[Diy_efi] Emissions Numbers...

[Mike Frels]

Seeing as I have been having so much trouble getting the fueling straight on my new Vortec headed TPI engine I took my car to a local inspection stop today and got a treadmill emissions test. Here in Fort Bend county SW of Houston, Texas I learned they do a two stage test. One minute at 15mph and one minute at 25mph. Both runs in second gear. It's done twice with the best readings of both runs being the ones they accept and use. Even though I knew my car would not pass seeing as I still have not found the root cause of the idle/low speed 160 BLMs that I am getting I found the results interesting. BTW my car did fail. It flunked the NOx during the 15mph runs. Here are the results they handed me. 

25mph:
HC(ppm) std-148 reading-65
CO(%) std-.94 reading-.36
CO2(%) 12.9
O2(%) 2.9
NOx(ppm) std-1047 reading-660
Dilution(%) std->6 reading-13.3

15mph:
HC(ppm) std-152 reading-108
CO(%) std-.86 reading-.37
CO2(%) 13.3
O2(%) 2.3
NOx(ppm) std-1146 reading-1635(*FAIL*)
Dilution(%) std->6 reading-13.7

If I remember right high NOx numbers are usually a result of high combustion temperatures due to lean conditions. Seeing as my less than smooth idle feels like I am not firing evenly I am thinking that I may have an injector or two on the O2 sensor side of the engine that are either somewhat clogged or not opening properly at low speeds. Any thoughts?

BTW anyone know what "Dilution" is?

Oh yeah, one more interesting is that I received passing higher speed readings even though I have a hollow cat.

Mike
'86 Z28
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