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Discussion Starter #1 (Edited)
If you live in an area that does advanced smog testing.. don't waste your money on a catted downpipe.

I bought a catted downpipe a few years back, and had to go this month for my emissions testing.

At Advanced Smog Testing Facilities they test HC (Hydrocarbons) CO2 (Carbon Dioxide) and NOx (Nitrogen Oxide)

My Catted Downpipe allowed me to pass HC and CO2. But I failed NOx miserably!!

Here's the important part:
I spoke with the state emissions inspector (very nice guy btw) and he advised me that on WRXs... we have 2 cats in the downpipe because we don't have an EGR system. The two cats are used to break down the NOx. One cat would be sufficient to break down the HC and CO2 (just as mine was). But only our stock exhaust is able to break down the NOx.

I asked him how to reduce NOx levels without putting a stock exhaust back on. He said that NOx is produced by high EGTs (exhaust gas temperatures). Our turbo charged cars run a higher EGT than the standard car (1400degrees is common).

The only ways to decrease NOx are with alcohol/water injection, an alcohol fuel source (E85) or increasing the fuel / retarding the timing.

Retarding timing / increasing fuel would allow less fuel to be burned increasing the HC output. Alcohol / Water injection would lower the NOx level, but not enough. E85 would also lower the NOx level... but not down to levels acceptable for a 4cyl car.

Solution? Stock downpipe for emissions testing. And Catless for stage 2+
 

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Discussion Starter #3
You will pass on e85. People have passed catless on it.

Sent from my DROIDX using Tapatalk
passed NOx? and where?
 

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You will pass on e85. People have passed catless on it.

Sent from my DROIDX using Tapatalk
I think his point is that cat vs catless: the price difference isn't worthwhile, if you're only doing it to try and pass emissions..


That's what I got from reading it. Is that correct, Kevin?



Oh, and welcome to the forum, Tohsh.
 

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Discussion Starter #6
I think his point is that cat vs catless: the price difference isn't worthwhile, if you're only doing it to try and pass emissions..

That's what I got from reading it. Is that correct, Kevin?
Exactly what I was going for.
 

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Discussion Starter #7
California. All I know is we have strict smog regulations but can't recall if they test nox.
In california they do test NOx, but they test you at 15 and 25mph.

In Colorado we have a full dyno test that is variable, and includes acceleration under load on the dyno. They accelerate several times up to 60 mph during this test which takes up to 5 minutes.

The state inspector advised me that he has had several modified vehicles still fail NOx while tuned for E85.
 

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http://www.aa1car.com/library/tr1196.htm
Most vehicles that are in good running condition and properly maintained should pass an emissions test. In some cases, though, minor problems may cause the vehicle to fail an emissions test. These include:

* Engine and/or converter not at operating temperature. If a vehicle is only driven a short distance to the test facility, it may not be warm enough for the engine to be at normal operating temperature and/or the converter at light-off temperature. This will affect the emissions of the engine and may cause it to fail. Excessive idling while waiting in a test lane may also cause the catalytic converter and/or oxygen sensor to cool down enough where they may not control emissions properly causing higher than normal readings.
* Idle speed too high. A few hundred rpm can sometimes make the difference between passing and failing an emissions test if emissions are marginal.
* Dirty air filter. A restricted air filter will choke off the engines air supply, causing higher than normal CO readings.
* Worn or dirty spark plugs. Excessive plug gap and fouling deposits can create ignition misfire resulting in excessive HC emissions.
* Dirty oil. The oil in the crankcase can become badly contaminated with gasoline if a vehicle has been subject to a lot of short trip driving, especially during cold weather. These vapors can siphon back through the PCV system and cause elevated CO readings.
* Pattern failures. Some vehicles tend to be dirtier than others for a given model year because that is the way they were built. It may be the design of the engine, or the calibration of the fuel or engine control system. These kinds of problems may require special "fixes" that can only be found in factory technical service bulletins.

In areas that have plug-in OBD II emissions testing for 1996 and newer vehicles, the vehicle will be rejected for testing if all of the required OBD II readiness monitors have not run. This may require driving the vehicle for several days until all the monitors have run. The vehicle will also fail the test if (1) the test computer cannot establish communication with the vehicle PCM (defective or disabled diagnostic connector), (2) if the Malfunction Indicator Lamp (MIL) is on, or there are fault codes in the PCM. If the OBD II system is working properly, the MIL is not on and there are no codes, the vehicle should pass the test.

to pass, you need this combined part: a catted muffler..

 

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California. All I know is we have strict smog regulations but can't recall if they test nox.
How would a catless car pass emissions in CA, given the visual test?...
 

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Discussion Starter #11
How would a catless car pass emissions in CA, given the visual test?...
Great point. Tohsh's point can't be legitimate.
 

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Discussion Starter #12
Thanks to he who stickied.
 

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False/gutted piping. If the tech isn't thorough enough, an empty catalyst chamber or welded heat shield could be enough to fool him.
not trying to be too picky, here, but I think the reference is "buying" a catless up-pipe, not hollowing the stocker.
But I totally see what you're saying.
 

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One thing to think about when going catless, besides the environmental impact, which is obvious, is that it is against federal EPA regulation to knowingly remove the catalytic converters from a vehicle. I believe the fine is up to $50k now for a service center that removes it and $15k for the owner of the vehicle. For me, that's enough to go catted.
 

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One thing to think about when going catless, besides the environmental impact, which is obvious, is that it is against federal EPA regulation to knowingly remove the catalytic converters from a vehicle. I believe the fine is up to $50k now for a service center that removes it and $15k for the owner of the vehicle. For me, that's enough to go catted.
and you can still make big power with a cat. converter; all my previous build (minus the diesels) have been catted. Albeit larger 3" or so, but at least they were still cat-equipped.
 

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jd92677 said:
One thing to think about when going catless, besides the environmental impact, which is obvious, is that it is against federal EPA regulation to knowingly remove the catalytic converters from a vehicle. I believe the fine is up to $50k now for a service center that removes it and $15k for the owner of the vehicle. For me, that's enough to go catted.
You're still tampering with emission control devices and breaking that same statute ;)
 

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You're still tampering with emission control devices and breaking that same statute ;)
True... I have stock exhaust on my car and plan on keeping it that way (I'm more interested in the environmental impact than the fine). But given a choice, at least have a cat on there.
 

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it's kinda like running off-road diesel. "if you get caught, it's like $1K-5K gal. on the first offense. some have been dealt a $10K fine first time..


Ouch..
 

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