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CIS %CO vs Duty Cycle Data 1990 M103
Hello,
I recently had my car emissions tested and luckily it passed. I had been using a Gunson Gas Tester but it failed the last time I used it. I set the duty cycle at 40-45% and hoped for the best. After the test I asked the shop owner if I could pay for some time on his machine so I could record so data and find an appropriate setting for the car.
Attached is the data I took which I graphed in Excel. This is prescriptive but I thought it would be an interesting discussion to look at real data instead of general thoughts and opinions about adjusting your CIS.
Note: These are tailpipe reading after the CAT so I didn't expect to see a large deviation.
What I think I learned is that, for my car in it's current running condition:
1. A leaner setting around 55% yielded the best numbers for both %CO and HC PPM.
2. There is a dip in the numbers around the 35% duty cycle range. I'm hypothesizing that this corresponds to a more complete burn and it also correlates to a smooth running engine. It was slightly rougher at the leaner settings.
I hope you find it useful to see this data and maybe it will give you some insight about what is going on when you adjust the mixture on your CIS
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