RE: Headers cause emissions changes, why?

[James Montebello <jamesm@domain.elided>]

Some headers replace catalytic convertors on some cars.  There are headers
available that don't replace them on the GTV6 & Milano (can't speak about
the 164 or any other V6 Alfa).  I believe all of the exhaust system from
the ports on back is subject to EPA anti-tampering laws.  In practice,
replacing anything after the cat is typically allowed.  Anything before
the cat is not allowed to be altered.  The reasons for this have to do
with the response of the cat as it warms up.  Catalytic convertors need
to be hot to work.  Move it farther from the exhaust ports, and it will
take longer to warm up to operating temp (or may never reach operating
temp), thus dirtying the exhaust after a cold start.  A heavy cast-iron
manifold will hold in more of the heat, warming up the cat faster.
A light, thin-walled header will conduct and radiate more of the heat
away before it ever gets to the convertor.

A good many headers are legal in California (have a CARB EO#), although
I don't know of any for the Alfa V6-engined cars.  The CARB certification
process is lengthy and involved, and unless there's a lot of sales volume
to justify the expense, almost no one will bother to go through it.

james montebello

On Thu, 25 Jul 2002 alfaracer75@domain.elided wrote:

> The reason the headers aren't legal for emissions is
> because the headers/downpipes replace the catalytic
> converter. You should be able to install the headers
> along with a high flow cat or two and pass emissions
> testing with no problems.
>
> Joe at Alfacentro did this exact thing, he installed a pair
> of high flow cats with his CSC headers.
>
>
> -Chip
> San Diego, CA
> '89 Milano race project
> http://www.fastalfas.com
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