204D - Emission Control/After Treatment Systems

Question 1

What years were the EGR, DPF, and SCR introduced to meet increasingly stringent emissions regulations?

Answer 1

EGR - 2002
DPF - 2007
SCR - 2010

204D pg. 2

Question 2

During perfect and complete combustion, only ____ and ____ are produced.

Answer 2

Carbon dioxide
Water

204D pg. 3

Question 3

What diesel engine emission forms smog?

Answer 3

Combination of NOx, hydrocarbons, and certain environmental conditions

204D pg. 3

Question 4

What was done to reduce sulphur oxides (SOx) which lead to acid rain?

Answer 4

Sulphur reduction in diesel fuel.
1980’s - LSD 0.05%, 5000ppm
2007 - ULSD 0.0015%, 15ppm

204D pg. 5

Question 5

What technology was used to reach the 2002 emission regulations for a 50% reduction in NOx?

Answer 5

EGR and retarded timing.

Reduces the oxygen concentration in the chamber, producing less heat, reducing NOx

204D pg. 10

Question 6

What are the negative effects of EGR?

Answer 6

Increased CO & hydrocarbons (soot) which requires additional after treatment.

204D pg. 11

Question 7

What are the two basic types of ERG valves?

Answer 7

• Butterfly
• Poppet

204D pg. 12

Question 8

Exhaust gas enters the EGR cooler at about ______ C and exits at about _____ C.

Answer 8

Enters about 700C
Exits about 200C

204D pg. 13

Question 9

During boost operation, the EGV valve is ______.

Answer 9

EGR valve is closed

204D pg. 18

Question 10

The Diesel Oxidation Catalyst (DOC) is made with what precious metals?

Answer 10

• Platinum
• Palladium

204D pg. 21

Question 11

Where is the DOC positioned in the exhaust system?

Answer 11

As close to the engine as possible (in front of the DPF) so the required heat will be available for the catalytic conversion.

Converts exhaust gases into water & CO2

204D pg. 20

Question 12

How does a DPF trap soot and ash through its honeycomb design?

Answer 12

Wall Flow technology.

A plug prevents gas from passing straight through the honeycomb cell. Gases must permeate the substrate material and exit through the adjacent cell.

Gasses are able to pass through to the adjacent cell, but soot and ash cannot.

204D pg. 23

Question 13

During a regeneration, soot in the DPF is converted to: (3)

Answer 13

• CO2
• NO
• Ash

204D pg. 24

Question 14

Hydrocarbons (diesel fuel) are sometimes injected into the exhaust system. When would this occur?

Answer 14

During an active regeneration to produce the required heat needed in the DOC.

204D pg. 25

Question 15

Where are the three temperature sensors located on the DOC and DPF?

Answer 15

• Inlet of DOC
• Outlet of DOC
• Outlet of DPF

204D pg. 27

Question 16

How is a DPF cleaned when removed from the vehicle?

Answer 16

Regulated air is blown through the core and a vacuum collects the ash for disposal.

204D pg. 31

Question 17

What emission is the selective catalyst reduction (SCR) designed to reduce?

Answer 17

NOx

Selective - Targets NOx
Catalytic - uses DEF
Reduction - reduce the emission level

204D pg. 34

Question 18

Where in the exhaust system is the SCR located?

Answer 18

Downstream of the DOC and DPF.

204D pg. 35

Question 19

As DEF is injected into the mixing pipe, it is hydrolyzed (converted) into:

Answer 19

Ammonia, which attaches to the SCR catalyst and neutralizes nitrogen oxides.

Output is water and nitrogen.

204D pg. 35

Question 20

DEF is composed of:

Answer 20

67.5% water
32.5% urea

204D pg. 46

Question 21

If the DEF system has been run low, how many litres of DEF must be added into the DEF tank for the ECM to reset the system and remove engine de-rates and speed limits?

Answer 21

20 litres (5 gallons)

204D pg. 38

Question 22

The SCR unit is composed of what two catalysts?

Answer 22

• SCR catalyst
• Ammonia oxidation catalyst (reduces residual ammonia that slips through the SCR catalyst)

204D pg. 43

Question 23

What is the approximate shelf life of DEF when stored at 29 degrees Celsius?

Answer 23

1 year

204D pg. 46

Question 24

Initial Tier 4 emissions were introduced for off-road equipment in what year?

Answer 24

2011

Question 25

If the yellow DPF lamp is illuminated (solid), the operator should:

Answer 25

Increase the duty cycle and load the engine.

204D pg. 28

Question 26

If the soot loading on a DPF rises above 80%, the engine will:

Answer 26

Undergo a severe de-rate and shutdown.

204D pg. 28

Question 27

A DPF soot loading of 60% is indicated by:

Answer 27

A moderate engine de-rate and flashing yellow DPF lamp.

204D pg. 29

Question 28

Durring a regeneration, the exhaust outlet temperature of a DPF system will reach:

Answer 28

593C / 1100F

204D pg. 25

Question 29

The SCR system is primarily used to reduce what emission?

Answer 29

NOx

204D pg. 35

Question 30

What emission is the EGR designed to reduce?

Answer 30

NOx

204d pg. 10

Question 31

In boost mode, the EGR valve is in what position?

Answer 31

Closed. To not rob the turbo of exhaust pressure.

204d pg. 18

Question 32

During brake mode, the EGR valve is in what position?

Answer 32

Closed

204d pg.17

Question 33

When an EGR is in recirculation mode, what position is the EGR valve in?

Answer 33

Open

204d pg. 17

Question 34

How are the EGR and turbo used in conjunction with each other?

Answer 34

To direct the exhaust gas through the EGR, a pressure differential is needed. A VDT or VGT creates this needed backpressure as it slides the turbine nozzle or pivots the vanes.

204d pg. 17