Catalytic Converter, What Type?

[jcwillis]

Hi,
I checked out this Arena a while back and thought that I saw a thread on types of catalytic converters, something about two-gas and three-gas. Came back to review the thread but cannot seem to locate it.
I would like to replace the stock converter and I am in California. Car has about 170k miles on engine. Minimal mods that include an early ATR dual exhaust and ATR cone intake filter, ATR thermostat and those hot water plugoffs. Car has not been on the street for several years, but is started every now and then.
My questions would be; What type (two or three gas) of converter will I need? Are there high flow, CA smog legal converters and do they have a similar life expectancy as the stock OEM type? Approximately what am I looking at as far as cost of each (stock or a high-flow) converter? What brands are reputable or recommended?
Thanks in advance for your help.
Jim

 

[gofstbuick]

You'll want to use a three-way-cat. This cat controls HC, CO and Nox emissions. ATR sells a nice high flow unit, and you may look at our vendor list and contact one of our vendors. As far as life expectancy, nothing will last like a factory unit. The reason they are more expensive is because a factory cat uses a higher quantity of precious metals (platinum,paladium and rhodium are the catalyst used to convert emissions to less harmful gases). If you keep you engine well tuned, you should get good life expectancy out of an aftermarket cat.

 

[shmed]

is there a way to tell which one you have? i currently have a high flow type but unsure if its a 2 or a 3

 

[gofstbuick]

no real way to tell except by part number and asking the manufacturer

 

[jcwillis]

Mo' Cat Q's

Thanks GofstBuick for the info.
Shmed thank you as you pretty much asked what I was going to ask.

I discovered that finding catalytics online is easy (plenty on ebay). But getting the info whether they are two-gas or three-gas is like pulling teeth.

GofstBuick, you mentioned the ATR cat as being three-gas.
Would any other particular brand (Catco, Maremont) be more likely to build three-gas cats?
Does price ($100 vs. $35) usually indicate a three-gas cat?
Any brand/part#s you can share that are positively three-gas that fit our GN's?
Would three-gas always be the type of cat for any California vehicle?

By the way, do you work at the Cal/EPA building?

Thanks again,
Jim

 

[shmed]

hee hee, no problem..

the reason i asked was i have a cat for a terry houston pipe i got from Read A and i passed the e test last time with it but just barely..

 

[gofstbuick]

Re: Mo' Cat Q's

Originally posted by jcwillis

GofstBuick, you mentioned the ATR cat as being three-gas.
Would any other particular brand (Catco, Maremont) be more likely to build three-gas cats?
Does price ($100 vs. $35) usually indicate a three-gas cat?
Any brand/part#s you can share that are positively three-gas that fit our GN's?
Would three-gas always be the type of cat for any California vehicle?

By the way, do you work at the Cal/EPA building?

Thanks again,
Jim

Price is usually not an indication of TWC, but OBD2 TWC are more expensive than traditional TWC, though I don't know why. Since Catco and Maremont are traditional exhaust system manufacturers, I'm sure they make a very good replacement TWC. The key is to have the proper flange attached to the cat. Don't let the muffler shop weld the cat to the y-pipe, have them weld the flange to the cat and allow the cat to be slip fitted to the downpipe. This is the way the factory did it, so I would replicate it that way. I made the mistake of allowing a muffler shop to weld mine to the y-pipe. When I ordered my ATR DP, I went back to a bolt on flange and slip fit on the DP. Also, I probably bought the last exhaust bracket, so my system looks very factory. The TWC is the only cat approved for a GN in California. Especially if your vehicle requires a dyno type emissions test. The dyno is used to test for NOx emissions and the cat and EGR are the main components that control NOx.
Actually, I'm in Rancho Cordova at the Bureau of Automotive Repair HQ office.

 

[gofstbuick]

Originally posted by shmed
hee hee, no problem..

the reason i asked was i have a cat for a terry houston pipe i got from Read A and i passed the e test last time with it but just barely..

The cat supplied with the THDP is a two-way-cat (OC-oxidizing cat). Since the THDP is longer than the ATR DP, ATRs three-way-cat (TWC) will not work on a THDP. The price for the THDP (with cat) and ATR DP (with cat) was the same, but I made my choice based on the cat supplied with the DP (TWC for a ATR DP and OC for a THDP). The vendor selling the THDP said I could purchase a TWC to accompany the THDP for an additional $199, so being kind of frugal, I went with the ATR DP. If you car barely passed NOx, the TWC and the EGR system are the main components that control NOx. That may explain why you barely passed, since the cat supplied with the THDP is an OC.