Does anyone know of any companies that are working on or have completed a cat-less exhaust system?

isnt that illegal

Anything that removes or alters the emissions control systems in any way has to marketed as a "race only" or "off road use only" system. In the state of Texas it is actually illegal to remove your own emissions systems although no one enforces this law. Many people think that it is only illegal for a shop to remove them. Remember that the RX-8 is very computer controlled. The car also has 2 O2 sensors. One before and one after the cat. It compares both signals and tells the computer if something is wrong or not. Who knows what kind of signal the computer will receive if you remove the cat. The Camaro's have a part available called an O2 simulator which plugs in where the rear O2 sensor was (before the cats were removed if they were) which sends a false signal to the computer so there is no error code. Maybe we need one for the RX-8 as well. It is just a resistor. The question is, does the computer go off of any reading in a range or does it constantly correct for different ones?

Originally posted by rotarygod
Anything that removes or alters the emissions control systems in any way has to marketed as a "race only" or "off road use only" system. In the state of Texas it is actually illegal to remove your own emissions systems although no one enforces this law. Many people think that it is only illegal for a shop to remove them. Remember that the RX-8 is very computer controlled. The car also has 2 O2 sensors. One before and one after the cat. It compares both signals and tells the computer if something is wrong or not. Who knows what kind of signal the computer will receive if you remove the cat. The Camaro's have a part available called an O2 simulator which plugs in where the rear O2 sensor was (before the cats were removed if they were) which sends a false signal to the computer so there is no error code. Maybe we need one for the RX-8 as well. It is just a resistor. The question is, does the computer go off of any reading in a range or does it constantly correct for different ones? \

Yes, I know its not street legal and I'm pretty sure the check engine light will come on at random times while im driving, but there are ways I'm sure to trick the O2 sensors like you mentioned with the camaro. Any info on how to go about it would be appreciated.

SR Motorsports said that have released a "mid pipe" at the sevenstock event. They said they had got 11 hp gain on the dyno and also picked up some torque. They are also going to work on
a free flow cat system. They said the "mid pipe" was released the
week before.

i am thinking of removing my cat tomorrow night...just for the night to see what it sounds/runs like.....if it runs! i was wondering on top end i think it is going to sound more beastly wouldnt you think?


andrew

In Florida it is not illegal to remove your cat from your car. I actually know a lot of people who have done it etc. I hear HP gains of almost 10HP when removed from most car's. I am looking into a non-cat back as well. I just don't want to mess around with screwing up the computer. That's why I think I'm going to wait until at least the new year before I start moding my 8. Just seem's like more info will be out by then.

Originally posted by mikeb
isnt that illegal

haha mike i dont know why i find that quote funny.....but i think its freaking hilarious!, i think its just the tone...haha just had to say that


andrew

I was wondering what it would take to replace the cat in the 8 with a straight pipe that has an o2 simulator installed...i've heard some people mention multiple cats...oil injectors....can someone give me a description of the setup and what I'd have to do to get around it? any predictions on performance gains would be great also. thanks.

A complete disregard for both the law and the environment, for a start.

Originally posted by eccles
A complete disregard for both the law and the environment, for a start.

Nothing like a knee-jerk, petitio principii argument to answer someone's question. You assume an awful lot with an answer like that and it puts you way out of your depth.

I'd suggest a real O2 sensor rather than just a simulator.
I haven't gotten my hands around that part of an RX-8 yet, but I suspect the gains would be minimal without the requisite fuel re-mapping.
Without the O2 sensors you would just have a crappy running car.

Ecc are u a treehugger?

Originally posted by WTF no turbo
Ecc are u a treehugger? Not at all. Lord knows I used to have an abundance of disdain for EPA requirements in my youth, but these days I do tend to see the bigger picture. I'm far from being a greenie, but I do acknowledge that the rules are there for a reason.

If the car is going to be used for track work only, then go for it. But if it's going to be used on the road every day, and thus contribute to pollution which will result in both lesser quality of life and more stringent emission requirements for every other law-abiding driver, then yes, I have a problem with it.

I'm with you on that issue eccles. I think it's absolutely frightening how people remove their cats (or worse gut them) for just regular everyday driving without a single though about the consequences.

Both of my Mazdas pass the fairly stringent Maryland emissions tests without any catalytic converters at all (just a catalytic-shaped "test" pipe.
Tuning is far more important than a catalyst. The cat was designed to make up for the slothful habits of the average vehicle owner.

However, with the advancements in Cats, the resistance across them is so minimal, the gain's, at least in my opinion, aren't really worth the extra pollution. What would be better (at least in my opinion) is just to have a complete new system made from header back, using some larger cats, which will produce less pressure drop, and give more power, without wrecking air quality.

Originally posted by Maniac
Both of my Mazdas pass the fairly stringent Maryland emissions tests without any catalytic converters at all (just a catalytic-shaped "test" pipe.

Neither of your mazdas are rotaries, which barely pass emmisions as it is.

If you're driving in traffic, it doesn't matter if you have slothful habits or not. And guess what, those areas that have lots of traffic are exactly where you would want stricter emissions laws. And how are cats making "up for the slothful habits of the average vehicle owner"? What are you talking about?

I know that replacing the cat with a test pipe would be very cheap, but I still say that it's still not worth it. I wouldn't want my $30k car spouting the poisonous fumes of a American car from the 70s.

Originally posted by CraziFuzzy
However, with the advancements in Cats, the resistance across them is so minimal, the gain's, at least in my opinion, aren't really worth the extra pollution. What would be better (at least in my opinion) is just to have a complete new system made from header back, using some larger cats, which will produce less pressure drop, and give more power, without wrecking air quality.


Do larger or "high-flow" cats work as effectively as their stock counterparts in controlling emissions?

Most do, the way a cat works is that when at high temperatures, the gases in contact with the catalyst (a combination of Platinum and Palladium) cause many harmful compounds to be converted to not so harmful compounds. Specifically:

Carbon monoxide changes into carbon dioxide.
Nitrogen oxides change back into nitrogen and oxygen.
Hydrocarbons change into carbon dioxide and water.

The effectiveness of a catalytic converter is controlled by two things.

1. It has to be hot enough to cause all three reactions to occur
2. It has to have contact for long enough with a majority of the gasses. This is why they are usually a honeycomb, so that the gasess are never far from the catalyst.

Most high flow cats are physically larger, so that with the same size honeycomb cells, but more of them, the gasses are just as close to the catalyst, but since there are more holes, there is less restriction.

Originally posted by CraziFuzzy
Most do, the way a cat works is that when at high temperatures, the gases in contact with the catalyst (a combination of Platinum and Palladium) cause many harmful compounds to be converted to not so harmful compounds. Specifically:

Carbon monoxide changes into carbon dioxide.
Nitrogen oxides change back into nitrogen and oxygen.
Hydrocarbons change into carbon dioxide and water.

The effectiveness of a catalytic converter is controlled by two things.

1. It has to be hot enough to cause all three reactions to occur
2. It has to have contact for long enough with a majority of the gasses. This is why they are usually a honeycomb, so that the gasess are never far from the catalyst.

Most high flow cats are physically larger, so that with the same size honeycomb cells, but more of them, the gasses are just as close to the catalyst, but since there are more holes, there is less restriction.

Thanks for information, it was very helpful.

Maniac where in maryland are ya?

Originally posted by WTF no turbo
Maniac where in maryland are ya?

Generally just in front of the big cloud of poisonous gases ;)

Originally posted by JohnnyCumLately
Generally just in front of the big cloud of poisonous gases ;)

I've been to Birmingham and the air there is hardly clean. By comparison, it is crystal clear here - we don't have "ozone alerts" or other breathing issues, even in the summer.
So get stuffed JohnnyCumQuickly. ;)

I'm really surprised to see how reactionist, left-leaning and illogical some members of this group are.

If every privately owned motor vehicle in the US suddenly had no catalytic converter, the increased smog output would still be less than half of what is put in the air by total output of commercial vehicles today that are NOT under the same restrictions because of effective congressional lobbying.
Commercial vehicle traffic - trucks, busses, trains and aircraft - produce nearly 90% of the total pollutant content in the air over North American urban areas and they are almost completely unregulated.
Take all of the pollution ejected into the air by human beings in one year and it still accounts for less than 10% of polluting content present - mother nature is the biggest polluter of all.

I'm in Gaithersburg. Feel free to come breathe the air....

Originally posted by Maniac
I've been to Birmingham and the air there is hardly clean. By comparison, it is crystal clear here - we don't have "ozone alerts" or other breathing issues, even in the summer.


Keep in mind that one of the important factors affecting air quality is the weather system and topology in the area. This is why the LA basin is so bad. There are planty of areas where more pollutants are created and put in the air, but because of the way the air passes through the area, it makes a world of difference. However, poluutants are pollutants, and while they may not be building up in your area, odds are any extra pollutants produced there are building up where the winds trap them... like the LA Basin, and, I'm guessing, Birmingham.

And don't forget about "grandfathered" industries. ie, congress has specifically exempted certain industries from having to upgrade their pollution controls until 2020 or something like that. Don't get me wrong, I'm very much pro-business, I'm just saying let's consider all the factors. Meanwhile, the EPA pushes cars to go from producing .0001% pollution to producing .0000001% pollution, which is not a very cost-effective way to clean the air.

Heh. You guys want ridiculous pollution? Try Mexico City. It's a valley surrounded by mountains about 2200 meters up. When I left 6 years ago all cars could NOT drive at least 1 day a week, and during elevated pollution (especially during winter) this was set to 3 days a week (2 weekdays and 1 weekend day). This was normal for about the previous 6-7 years. Everyday the pollution levels are unacceptable by international standards, creeping into dangerous about 60% of the time, and very dangerous about 15%, meaning schools closed, work suspended and car usage restricted.

And like in most other places, they curtail the private sector. But the public buses spew so much crap into the air you cant breathe near one, and the northern edge of the entire city is dedicated to factories that if they where relocated 30 miles north, on the OTHER side of the mountains, would cut pollution levels by 80%.

And have they? OF COURSE NOT. The .2% of the population that controls most of the money might be inconvenienced a bit by this and so the polititians do nothing about it.

Yeah, Mexico City is a craphole. You can say it. I sure know it. But most other places are cool.

Has anyone thought about the fact that the car is an OBDII computer and removing/gutting the cat without modifying the signal from the second o2 sensor will trip the CEL and even if it's cleared it will show up again almost immeadeatly(sp)?

Originally posted by Barnstormer
Has anyone thought about the fact that the car is an OBDII computer and removing/gutting the cat without modifying the signal from the second o2 sensor will trip the CEL and even if it's cleared it will show up again almost immeadeatly(sp)?

Yeah, that's why in his original post, he stated that he wanted to install a dummy sensor...

Yes, I too was wondering what would happen if the second O2 sensor was not 'happy'......surely the computer wants to see some difference between sensors #1 & #2 ?

I am also concerned about the logic of tuning the engine so that it meets some upcoming federal standards, by riching out the mixture so that you use a tankful in 200 miles instead of 300....
Where is the greenhouse gas sensitivity in THAT?

The kicker is that some Euro countries tax the car on how much CO2 it puts out, so the tuning for the catalyst not only uses more fuel and costs more cash, it actually puts the car into a higher 'tax' bracket! Go figure.....
.
.
.
doc

If you tie the second O2 sensor input to the first sensor with a potentiometer, you can tune the relationship to the ECU's satisfaction.
That is how I did it on my Miata.

The EU monitors the cat by the use of 2 O2 sensors.
It expects a difference of levels.

O2 sensors typically output a DC voltage, whcih varies depending on reading.
If the cat is doing it's job properly it will convert CO t CO2, yielding a lower oxygen level after the cat than before. The O2 sensor monitoring allows theECU to tell if the cat is doing it's job properly. If you remove the cat, then the difference in readings will not be there and a ECU code will result.

The method of simulating that the cat is still there that is most effective is a simple logic device that reads the first O2 sensor, and produces an adjusted voltage controlled by this for the second O2 sensor input to the ECU.

It is quite feasible to make a midpipe with a higher flow cat that can take higher exhast temperatures, allowing for leaner mixtures and more ignition advance.
This does raise the exhaust temps, resulting in the need for a more robust cat.

However, such a setup will NOT pass the emissions requirements in some states, notable California.

It is quite feasible to make a midpipe with a higher flow cat that can take higher exhast temperatures, allowing for leaner mixtures and more ignition advance.

Based upon your wording, am I to assume one does not exist yet? Will it need to made specific to the RX-8 to satisfy a specific configuration?

Remember that the current cat is wedged in there pretty well (note the lump in the floor on the passenger's side. A high flow unit if it is bigger is going to cost you some ground clearance.

Canzoomer,

Would even a high flow unit not pass Cali? or where you refering to using a straightpipe?

For racing apps where you wanted to remove the cat, a simple voltage devider would work well to reduce the signal coming out of the second O2 sensor. You could mount the O2 sensor in the straight pipe replacement and with a couple resistors reduce the signal going to the ECU. I don't think you need a seperate logic circuit.

You could also just simply ground the connection and not use an O2 sensor, but that might be too clean as far as the ECU is concerned.

-Mr. Wigggles

In California you have to pass a visual test as well... they physically check if the cat under yur car is the cat it left the dealership with.:mad:

Originally posted by rxeightr
Based upon your wording, am I to assume one does not exist yet? Will it need to made specific to the RX-8 to satisfy a specific configuration?
The converters exist.
We have to implement them in mid pipes and test them to verify they work properly in this application and survive.
To monitor function we have to add sensors for temperature after the cat, and then run it for a month or so to verify it survives under hard use.
This is not going to be an overnight process.
Who wants to get a high-flow cat, only to find out it fails in a month?

I am sure there may be others working on this too.
We are about to build a couple for testing, and Random Tech in Atlanta want to build one as well.

If you are in the area of Atlanta Georgia, and would like to be a guinea pig, email me off-list and i will hook you up with Random.

Speaking of Random Technologies, Canzoomer, have they had any luck with developing a high-temperature cat yet? I'd love to find one that would survive your Stage 2 mod.... :D

Originally posted by MrWigggles
Remember that the current cat is wedged in there pretty well (note the lump in the floor on the passenger's side. A high flow unit if it is bigger is going to cost you some ground clearance.

The stock cat is kind of poorly implemented in the RX-8. It is mounted and shielded in a rather kludgy way.

You can just see it was not the one they originally designed for.
It is the lowest point by far on a stock RX-8 already.
Our design will not stick out any further, and one of the design goals is for it to stick out less, so it is not the obvious damage point if you bottom out.
I personally think that by makiong the cat stick out in this fashion is awful design by Mazda. Having a $1,800 item as the low point is a design disaster!

Canzoomer,

Would even a high flow unit not pass Cali? or where you refering to using a straightpipe?

I doubt that anything other than the stock, or similar to it , will pass in California. Personally I find it ludicrous that doing this makes your car illegal in California, but you can legally purchase a diesel pickup that make 8 times the pollution as the RX-8.
But then i live in Canada, not California, and we have our own share of legislative idiots up here too..


For racing apps where you wanted to remove the cat, a simple voltage devider would work well to reduce the signal coming out of the second O2 sensor. You could mount the O2 sensor in the straight pipe replacement and with a couple resistors reduce the signal going to the ECU. I don't think you need a seperate logic circuit.

That is essentially wehat I meant. You also want to add a diode and an opto-isolator to prevent feedback and noise, and to reduce the chance of damage from a high voltage spike feeding back from static and frying the ECU.


You could also just simply ground the connection and not use an O2 sensor, but that might be too clean as far as the ECU is concerned.

It is. I tried it already. It gets unhappy after about 15 minutes on the road and throws a check engine.


-Mr. Wigggles

Originally posted by Omicron
Speaking of Random Technologies, Canzoomer, have they had any luck with developing a high-temperature cat yet? I'd love to find one that would survive your Stage 2 mod.... :D

Dave from Random has sent me two cats to test in my prototype midpipe designs.
Once I have some mileage on them I will know more.

We are going to be running two cars with two different setups using these.

Random makes a couple of units good to 2000F+, which is a lot higher than the stock one that can take about 1,750F.

However these take a LOT longer to heat up to full operating temperature, so will never pass the new 5 minute warmup used in Califonia.

Here is a source of interesting reading materials on Catalytic converters and regulations:

http://www.epa.gov/otaq/cert.htm

Of special interest is this spec set:
http://www.epa.gov/otaq/stds-ld.htm

And here is what goes in to effect for 2004.
This is the new Tier2 emissions schedule, which Mazda had to meet with the RX-8 release.

http://www.epa.gov/oms/tr2home.htm

Perhaps most importantly, if you consider using an aftermarket exhaust on the road, there is a federal law that governs this.
I suggest that you read and become familiar with THIS DOCUMENT.

It quite clearly expains the law.
It also clearly explains a LTO about catalytic converters in layman's terms.


http://www.epa.gov/otaq/cert/factshts/catcvrts.pdf

Originally posted by canzoomer
DRandom makes a couple of units good to 2000F+, which is a lot higher than the stock one that can take about 1,750F.

Now that's really encouraging! 2000F+ might just survive your Stage 2 mod..

Originally posted by canzoomer
However these take a LOT longer to heat up to full operating temperature, so will never pass the new 5 minute warmup used in Califonia.
I'm not in CA, so I don't have to worry about the same requirements they do. :D

Originally posted by Omicron
Now that's really encouraging! 2000F+ might just survive your Stage 2 mod..


I'm not in CA, so I don't have to worry about the same requirements they do. :D

We think it will, but have to do some testing first.

One cautionary note about the emissions, as of now 2004 model year cars come under the new EPA regulations for catalytic converters and emissions.

I really suggest reading this:
http://www.epa.gov/oms/tr2home.htm

The EPA OTAQ (Office of Transportation Air Quality) website has a tremendous amount of information and it is one of the main sites where I have done a fair bit of reading in the last few months.

Unfortunately, there is so much information there that not too many people will end up reading much of it.

I've tried to summarize some of the information in the below thread:

http://www.rx8club.com/showthread.php?s=&threadid=1341

Hopefully it will be helpful to some people.

Brian

Originally posted by Maniac
If you tie the second O2 sensor input to the first sensor with a potentiometer, you can tune the relationship to the ECU's satisfaction.
That is how I did it on my Miata.

And tons of other vehicles.... Some just leave the 2nd Cat monitoring o2 in the vehicle with the resistor circuit which mimics having that cat. All you gotta do is monitor the output of the 2nd o2 sensor, with and without the cat, and select the appropriate resistor.

When going for emissions tests, just reinstall the original cat that you saved in storage for this purpose.