe, yeah. But for a car that will spend most of its time on public roads, you really should consider other people's ears (and lungs). I'd recommend you get the cat replaced for a less restrictive high flow one, it would be an ideal compromise.

[loafer650]

you can run straight pipe...but dont change size of pipes..backpressure is your friend....

[acdaazn]

Not really trying to be an emission nazi or anything.... but putting out so much nox and slowly killing trees off is just going to make your life worse. Everything comes with a chain effect.

Trees, especially elder trees, are like air conditioners that are on for 10 hours a day. The less tree we have, the worse it becomes for us. Then we would have to resort to A/Cs; making electricity more of a scarce resource than it is now. Oil prices goes up along with that, then that would reflect on to your gas bill. Yes, I know you drive a Yaris. But the point is, why would you want to be a part of it for that "at most 5 hp" gain?

[Nexus1155]

Eh, im probably not going to do it for the simple fact it will toss a CEL and kill the MPG because it cant give proper o2 readings, but acdaazn do you have a blown up picture of your sig?

[blueskana]

High flow cats are pretty damn high flow... seriously, you can practically see right thru them, yet they allow for burning of "evil" gasses. Considering if you ran one right after your header and then ran straight pipe back it would pretty much have all the benefits of a thru-system, no CEL, hippie approved and emmisions/inspection good too along with the power... plus it's something to show the cop and say "Eh, I got's me a cat rite theh'!".
Good luck with whatever you run. A full exhaust is on my plate too once I figure out how exactly I want to do it.

[WolfWings]

"Nox" is short for "noxious emissions". Gasoline-burning vehicles produce 3 kinds of emissions:

No, incorrect, wrong, wrong, wrong. As wrong as claiming Annie Lennox wrote a song about walking on propane gas.

nox stands for a single chemical family being tested for: Nitrous OXides.

Petrol-based engine emissions-testing systems aren't even remotely categorized like you listed. The 'bad chemicals' they produce are:
Nitrous OXides (two Nitrogen atoms and a random number of Oxygen atoms)
Carbon Monoxide (two Carbon, one Oxygon)
Unburnt HydroCarbons (one Hydrogen, one Carbon) actually.


These (NOX, CO, HC) are what are tested for in a tailpipe test, also. A three-way cat converts NOX better if you're running a rich mixture, or converts the other two better if you're running a lean mixture. Basic chemistry, replace a cat, adjust the fuel mixture and you can pass an emissions test almost always. California is so hard to pass because of their inspections, which include the most common ways to adjust the fuel-mixture having to be factory-spec.

At least research your claim a little (http://en.wikipedia.org/wiki/Catalytic_converter#Three-way_catalytic_converters) before spouting it off like it's gospel, 'kay? :wink:

[BailOut]

At least research your claim a little (http://en.wikipedia.org/wiki/Catalytic_converter#Three-way_catalytic_converters) before spouting it off like it's gospel, 'kay? :wink:

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

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.

[Nexus1155]

ahhh you see, but it doesn't effect Ozones! so the big thing is a lie ! it all gets soaked into the atmosphere and clouds... not up way past there and burn holes like wut! purely scientfic! zomg ... Americas way of scaring idiots to try and get more moneys!

[eTiMaGo]

ahhh you see, but it doesn't effect Ozones! so the big thing is a lie ! it all gets soaked into the atmosphere and clouds... not up way past there and burn holes like wut! purely scientfic! zomg ... Americas way of scaring idiots to try and get more moneys!

Ozone? I don't think anyone brought that up before, but it's got very little to do with exhaust fumes.

BTW as WolfWings mentioned:

. A three-way cat converts NOX better if you're running a rich mixture, or converts the other two better if you're running a lean mixture

This is very true, the ECU, in our cars at least, keeps oscillating the mixture between rich and lean in order to maximize the efficiency of the cats :smile:

Anywayy, as I said before, it's just irresponsible to have a daily driver without a catalyzer :wink:

[Joker]

As I sit back and read this post I wonder what some of the people think they will gain by either removing the cat or going to huge (at least for our cars) 2 1/2" exhaust pipe? Like someone said in this thread some backpressure is good, take it all away and you lose your bottom end. For most of us losing your bottom end means more sluggish acceleration, etc. Most of us dont tool around in the 5000 rpm + range all the time.

If solid gains were expected and proven by removing the cats or going to larger pipes then by all means I'm in but the reality is that on newer vehicles the cat isnt as restrictive as most people think.

I have a long history of drag racing both cars and motorcycles. There is no new magic here, our cars are normally aspirated and will benefit from the normal bolt on parts such as header/intake/exhaust IF chosen wisely. More air in + more air out = better performance. This is the same thing people did back in the old days, replace stock exhaust manifolds w/headers, replace small carbs with larger ones, etc.

The only thing we need to contend with is the ECU. If you feel you must override the stock ECU there are options such as the E-Manage and if you have the need to go full stand alone then there is Haltech and the like.

I appreciate this forum as it provides feedback from real people on many of the things we like to do which for most of us is to mod their car. Just givin' my 2 cents here....have a good morning....

T

[joey1320]

you are not lowering compression you are lowering backpressure.
the compression is inside the engine, inside the cylinder and the head. thats where the compression is rated.

the less backpressure the better on any engine. scc did a test years ago about all the aftermarket headers for hondas and none of them made any more whp than no header at all. all thru the rpm band, the no-header run made the most horsepower and torque.
(i'll see if i can find the mag somewhere...)

the only reason why people burn valves when using open headers, no cats, test pipes and what not, is that the car wasn't tuned properlly after the removal of these parts and the car ran lean, since you are making more power.

theres really no reason for you to remove the cat. converter on any car. try to make clean power other ways and keep the cat. for last...

[Joker]

the less backpressure the better on any engine. scc did a test years ago about all the aftermarket headers for hondas and none of them made any more whp than no header at all. all thru the rpm band, the no-header run made the most horsepower and torque.
(i'll see if i can find the mag somewhere...)


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

[alhope34]

I'll have to agree with Joker on the backpressure thing... Take it away and you'll have absolutely no acceleration from a dead stop at all. An engine NEEDS backpressure to work and run properly. If a 2.5" pipe was better, why wouldn't Toyota use it? A lot of people buy the Honda Fit because of its 3 extra hp. If a larger pipe was really necessary Toyota would have used it. It's because the car needs to have the backpressure there to have decent enough low RPM torque.

[largeorangefont]

I gutted my cat. and also I made my piping larger than stock. now I have a 2.5 in exhaust all the way. without the cat it's get a little bit louder. Depending if you have a straight through muffler like a N1 style. But it doesnt sound like a honda. Also your gas mileage will go down alot, Because the check engine light stays on without the cat. I actually tried both O2 simulators (mechanical and electrical) and the check engine light still comes on after a few miles. But you can feel the difference from the stock 1-3/4 inch to 2-1/2inch piping only at higher speeds. I am going to install a high flow cat to get rid of the check engine light and it should help my gas mileage a bit.

The check engine light for cat inefficiency (code (p0420) has no effect on anything. You mileage went down because your exhaust piping is too big and you lost low end power. 2.5 inch piping is too big for a 100 HP car.

[largeorangefont]

Eh, im probably not going to do it for the simple fact it will toss a CEL and kill the MPG because it cant give proper o2 readings, but acdaazn do you have a blown up picture of your sig?

The car will run fine without a cat. the front 02 sensor handles fueling, the rear checks catalyst functionality and has no influence on fueling.

[black2yaris]

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::thanks::headbang::thumbup::thumbsup::wink:: 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]

:clap::thanks::headbang::thumbup::thumbsup::wink:: 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]

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]

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]

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...:confused:

[alhope34]

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...:confused:


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

[largeorangefont]

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]

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]

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

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]

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..:wink:

[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]

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. :iono: 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]

:thumbdown: 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.:evil:

[3cyltrbo]

:thumbdown: 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.:evil:

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]

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.

[tomato]

Guys, guys, don't feed the troll.. Actually, I know what to do.

OK he's gone. Back on track, peeps.

[3cyltrbo]

Al Gore is an idiot, plain and simple.

Actually his I.Q. is about 3 x that of the last republican president (George Dubya) or any republican vice president ever........., and if I remember correctly Gore is a Harvard graduate.


For the USA to be blamed for the third worlds destruction of the earth is outright stupid.

Not even sure what to make of this (its grammatically pretty messed up) did you mean that the U.S. shouldn't be blamed for 1/3 of the worlds destruction? (because technically its the biggest consumer and the biggest polluter)

or did you mean

That the U.S. shouldn't be blamed for destruction of the earth caused by third world countries? ...................because most third world countries aren't overun with coal-fired power plants / SUV's / landfills etc...



We are made to suffer for the transgressions of others????

Really?

We drive the most efficient cars..

Really?, seriously?...........you're kidding right? (Explorers / Suburbans / Expeditions / other SUV's etc...--- not alot of those in Europe) . In most Asian and European countries, the cars that get only 30mpg are considered gas hogs, not the ones that get 15mpg like here in Americuh.

. have the most responsible laws regarding environmental protection... ..

Sorry, but have you been drinking the republican KOOL-Aid?

We are waaaaayyyyy better than ALL other countries with regards to taking care of the earth.

um, Really?????????? (actually you're probably right!............if Fox News says America is the best protector of the earth, than its 100% true)

*****cue the Team America theme song*****

"America, F**k yeah..................."

Lolz

[why?]

Actually his I.Q. is about 3 x that of the last republican president (George Dubya) or any republican vice president ever........., and if I remember correctly Gore is a Harvard graduate.




Not even sure what to make of this (its grammatically pretty messed up) did you mean that the U.S. shouldn't be blamed for 1/3 of the worlds destruction? (because technically its the biggest consumer and the biggest polluter)

or did you mean

That the U.S. shouldn't be blamed for destruction of the earth caused by third world countries? ...................because most third world countries aren't overun with coal-fired power plants / SUV's / landfills etc...





Really?



Really?, seriously?...........you're kidding right? (Explorers / Suburbans / Expeditions / other SUV's etc...--- not alot of those in Europe) . In most Asian and European countries, the cars that get only 30mpg are considered gas hogs, not the ones that get 15mpg like here in Americuh.

.

Sorry, but have you been drinking the republican KOOL-Aid?



um, Really?????????? (actually you're probably right!............if Fox News says America is the best protector of the earth, than its 100% true)

*****cue the Team America theme song*****

"America, F**k yeah..................."

Lolz

keep on lying, next time someone comes to kill you we'll let them.

None of what you said has even the least bit to do with any actual facts, it is all total rubbish. Please keep it to your socialism and slavery to the government friends.

[CrankyOldMan]

Doesn't this belong in the "open political discussion" thread instead? Something tells me this needs to be locked before it gets any uglier.

[why?]

the open political discussion group, just like all the other groups, are nonstarters and completely useless.

However this thread has swerved way off track.

removing cats totally just isn't worth it now a days. Especially when you can get race cats that are better than straight pipes.

[cali yaris]

Thoroughly entertaining. Can I throw my thread necro card?

[MadMax]

:thumbdown: 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.:evil:

What is even more hilarious is someone who owns a Grand Cherokee and thinks it is a fucking Jeep! :laughabove:

Get a REAL Jeep, that would be one that resembles the original Willys; and ditch that POS ZJ you have. It's for pussies...and I'd rather drive a Yaris than that joke! :barf:

(Damn, just noticed he's already gone! And here I am awaiting his witty response! :cry:)

[why?]

Thoroughly entertaining. Can I throw my thread necro card?

please do.

[tomato]

Doesn't this belong in the "open political discussion" thread instead? Something tells me this needs to be locked before it gets any uglier.

+1

[tomato]

going once.... going twice ....

[tomato]

hmmm... funny how it's gone quiet all of a sudden ....

[cali yaris]

Bam!

http://www.microimageonline.com/forums/images/smilies/threadnecro.gif

[tomato]

Meh, you're too late, PK. Missed all the fun :tongue:

Anyone else? or are we ready for ...




http://sclick.net/cool%20gadgets/newest-cool-innovation-gadget-ideas/04/top-coolest-best-latest-new-fun-gadgets-gifts-impossible_lock.jpg

[EPyarisdriver]

:laughabove:I have been entertained haha.. Go ahead and pull the trigger on this thread!
:laughabove:

[tomato]

Might as well! Love the Necro Card, BTW! :) Just for that, it was worth it ;) :tongue: :tongue:

OK here goes ...