What's the trick to redue NOx counts during an emission test?

I know that for HC counts, you retard the ignition timing... but what about NOx counts?

How much do I need to retard the timing to considerably reduce the NOx counts? Is 2 deg enough to knock down 1000 ppm of NOx?


[Modified by Cosworth, 8:19 PM 6/2/2002]

 

more fuel helps reduce NOx, thats what helped me pass emissions (1200ppm down to 192ppm)

Brian

 

Timing was at 16... I set it to 18 now. Should I go higher? I don't have a fuel pressure regulator to increase the fuel manually.

 

retarding the timing will reduce HC and NOx..............

 

fug, I think I have it all mixed up. Correct me if I'm wrong.

1. Retard -> rotate the distributor away from the firewall
2. Advance -> rotate the distributor towards the firewall

Also, when I check the timing w/ a timing gun there are 3 lines on the belt. The middle one is <u>red</u>. So, if I retard the timing which line should the pointer be lining up with? The line left (towards the fender) or the line on the right (towards the firewall)?

__ firewall
__ red (driver side fender)
__ fender


[Modified by Cosworth, 8:19 PM 6/2/2002]

 

hmmm

 

I dunno what your "aircare" stations are like...

but for me when I go and test my car, I keep my foot on the gas and rev it to about 1500rpm and that really puts some heat into the cat.

Apparently it works better when really hot. Maybe it'll work for you.

FWIW, my car which is "vintage" 97 tested cleaner now than it did a few years back with this "trick"

 

Yes, you must make sure that your cat is nice and hot! A cool cat does no good.

I've had hig NOX on my '95 Civic. The place that I took it recommend a full fuel system clean, including the combustion chambers. Apparently the carbon will build up in there, and somehow that will cause higher NOX levels. They did it, (It was expensive, like $90, some big machine by Snap-On), and it cut the NOX levels drastically. It allowed my car to pass!!! FYI...