Week 4, Light Duty Diesel Emissions Flashcards
- Liquid and solid particles emitted from the engine exhaust and crankcase
- Black carbon results in soot emissions; eliminated with newer diesel engines
- Regulated and classified by particulate size in four categories
Particulate Matter
Chassis ________________ measure emissions based on distance travelled by the complete vehicle
Dynamometers
What is a common method to measure smoke density of diesel engine exhaust?
Opacity Testing
- Inadequate combustion time
- Improperly mixed fuel and air
- Coarse spray droplets
- Insufficient combustion heat
- Fuel pressure too low
These are all common causes of…
Incomplete combustion
Regulating _______ (a naturally occurring component in diesel fuel), it enables sophisticated exhaust emissions’ aftertreatment
Sulfur
High fuel sulfur content destroys ability of sulfate production devices to convert _________ emissions to __________ emissions
Noxious (harmful); Nonharmful
Diesel engines are governed at relatively ____ engine speeds
Low
First standards to reduce diesel emissions were introduced in _______
1970
Diesel fuel sulfur content was reduced to __% in 1993
1
Prior to 2007, emission reduction was accomplished in the ______________
Cylinder
- Indicate the level of emission standard an engine was designed to achieve
- Provides information about part replacement and adjustment procedures, software calibration files, and other relevant data that affects emissions
Emissions Decals
- Light duty: 110,000 miles or 10 years
- Medium duty: 185,000 miles of 10 years
- Heavy duty: 435,000 miles or 10 years
These are all examples of…
Useful life requirements
- Low and high pressure cooled EGR
- Two-way oxidation converters
- Diesel particulate filters
- Etc.
These are all examples of…
EPA-07 Standards
From 2004-2010, NOx emissions had to be reduced by _____
90%
The biggest technical challenges with diesel catalysts are…
- Cold exhaust temperatures
- Excess air content in exhaust
A(n) _________________________________ causes oxygen to chemically combine with noxious emissions such as HC and CO
Oxidation catalytic converter
_____________________ systems were introduced to help achieve a 90% reduction in NOx emissions
Selective catalytic reduction
Oxidation process turns emissions into _____________
Water
Oxidation converters consist of a stainless-steel canister called a _____________
Substrate
Substrate in a catalyst has a washcoat of catalytic ________________________
Precious metals
Diesel catalysts need a minimum temperature of _______ before O2 can oxidize
400°F
Reduction of pungent diesel odor is a ______________
Byproduct
Exhaust is diluted with air, which _________________ its temperature
Reduces
Technology incorporates HC-trapping materials into a catalyst substrate called _______________
Zeolite
Low-temperature oxidation catalysts begin to catalyze at approximately _______
360°F
What component removes soot and other solid particles from diesel exhaust, rendering the exhaust completely smokeless?
DPF (Diesel Particulate Filter)
DPF’s eliminate particles down to ___ nanometers
50
Exhaust passed through a wall _____________ where gas can escape but PM is trapped
Flow filter
When DPF’s eventually become clogged, _______________ clears out the filter
Regeneration
Heat for regeneration either comes from ________________ or __________________
Exhaust gas; added fuel
_________ Regeneration
- Takes place 85% of the time
- No fuel is added
- Vehicle must be 30+mph for 20 minutes
Passive
The DPF is heated by adding small amounts of fuel to the exhaust stream. A downstream oxidation converter produces heat through a catalytic reaction of the fuel
Active regeneration
In active regeneration, exhaust temperatures can raise to over _______
1000°F
A fault code is set when a soot load of ____ is reached
80%
Late injection in the exhaust stroke can cause ___________ in engine oil
Fuel dilution
__________ regeneration requires vehicle to be away from combustible material
Parked
DPF catalyst substrate is available in different materials such as…
- Cordierite
- Silicon carbide
- Metal foil
What can accumulate inside a DPF? (result of burned oil)
Ash
What is the process called where liquid urea is sprayed into exhaust stream to destroy NOx molecules?
SCR (Selective Catalytic Reduction)
NOx ______________________ is a catalyst strategy for removing NOx in the low-temperature, oxygen-rich exhaust environment of diesel engines
Absorber technology
Lean NOx refers to __________________
Oxygen content
The process in which NOx emissions are temporarily stored in the catalyst and removed in a two-step process that introduces fuel-rich oxygen-depleted exhaust
NOx Adsorbing
What are the two drawbacks in DeSOx reactions?
- NAC aftertreatment requires increased fuel consumption
- Sulfur deactivates NACs
A variety of ______ are needed to make DPFs work
Sensors
Which sensor measures exhaust pressure at DPF inlet and outlet and supplies that data to the ECM?
Differential pressure sensor
Most DPFs use _______ temperature sensor
Three
____ sensors do not provide closed-loop feedback to meter the correct amount of DEF, but can detect incorrect concentrations of DEF emitted by dosing injectors and other emission related faults
NOx
What component produces NH3 in the engine exhaust using HC dosing, high EGR flow, and reduced oxygen content without fluid additives?
NAN/LNT components
- When DPF soot loading exceeds 80%, the driver should change driving conditions to initiate a DPF passive regeneration
- If passive regeneration cannot be completed, an active regeneration must be done
- Engine must e warm and left at low idle, parking brake applied, and DPF inhibit switch held
These are all necessary when performing an…
Active Regeneration Procedure
- Initiated using an electronic service tool or OEM software
- Light-duty vehicles cannot be regenerated by dash switches
- Heavy-duty vehicles may not be able to complete active regenerations
These are all necessary when performing a…
Forced DPF Regeneration
____ will accumulate from engine oil and eventually DPF will need to be removed for service
Ash
_________________________ is a major emission problem in diesel engines due to higher compression ratios, cylinder pressure, and temperatures
NOx formation
EGR may incorporate the use of a ________________ to help draw in EGR gases
Throttle plate
Provide the ECM with data about quantity of air and exhaust, conditions that enable and disable EGR flow, and diagnostic data for the OBD system
EGR System Input Sensors
Engine speed and accelerator pedal position indicate how much EGR mass is required for engine; combined with intake manifold pressure and temperature and determines the weight of air entering the cylinders
EGR Mass calculations
The OBD II system detects and measures whether correct EGR flow is enabled based on a reduction in airflow into the engine
MAF Sensor and EGR Flow Calculations
EGR gas flows through a venturi, which has a sensor measuring the pressure on its inlet and outlet sides. Low flow produces a low differential, high flow produces a high differential. Combined with gas temperature data, an accurate measure of EGR flow can be achieved.
Pressure Differential Measurement of EGR Flow
Exhaust gas temperature must be lowered to roughly 425°F before it enters the cylinder. An EGR cooler is a heat exchanger that transfers heat from EGR gas to the cooling system. All cooling system components must be able to withstand the additional heat load
EGR Coolers
What tools are required for diagnosing an external, non-cooled EGR?
- Vacuum gauge
- Multimeter
- Scan tool
