Question About Pre-Cats

[Cristobal]

Hi All:

Does anyone know when Toyota started putting pre-cats into vehicles marketed in the USA?
My Beast was built in 1995, and I am wondering about this.
Thank you for your help.

 

[randomhero439]

All i know is, dont use a 2step with them...

 

[Lead Shoes]

Originally Posted By: randomhero439
All i know is, dont use a 2step with them...


LOL, you know first hand why you shouldn't do that huh?

 

[ccb056]

1991 Lotus Elan (Isuzu 1.6L turbo) has a precat.

I would assume a 1995 Toyota would also have one to pass emission regs on cold starts.

 

[LeakySeals]

In a recent Nissan thread I was baffled by the word "pre-cat". Toyota has a real cat welded into the exhaust manifold, nothing before it but the header and a pre-cat af/o2 sensor. Known as an exhaust "manifold cat". Official name is CONVERTER SUB-ASSY, EXHAUST MANIFOLD. Started in 02 with the Camry, 00 on the Avalon. Nothing prior to that I'm aware of.

 

[Trav]

I suppose they refer to it as a pre cat because it is in fact a cat but its too small do perform the job alone. Its primary function is to raise the exhaust gas temperature before it hits the main cat.
Because there is a conversion process taking place so it also allows the manufacturer to use a smaller main cat to save space.

The term seems to be a Nissan thing though.

Here is a good article about "Pre Cats"

http://www.toyotaownersclub.com/forums/index.php?showtopic=70844

 

[Donald]

Not sure about pre-cats, but I have an orange cat that needs a home.

 

[Cristobal]

One of the reasons I am maintaining the Beast is that I do not want to buy a new car and have to monkey with too much of this nonsense.

It will need a new cat possibly at the end of 2013 to pass the smog test, but I have found a muffler shop that has incredible deals.

 

[LeakySeals]

If your consuming oil, thats where you start. Consumption is the main cause of cat death. Aftermaret cats are hit or miss. Not enough/less catalyst media (why they are cheaper than OE), you could illuminate a P0420 catalyst efficiency CEL. But I think in your year the ECU threshold for that light was lower, so aftermarket "should" be ok.

 

[steveh]

Originally Posted By: Donald
Not sure about pre-cats, but I have an orange cat that needs a home.
Maybe KevGuy would like a orange cat!!

 

[Phishin]

For me, any many others I talk with in person, and on other forums.....

Pre-cat is the oxygen sensor before the cat.
Post-cat is the oxygen sensor after the cat.

Never heard of a cat to raise exhaust temps, but not really function.

perhaps you guys are talking about resonators....??

 

[Rand]

its the mini-cat thats near the engine that works in conjuction with a larger one farther along.

some cars have as many as 3-5 total assemblies.

 

[Cristobal]

It consumes no significant oil. It had an oxygen sensor fail once or twice, and the it passed smog testing a year ago, but barely.

 

[Trav]

Did you read the article? Post cat O2 is just a cat monitor. All OBD II systems will have an O2 or AF monitor and a post O2 regardless if a pre cat is used or not.
I have never seen a resonator before the cat or pre cat.

 

[PandaBear]

My understanding is the pre-cat is used in California emission vehicles that couldn't meet requirement with only the main cat.

 

[artificialist]

It really depends on the model. Some Toyotas needed more exhaust aftertreatment systems than others to pass smog tests