SMOG results 7.4L 1994 - Catalytic Converter work load ?

[kevinvinv]

HI All,

You have been great help over the past year.

Anyhow- I had a question regarding emissions test results.

I finally got the tuning "done" (ended up using a pro) and took it in for a Colorado smog test.

I initially failed and decided to replace the catalyst to see if I could sneak by. That made a HUGE difference... here are my numbers both with the old cat and the new one:




EPA Limit

Old Cat

New Cat














2.00

2.29

0.34



20.00

25.71

4.46






702.93

795.28



4.00

8.89

2.19



The first column is the EPA limit here in Colorado in Grams Per Million (GPM). The numbers I believe are an average taken over the entire dyno test which spans idle to 60MPH cruise.

The first thing of interest is HOW WELL the cat "fixes" the readings.

My concern is whether or not the Cat is working too hard and the engine needs more tuning.

Any thoughts on this?

Thanks!!!

[1project2many]

EPA Limit Old Cat New Cat

HC 2.00 2.29 0.34
CO 20.00 25.71 4.46
702.93 795.28
NOX 4.00 8.89 2.19

I took the liberty of adding the specific components that are tested. I believe the high number is CO2 PPM.

Those #'s aren't that high on the old cat. I don't know if I'd be worried. Is the test performed at idle, or over an RPM range including a simulated load?

[kevinvinv]

Woa, yeah- thanks - I got carried away and didn't cut / paste the whole table.

Thanks! You got the gases correct. And yes- the other number is CO2

Thanks again.