Posted to Technical Theory Forum on 1/20/2009
Aftermarket Catalyst Terminology
Given the recent law changes in California and the posts, I
thought it might clear up some of the confusion (or at least
not add more to it) to explain some of the terms commonly
used with aftermarket cats so it makes a bit more sense.
There are some that are quasi-legal terms that are used by
the cat regulations and then there are many that are
marketing/advertising terms used by the cat manufacturers.
'CARB-approved' -- Should mean that the manufacturer has
applied for and received and Executive Order (EO) number
from CARB certifying that the specific catalyst model has
meant the minimum criteria and been approved by CARB. The
proof is an EO #. If it has an EO #, it has been approved.
If not, it has not.
EO number -- Executive Order number. Just like other
aftermarket emission controls that are not identical to the
OEM part (replacement parts) such as intake kits, headers,
add-on superchargers, etc, if the part has gone through the
legal process to be approved for use in Calif, it gets an EO
#. There is actually a document on-line for each EO # that
describes the part, the testing that was done to confirm it
was legal, and in the case of aftermarket catalysts, all the
vehicle applications that the specific part is legal for.
'EPA-approved'/'Federal-approved' -- A marketing term, not a
legal term. It means nothing because EPA does not have an
approval process whereby they review and approve catalysts.
To be legal for sale Federally, there are rules but it is up
to the catalyst manufacturer itself to decide their cats
meet the rules and thus, are legal. There is no application
submitted to EPA nor does anybody review it or issue an
approval or anything like that.
'49-state legal'/ 'OBD
II-legal'/'OBD-legal'/'OBD-compatible' -- More marketing
terms. Again, outside of California, it is up to the
catalyst manufacturer itself to decide if its own cats meet
the Federal rules or not. The Federal requirements are quite
simple--the catalyst must last for 25,000 miles and have at
least 70% conversion efficiency for HC and CO and 30% (yes
that's not a typo) for NOx. Lastly, the catalyst
manufacturer must agree to warranty the catalyst for 25,000
miles including if the OBD system detects a bad catalyst in
those 25,000 miles. These terms just mean the catalyst
manufacter has decided on its own that its cats meet those
requirements. It does not mean the catalyst will have high
enough conversion efficiency to pass your state's IM
tailpipe test (if you have one) or that it will keep the MIL
off for a little while or a long while or that it really
'works' with the OBD system.
'50-state legal' --Another marketing term. CARB approves
cats for use in Calif, the manufacturers self-decide for
cats in other states. Clearly, if the cat does not have a
CARB EO #, it cannot be 50-state legal since it won't be
legal in Calif. A CARB EO # doesn't directly make a cat
legal in other states but since it is solely up to the
manufacturer to decide what is legal in the other states,
they typically would decide that any cat that got a CARB EO
# has to be good enough for other states. (And yes, that is
a very reasonable assumption).
"Direct-Fit" -- A marketing term. Nothing in any regulation
talks about direct fit or not. Typically, catalyst
manufacturers use this to mean it is a bolt-up type part,
not a cut and weld-in type part. It relates only to how the
part is installed and doesn't mean a thing about its
performance. It does not mean it is 'like the OEM' for
catalyst performance or that it has been certified or
verified by anybody.
"Universal" -- Another marketing term. The counterpart to
'direct-fit', universal typically means it is a cut and
weld-in type part and only refers to the method of
installation. Again, it does not mean anything about its
performance (or lack of) nor about its legal uses (e.g., it
doesn't mean it is legal to put on lots of different
vehicles or anything like that).
I won't summarize the new rules again--there have been other
posts on that. This link on our website does indeed have
some other info if you are interested in the California
It has the label decoding that Chris already linked, some
FAQs that we try to keep expanding, some installer tips,
etc. for California-installers and shops.
The bottom line--when Randy or others ask about a Calif cat,
they mean one with an EO and no matter what the sales guy on
the phone tells you, if it ain't got an EO, it is not a
CARB-approved cat that has gone through an approval process.
If you hear direct-fit, think bolt-in installation but don't
assume anything about how well the cat performs. If you hear
universal, think weld-in but again don't assume anything
about how well it performs or what cars it is legal on.
And, while the coverage is still not great, for those
vehicles that do indeed have a CARB-approved cat legal for
it, our testing has shown pretty good durability and
conversion efficiency that makes me comfortable recommending
them to consumers or installers as a reasonable alternative
Mike from California
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