Automotive General Services Technician Model

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Transportation

Lesson Plan Originally Created By: Michael Fleming

**5 Gases (updated) by Michael Fleming

Part of Unit: Engine Performance

Lesson Plan Overview / Details

Students will learn about the 5 gases used to diagnose vehicle emissions.

Lesson Time

1 Hour Instruction 1 Hour Lab
2 Days

Objectives and Goals

Students will understand the theory behind vehicle 5 gas emissions and fuel ratios. Student will use the knowledge to perform emission testing on shop vehicles using a 5 gas analyzer.

Activities in this Lesson

  • Vehicle Emissions - Hooks / Set

    Write on a white board the words "vehicle emissions." Ask students to describe what vehicle emissions are (can you see, smell, feel, hear or measure them?). Write down all their answers and then show the You Tube video.

    After the video, ask if the exhaust emissions on the Mustang were normal or abnormal. Since there is smoke, ask what color it is (white / blue). Talk about driving conditions in that we do not know if the vehicle is cold or hot. Mention that a small amount of white smoke is normal when vehicles are cold. Guide the discussion to what is a perfect combustion (too litlle or too much fuel).

  • 5 Gas Introduction - Lecture

    Have students take notes while you show the PowerPoint that talks about good and bad gases.  Elaborate that a perfect combustion will produce less than 2% Oxygen, 14 - 15% Carbon Dioxide, and H2O. Also elaborate how fuel ratios affect not only the good gases, but the bad ones as well:  Hydrocarbons, Carbon Monoxide, and Oxides of Nitrogen. 

    The slides do briefly discuss emission systems, which should be mentioned as well. As you are discussing each emission, the students should be writing down the notes. The last slide is crucial because it will be their assessment, so discuss each line in detail through the different fuel ratios.

  • 5 Gas / Fuel Ratio Analysis - Lecture

    The attached individual descriptions and graphs can be composed as a study packet or used on a document camera. My preferred method is to transfer the information to the white board, so that you model the drawing of the graphs and the notes.  Emphasize patterns and characteristcs of the gas as it relates to fuel ratios and point out how each gas is measured. Also point out reasons for gas exculation or decline other than fuel ratios.

    If you have the students keep a journal as I do through the year, they can use the notes for any tests. My midterm and final is composed from the top two note books in the class.

  • 5 Gas Analyzer Demonstration - Demo / Modeling

    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!!!

  • Vehicle Inspection Reports: VIRs (Day 2) - Lecture

    Start the second day with the PowerPoint again to briefly go over the 5 gases. The last two slides will be the ones to focus on. Talk about why the vehicle failed smog (what gas?). Since it is Day 2, you can discuss an ASM (Acceleration Simulation Mode) test verse TSI (Two Speed Idle) tests.

    After discussing the VIR, go to the next slide and ask students to recognize the pattern of individual gases as the fuel ratio changes. You can also ask what systems and factors contribute to fuel ratio changes.

  • 5 Gas Analyzer Lab Day - Lab / Shop

    Explain to the students that they will now go out in the shop and perform the same 5 gas analyzer procedures you demonstrated the previous day. They will work in teams and each student must be involved in testing the vehicle.  In other words, each student must handle and operate the analyzer. Remind them to calibrate the machine and to test the open air and gas tank filler neck. Explain to them that they may not disconnect sensors until they have completed the lab exercise and been stamped off.

    Before the labsheet is passed out, go over safety. Have everyone place their safety glasses on their face. Talk about the dangers of carbon monoxide poisoning, in that all cars must be outside the shop. Also explain the wheels should be chucked, the parking brake applied and the car is placed in neutral or park.

  • Group Discussion - Closure

    I provide closure by creating dialogue with the students in the group setting. After I stamped off a group on the activity, I ask the students to summarize what they have learned, and I ask for their thoughts on the usefulness of the tool (how & when the skill would be used in an actual shop).

Assessment

Assessment Types:
Journals, Teacher-Made Test, Observations,


I give a weekly grade for notetaking. The notes should be legible and organized. For this lesson though, I have a test that is half test and half lab. The first half is a series of questions for students to interpret a graph showing the 5 gases with different fuel ratios. The second half is a lab activity involving using a 5 gas analyzer. The students must follow the instructions to prep the car and record the changes in emission readings. Basically, they will be performing the same procedure used in the  demonstration.

As students perform the lab exercises, I walk around and ask questions to check for comprehension. If the students prove to be proficient, then I stamp off the groups papers. After they earned the stamp, they may then proceed and experiment by disconnecting sensors one at a time to see emission changes.