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Old 02-14-2006, 09:27 AM   #1
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Good Q&A on Sport Cats.

I thought that I would share this good Q&A.

Here it is:


I see that there are a lot of sport cats being advertised for Boxsters , generally in conjunction with headers which eliminate the primary cats on the pressed manifold. Some questions: 1)Has anyone using this set-up passed a typical state emissions test? and 2)Why is it so difficult to fabricate some sort of extensiom cable for the O2 sensors? Couldn't male and female connectors from OEM bits be grafted together with appropriate wiring to do the job?


Many of the cats that are being replaced are the Main cats and not the pre-catylitic ones. Regardless of passing inspection or not Federal Law prohibits the tampering and or removal of any emissions controls, especially catalytic converters. These fines had been 300,000 per occurrence to the shop and 50,000 to the technician or person doing it. This would translate into multiplying this by the amount of cats removed. Many states will check the cats with infrared to make sure they are working.
Now after saying that would a car pass emissions with the pre-catylitic converters and main cats removed, NO. Would it pass with just the mains removed , most likely it would do to the o2 sensors are in the pre-cats, however this is still illegal. Now should they get replaced with sport cats, it may and may not pass depending on their efficiency. The pre-catylitic converters are also falsely referred to as the primary cats. These are actually a small cat that ignites off at 660F. This cat is made of a ceramic and located close to the exhaust manifold for this. The quick set off of the pollutants is done so that the larger main cats will work quicker. So basically the elimination of any catalytic converter is illegal unless for race use only and never to be used on the street.

As to the second part of your question regarding the o2 sensors is fairly simple. The first main reason is do to the added resistance in any connection. This resistance is especially critical in an o2 sensor do to its low voltage operation. The second would be that many o2 sensors sample the ambient air from the wires sheathe that are connected to them. When the wires are cut with the outer sheathe and then re-taped they cant do this properly.
Scott Slauson - PCA WebSite - 2/12/2006

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Old 02-14-2006, 10:18 AM   #2
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Join Date: Jan 2005
Location: Southern Cali
Posts: 494
He's absolutely correct.

While I was at Car Sound Inc./Magnaflow (manufacturer of OEM and Aftermarket Catalytic converters), you cannot tamper with or replace the OEM catalytic converter period. It doesn't matter if your the best aftermarket performance company. Should your OEM converter go bad, its 98% of the cats i saw they were beause of a poorly tuned/performing engine and were replaced with an OEM converter AFTER the engine was fixed.

To give everyone and idea, it would cost a couple grand for a 100 cell converter that was EFFECIENT enough for you to pass smog in California. Because of the reduced surface area, you would need to load up so much precious metals into the ceramic or metalic substrate it is just not cost effective.


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