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VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
VVC AUTO 85.5 - Smog Technician - Level 1 - Nox
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VVC AUTO 85.5 - Smog Technician - Level 1 - Nox

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  • 1.  Module I  Module goals  How NOx is created  How temperature affects NOx  How compression affects NOx  How EGR affects NOx  How A/F ratios affect NOx  Post combustion controls to reduce NOx  How cats reduce NOx
  • 2.  Vehicle emissions have been controlled since PCV systems were introduced in 1961  Early exhaust diagnosis was done using CO & HC  Later 02 & C02 was used
  • 3.  NOx was associated as a key player in the production of photo chemical smog in the late 60’s  Efforts to reduce CO & HC caused NOx to increase  Module 1 addresses NOx  Formation  Control
  • 4.  The internal combustion engine is a large air pump  Oxygen = 20% = small amount of what is drawn into the engine  Nitrogen = 80% = Large amount of what is drawn into engine  Plus a very small amount of inert gas  As an engine wears NOx forms
  • 5.  Two ways to control NOx  Precombustion  Before combustion  Post-combustion  After combustion
  • 6.  Precombustion controls  Keeps combustion chamber temperatures below 2500 degrees Fahrenheit  Lower compression ratios  Less compression = less heat  Richer A/F ratios  More fuel = less heat  When A/F ratio reaches 16:1 NOx decreases (lean misfire)  EGR systems lowers combustion temperature.  Computer Programming  Retarded timing  Richer A/F ratios
  • 7.  Post-combustion controls  After combustion  Three way Catalytic Converters  Catalytic Converters are a secondary method only – they will not overcome excess NOx created by the engine.
  • 8.  Ignition timing  Initial & total  EGR system  Must pass functional test  Fuel octane  Low burns too fast and tends to explode!  Air intake temperature  Air duct or cooling systems problems  Carbon buildup  Increases compression  Hot spots  Air pump operation  Must divert  Dirty fuel injectors  Restricted or bad pattern  Lean engine operation  Lean = heat, lean fuel mixture burn too slow!
  • 9.  Other early precombustion systems  Spark control -- controls timing advance  TAC -- preheats intake air when cold  EGR -- recirculates exhaust gasses to lower combustion chamber temperatures  EFE -- heats intake manifold
  • 10.  Combustion chamber carbon treatment  Run additive through engine to burn off carbon  NOx diagnosis = think what will cause heat

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