Inspect turbocharger(s), wastegate, and piping systems; determine needed action. Remove and reinstall turbocharger/wastegate assembly
Lesson Plan for
DIT 112 Diesel Engines
Course HS Title: / Diesel Engines / Program:KCTCS Courses included in HS Title: (Lesson is prepared for course highlighted.)
KCTCS Course No. / KCTCS Course Title
DIT 112 / Diesel Engines
Introduction/Context / This lesson will instruct the student on how to inspect turbocharger(s), wastegate, and piping systems, and determine needed action, and remove and reinstall turbocharger/wastegate assembly. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in a Diesel Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Prepared By / School / Date:
Grade Level / No. Students / No.IEP's: / Lesson Length:
Task
Inspect turbocharger(s), wastegate, and piping systems; determine needed action.
Remove and reinstall turbocharger/wastegate assembly
Objective
Given the proper tools and instruction, the student will be able to inspect turbocharger(s), wastegate, and piping systems, determine needed action, remove and reinstall turbocharger/wastegate assembly, and pass a written test covering the task with 100% accuracy.
Connections:
Skills Standards:OH 001
OH 002
OH 003
OD 002
OD 003
OD 005
Common Core Technical Standards:
TD-SYS-2
New Common Core Standards:
RST 11-12.2
RST 11-12 3
INSTRUCTIONAL MATERIALS/TECHNOLOGY
Teacher Designed Materials and Other Handouts
Textbooks and Workbooks
Various / Diesel Engines ASE Test Prep / 2007 / Delmar / 46-47
Equipment
As Needed / Dial Indicator / Various
Content/Presentation/Demonstration Outline
Tell students that Variable Geometry turbochargers rotate more slowly and develop boost at lower rpms, reducing turbo-lag time. The resultant increase in air density increases engine output. Explain that modern variable geometry turbochargers tend to rotate at slower speeds.
Inform students that compressing air in a turbocharger heats it up. To reduce the effects of superheating, tell them that a heat exchanger, known as an aftercooler, is located between the turbocharger and the cylinders. Explain that while the commonly used aftercooler is an air-to-air heat exchanger, some engine manufacturers prefer to use an air-to-water heat exchanger, called an intercooler. Regardless of the method used, the result is increased efficiency because cool air is denser.
Instruct them that the rotor on the exhaust side of the turbo is called the turbine because it is driven by exhaust gases. The impeller of the intake side is called the compressor because it compresses the air charge to the engine. Tell them that as exhaust gases drive the turbine, the compressor is rotated. Explain that rotation of the compressor causes air to be drawn from the outside through the filter and into the inlet side of the compressor. Let them know that pressurization causes the air to heat and additional heat is transferred from the turbine through the shaft to the compressor and to the compressed air.
Inform students that this hot pressurized air is routed to the aftercooler where it is cooled and directed to the intake manifold. After combustion, hot expanding gases are routed through the exhaust manifold to the turbine inlet. Tell them that the hot gases turn the turbine and exit through the outlet to the exhaust and muffler.
Explain that some turbochargers use an electrically or mechanically controlled valve to route a portion of the exhaust gases around the turbine. Tell them that this valve is referred to as a wastegate or over-boost protection valve, and prevents the turbocharger from over-boosting the cylinders at high engine rpm. Let them know that modern electronic systems incorporate a boost sensor to monitor the turbocharger and an electronic module to control the wastegate of over-boosts valve.
Tell students that when inspecting a turbocharger, they should start with a visual inspection. Have them check the turbocharger outlet for the presence of oil. Oil in the outlet would indicate the turbocharger seals might be leaking. The seals may be worn or their leakage may be caused by a restricted air cleaner, a turbocharger oil drain that is restricted or improperly routed, or by high crankcase pressure. Instruct them to visually inspect the turbine and compressor wheels for damaged blades, and check the turbocharger shaft for axial and radial end play and compare to specifications.
Instruct students that when damaged blades or end play that is out-of-spec is found, they should check for damage to the housings. If the housings are also damaged, let students know that the turbocharger should be replaced as an assembly. If the housings are still serviceable, the center housing rotating assembly (core) may be replaced. Explain that it is a pre-balanced assembly, so recoring is merely a matter of transferring the housings, and the students should be careful to observe the correct alignment.
When recoring, or replacing a turbocharger, tell students to pour clean oil into the oil supply line filling to pre-lube the turbocharger before starting the engine. Explain that some of the causes of turbocharger failures are hot shut-downs that produce warped shafts and bearing failures, turbocharger overspeed from high-altitude operation or over-fueling, lubrication-related failures, and ingestion of dirt or foreign objects.
Applications/Practice
Evaluation and feedback Prior to Testing or Lab Work
STUDENT ASSESSMENT:(Assess student progress with performance criteria.)
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)