Part of Lesson Plan: **5 Gases (updated) by Michael Fleming
Activity Overview / Details
Before I ever let the students out in the shop, I ask them to place their safety glasses on their faces. I have two students collect the journals and return them to the shelf (I do not allow students to take their journals outside of the shop).
For the demonstration, I use the OTC portable first and conclude with the the ESP on manual test mode which has a larger colored screen. The OTC screen is small, so I usually let a student hold it and ask another student(s) interpret the data. Show them how to calibrate the machine (most 5 gas machines need calibration). Then test the outside air and note the readings.
Next, take the gas cap off and measure the fuel vapors at the filler next (the hydrocarbons should greatly increase). This is important to show that HC is unburned gas going out the tailpipe.
Finally, measure the tailpipe emissions under the following conditions: idle @ normal temp, 2500 rpm, induced vacuum leak, and a rich condition. For the rich condition, propane enrichment is a good choice, or most disconnected sensors do create a rich condition. If nothing else, disconnect sensors as an extension activity. Adding a clogged air filter is another effective way to show how vehicle emissions are affected by maintenance items.
Important: This demonstration should be a fun activity, because its experimenting on ways to affect fuel ratios. Thus, students should give suggestions on what to try. Have fun with it. Try to make the vehicles gross polluters!!!