[Shotimes] High NOx during emission test

[krazgeo@comcast.net]

 -------------- Original message ----------------------
From: "Ron Porter" <ronporter@prodigy.net>
> Cats can cause high NOX? I thought that high NOX was due to high combustion
> chamber temps. Bill's car wouldn't have an EGR (unless it was originally a
> CA car).
> 
> Going back into the memory banks, but doesn't slightly retarded timing
> increase CC temps?? Just wondering.
> 
> Seems like running a load of high-octane gas, alky gas, or a load of Toluene
> may help.

As I remember.....Our cats are "three way" cats....they deal with NOX, unburned HCs, and CO.  The EGR system helps out when NOX needs to be VERY low, as in CA.  High NOX is created by high combustion temps.  Advancing timing increases combustion temps, since it allows combustion to occur longer.  The plug retards timing to 10 degrees BTDC at all speeds.  We have one car out here in our club that is EGR less (from Texas), and has the new multi-piece SHOShop Y-pipe.  For some strange reason, the new cats won't "light-off"; that is, they won't get hot enough to start working.  To get his car to pass, we have to pull that plug.  The exhaust is cool enough at the tailpipes, at idle, even after the car is fully warm and coming off the interstate on a hot day, to leave your hand in it indefinitely.  Sometimes this happens, according to my smog guy, and you just have to put up with it, or get another Y-pipe.

George