Date:         Wed, 25 Aug 2004 17:19:59 -0700
Reply-To:     laurasdog@WEIRDSTUFFWEMAKE.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steve Delanty <laurasdog@WEIRDSTUFFWEMAKE.COM>
Subject:      Re: Failed Emissions Check
In-Reply-To:  <b3a1e7ad04082516333adf699b@mail.gmail.com>
Content-Type: multipart/mixed; x-avg-checked=avg-ok-43BA2A03;

At 04:33 PM 8/25/2004, Craig Oda wrote:

>This is interesting.  Are you saying here that you moved the timing
>from 5 degrees BTDC to TDC and your emissions improved?   Why would
>this improve emissions?  Did your emissions test for NOX as well as
>HC?  <snip>

----------------

It's a common hot-rodder trick to retard the timing to pass NOx test.
It reduces the combustion temperature and pressure which reduces NOx.
The smog guys are supposed to check ignition timing, so you can't set it
too retarded, but usually if it's only a couple degrees retarded from spec
they don't say anything. I knew someone who went to the trouble of
installing the crank pulley (with timing marks) with an offset key so that
when the timing marks "looked right" with a timing light, it was  actually
about 8 degrees retarded.from stock. it enabled him to slip his his 428 FE
Ford motor with 10.75:1 compression past the smog guys.
The engine actually tested very clean except for NOx...

Retarding the timing MAY also increase HC, so there is a tradeoff.




Steve
'86 Westy "Escape Pod"
'73 Beetle "ain't got a name yet"