canzoomer

To some degree.
I have doubts about those claims.

If you add more air flow to a stock ECU tune it responds with more fuel. That is about thelast thing we want!

Japan8

Understanable academically, especially when combine with your tuning experience with the 8. RB also said something similar at first, however, I seem to recall them singing another tune as work really got underway in that direction.

"Intake - We have spent considerable time and effort in evaluating the stock intake system on the RX-8. Although we held some early reservations that a simple "open element filter" intake configuration would produce additional power, our initial testing has shown some promise with this type of intake. But, one negative aspect of this configuration is the extremely loud intake sound that they can produce. Our first experience with one of these aftermarket systems produced an ear-piercing +90db reading (at the driver's seat) at approximately 6000-7000 RPM!"

I am figuring that they are refering to the gain K&N system or something similar as reports here have been that it is LOUD.

What I'd like to see are dyno figures from a car with the RE intake, CZ Stage 1, high temp/flow cat and a cat back exhaust. I'd like to compare those figures to CZ's Stage 1 figures on a stock car...

Rotarian_SC

Canzoomer, i have a question regarding the cat for stage 1, since it wears out early and we don't know how early, how can we tell when it has worn out. I am sure we all love our rx8's but i doubt nebody who has ur kit has 50k miles on their car yet, which is what i believe what the old CA law was for. I was just wondering so i don't damage my engine. Sorry if this has been asked i just read this whole post in one sitting and that's a lot of data.

Lock & Load

Stage 1 will not have any effect on the stock exhaust system and cat .
Its only in stage 2 that the temperatures are higher in the exhaust that the stock exhaust and cat can handle thats when you need to change the exhaust .
michael

canzoomer

OK, here is what will likely happen:
We believe the original design and tuning was for a car that had to meet the old regulations that required the catalytic converter to last at least 50,000 miles.
The new EPA2 regulations require the cats to last 120,000 miles.

Mazda re-tuned the cars and made the fuel mixture much richer at higher rpm range.

In comparison between a tune that is stock versus one with the added power levels in Stage1 we saw the exhaust gas temperatures at a peak of 1610F in stock and 1650F with our tune.

Any amount of higher temps will diminish the cat life to some degree. How much can only be told over time, as you allude to above. It will not be likely to make a big difference until you get to around 1750F or higher. We see this kind of a temperature with a more extreme tuning level, with much leaner mixtures.
In our Stage2 map that we wille shipping, we see EGT's up to 1800F peak, and 1760f sustained at high rpm, wide open throttle runs.

That will certainly damage a cat as it will strip the coatings off the catalytic converter elements.

So, to recap:
Stage 1, possibly slightly diminished life.
Stage 2: Remove the stock cat, or kill it.

None of this will risk damaging your engine, or anything else, except the cat in the more extreme tuning parameters.

It is a possibility that the stock cat will not last as long with Stage1 compared to stock.

Let's do some math here.
The current fuel consumption is averaging about 16mpg for the more spirited drivers here.
The Stage1 tune will likely save you about 1mpg in this case.
Let's say you do 12,000 to 15,000 miles per year.
That is about 8-10 years for 120,00 miles.

At 16mpg you will burn about 938 galons of gas a year.
With stage 1 you will save about 55 gallons a year.
At $1.50 to $2.00 a gallon that adds up to about $85 to $110 a year.
Over 5 years that is about $425 to $550 of gas savings.
A new cat from Mazda costs about $1,100
So, if we shorten cat life by half ( 9 years down to 4.5 years) it will cost you about an extra $550 to $675 in replacement cat at 4.5 years.
About $125 a year for 4.5 years use.

That is about the worst case scenario.

RX-Nut

I know this way premature in asking but.... How can you tell if your cat has gone bad?

QuantumTheory08

....you may see he or she wearing more leather products.

There may be a nicotine stain on the paw and a new, different crowd your cat hangs around with; be aware of these suttle hints in changed behavior.
:p

......I think in most cases, the cat stops doing it's job in removing nitrogen-oxygen and carbon-oxygen radicals from it's exhaust (they show up on a smog check). Extreme cases are: it melts and is rattling around in there or increased back pressure (decreased performance output).
:D :D :D

adrian-1

Wouldn't the o2 sensor detect it and throw a check engine light?

canzoomer

You can not without instrumentation.

The ways it can be diagnosed are:

1) Failure to function. If you go for an emissions test and it fails.

2) Exhaust CO levels are too high. The O2 sensors before and after the cat may cause a fault condition, showing up on the dash as a "check engine". This is less precise, as I have seen cases where people removed the cat and did NOT get the check engine in some cars.
Still, in theory it should happen.

3) By measuring exhaust gas temperatures before and after it.
The cat uses some residual fuel in the exhaust gases to "power" it's process. As a result the temperature after thecat is typically 30F to 50F hotter after the cat.



That is how we monitor a cat for testing.
Insert two threaded bungs, before and after the cat.
Insert pyrometer probes into the bungs.
Hook these up to gauges, warm up the car and drive it.
Observe the EGT's

canzoomer

That's true.

loco4rx8

So, does a failed cat cause no problems with the car, other than a failed emissions test? In other words, could one drive around forever (until they have to have an emissions test) with a bad cat and not know it with no ill effects to the car?

ranger4277

Yep. A cat is purely for emissions. I think it is possible for it mess up your exhaust flow.. I'd like to hear if it is true. When the crap blows out the back of the cat can't that cause some restriction in the system? I've heard stories of cats being overheated and glowing particles coming out of the exhaust pipes.

RX-8 friend

Older design cats. would plug up when they failed. That could harm the engine, but anyone who has experienced it would tell you those who damaged their engines from this are idiots. Reason is you get a huge loss of power. If you notice this and do nothing, then you are an idiot, by definition .

Hmmm, glowing particles, and from other threads, flames. I guess the RX-8 is not USFS approved.

QuantumTheory08

....I'm still sticking to "watching" cat behavior and nicotine stains as early signs of trouble.

zoom44

i watched a girlfreind's mother's car burn down to nothing from a pluged up and overheated cat., about 5 minutes after i helped carry groceries from the car into the house. it started when the cat got so hot that the interior carpet lit up and there went the whole car.

RX-jimenez

is too early to be worrie about that right????

MPG > HP

Has anyone ever tried or marketed a pre-cat pipe that had cooling fins or hundreds of cooling "spikes" designed to reduce exhaust temps to non-damaging levels? The fins or spikes would probably need to be asymmetric to conform to space restrictions and air flow characteristics and possibly have to intrude into the exhaust flow to be effective. Such a device would be costly but perhaps would allow us unwashed masses to install a Stage 2 or extend cat life with a Stage 1, making for some cost recovery.

canzoomer

The problem with cooling the exhaust is difficult to accomplish.

Here's why:

A catalytic converter requires the exhaust gases to be at a specific minimum temperature for it to work. Around 1200F to 1625F

Below that it does not work. This is why there is warm-up time before an emissions test.
With the new EPA2 spec for testing that warmup time is 5 minutes or less.

If you add cooling, to reduce maximum temperatures for WOT runs, then you cool the exhaust down too much for normal driving, and the cat will not work.

One possible method of coolig exhaust to correct temps is to use water injection the the header. When the temps reach a certain level it injects water in a mist.
This is a complicated and expensive procedure.
You need:
Water reservoir.
Injection pump.
Piping.
Pyrometers to measure temps.
Electronic selenoids to turn it on and off.
A control device with logic to manage it all.

A pretty complex and expensive proposition.

And there are down sides, such as the water causing corrosion in the exhaust system.
If you run out of water you can ruin your cat.

In general, if you run a tune level that creates high exhaust temps, you have no chance of meeting emissions specs.

Modern cats will not plug and overheat like some of the older designs, so if you do cause a cat failure, it will not melt the catalyst bricks and cause a fire, or plug the exhaust. It will simply stop working. And that is a $1,200 repair to replace the cat.

OTOH, the cat is in a bolt-in midpipe in the RX-8, so prepping for a test is easy.

If you live in a jursidiction that does on-road spot check inspections, however this will not help you.

California , for example..

Genom

Florida though, is a whole different kettle of fish :D

neit_jnf

How about taking the stock midpipe with cat and remove everything inside then reinstall the empty shell?

93rdcurrent

Destroying and emptying the cat has been done but what you guys should keep in mind is that tampering with emissions equipment in such a manner has serious consequences in states or countys where emissions are enforced. So don't get caught. I prefer to go with a high flow and high temp cat. If you go this route make sure that you run your engine to atleast 4500 rpms for 5 min before an emissions test. Don't wait in line for 45 min and just go up and do your run. Pay attention to the person ahead of you and get your car up to temp before making your run for emissions. If your cat doesn't get up to temp it won't work.

JimW

Good point 93rdcurrent, Plus I don't think your going to loose that much power having a high flow cat vrs a staight pipe or hollowed out cat (meow). In any case it's definitely not worth getting caught and in having one, while it still might not pass EPA standards, your still preventing some harmful material from damaging the environment!

canzoomer

That is one expensive shell!
Jurisdictions that do spot checks also require real tests at least annually..

Now if you could find on at a wreckers..

canzoomer

Darned right.
Laws say $2,500 fine to the individual caught tampering, and $25,000 to a shop caught doing it!

Ouch!!

Oh, yeah, it's a FEDERAL LAW!

AndyPearce

Canzoomer - how do you mark up packages for shipping to the UK? I need to know so I can work out import tax / VAT payable on entry etc.

They work the import duty based on the type of item being imported and then the VAT is based on (item price + shipping + import duty) x 17.5% (Ouch!)