[Shotimes] High NOx on Smog Test - Need Ideas

[John J. Weidenbenner]

The Shorting Plug is between and above the firewall and cam position sensor.
It's a two pin female connector with a plastic jumper plug. Black color. It,
when unplugged retards the timing back to 10 ? degrees.

John W.
----- Original Message ----- 
From: "Alan Fanning" <Awfanning@earthlink.net>
To: "SHOtimes" <shotimes@autox.team.net>
Sent: Sunday, February 08, 2004 10:11 AM
Subject: [Shotimes] High NOx on Smog Test - Need Ideas


> I have one of the SHOShop 3.2l, high compression, engines in my '91 SHO.
It
> has stage 1 cams, 80 mm MAF/LPM, and a history of failing smog tests
unless
> the cats are brand new. I bought it 2 years ago from the original owner,
who
> had spent way too much on SHOShop parts and services.
>
> In prior years, th smog tests here were performed at idle and 2500 rpm,
> under no load. Only HC and CO were tested. The car had big problems with
the
> idle test, which I ascribed to too much valve overlap due to the cams. At
> 2500 rpm it ran fairly clean.
>
> Fast forward to yesterday - with my registration expiring today, I had
> procrastinated as long as I could over getting another smog test. The
tests
> are now done on a dyno, at 15mph and 25mph. I found a guy who would do a
> pre-check (results don't go to DMV) for $25, and was willing to experiment
a
> little with which gear to run the car in. You have to be within a
1500-3000
> rpm window. I figured running at the higher rpm's, like before, would be
my
> best chance. However, now they also test for NOx, which proved to be my
> downfall this year. The good news - HC and CO were nowhere near the limit.
>
> At 15mph and 25mph, the NOx limit is ~750ppm. I tested at 1064 ppm at 15
mph
> and just under the limit at 25 mph. The car throws no KOEO codes - I
haven't
> checked the KOER codes.
>
> I know that the higher compression (10.5:1) and cam's can't be helping my
> cause, but can't readily change either at this point.
>
> What else should I check besides the following?
>
> o   EGR operation
> o   EGR passageways in intake manifold
> o   KOER codes
>
> Also, there's a shorting plug on some connector that can be pulled to
> affects NOx? Anybody remember the details on this?
>
> Thanks.
>
>     Alan
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