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Emission Control & After Treatment Systems Flashcards

1
Q

What are the 4 most harmful emissions are?

A

CO
NOx
PM
SOx

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2
Q

Smog is the result of?

A

NOx’s mixed with HC’s in certain environmental conditions

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3
Q

What are the 3 main sources of particulate matter?

A

Unburnt fuel in the form of carbon
Ash from diesel fuel
Soluble organic fractions or heavy hydrocarbons from fuel and oil

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4
Q

Ultra-low sulphur diesel has a sulphur content of?

A

0.0015% or 15 PPM

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5
Q

Engine emissions are measured in what?

A

Grams per horse power hour

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6
Q

EGR is used to reduce what emission?

A

NOx

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7
Q

EGR Causes an increase in what?

A

CO

HC

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8
Q

What are the main components of a EGR system?

A

EGR valve, EGR cooler, Charge air mixer, VDT, EGR piping

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9
Q

EGR valve

A

Controls the flow of exhaust gases to the intake mixer. two basic types of valves are butterfly and poppet

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10
Q

EGR cooler

A

Cooler designs are air to water. Gas enters cooler around 700F and leaves at about 200F

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11
Q

Venturi

A

A specially shaped tube that has a restriction and creates a pressure drop when exhaust gas passes through the restriction. How the ECM measures the flow of EGR gas

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12
Q

Delta P valve

A

Sensor device that measures the pressure differential across Venturi. Has one sensor on inlet and one on restriction.

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13
Q

How does the turbo push more exhaust through ERG?

A

By closing the vanes increases the exhaust back-pressure, which creates a higher pressure in exhaust.

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14
Q

EGR flow depends primarily on?

A

Engine load and temperature

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15
Q

Diesel Oxidation Catalyst (DOC)

A

A canister placed in series with the exhaust system to purify the exhaust gases. Contains a catalyst the causes a chemical reaction with the exhaust gases. Is a flow through design

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16
Q

What is a catalyst?

A

A substance that makes a chemical reaction occur faster or at a lower temperature then is normally required

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17
Q

The catalyst material that is ideal for a DOC?

A

Precious metal elements such a platinum or palladium

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18
Q

The catalytic conversion process allows exhaust contaminants to oxidize at a temperature of?

A

600 - 700 F

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19
Q

What is converted in the DOC?

A

HC, CO, O2 come into contact with catalyst and heat, they combine to form CO2 and H2O

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20
Q

Diesel particulate filter (DPF)

A

Is designed to filter out the exhaust particulates by trapping soot. The ceramic core is made up of a honeycombed shaped, porous substrate.

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21
Q

What is order of exhaust flow for shop test?

A 
Dosing valve
DOC
DPF
Decomposition chamber
SCR catalyst
AMOX`
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22
Q

What are the two basic levels of regeneration?

A

Passive

Active

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23
Q

Passive regeneration

A

Occurs during normal engine operation when the engine exhaust temperatures are above 260C or 500 F. It does not require a hydrocarbon injection

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24
Q

Active regeneration

A

Requires hydrocarbons (diesel fuel) to be injected into the exhaust stream. The hydrocarbons react with the catalyst in the DOC core to produce heat. Temperature can reach 1100 F or 593 C

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25
Q

What are the 3 ways that active regeneration can be initiated?

A

The ECM during driving cycle
DPF dash switch - referred to as a parked or stationary regeneration
OEM diagnostic program

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26
Q

What are the two ways that HC’s are injected into the exhaust stream are?

A

A dosing valve and fuel lines located in the exhaust stream downstream of turbo
Pulsing the engines fuel injectors on the exhaust stroke, only works with HPCR or HEUI

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27
Q

How does the ECM typically monitor the regeneration cycle?

A

Using 3 temperatures sensors and 2 pressure sensors

28
Q

Where are the 3 temperature sensors located in DOC/DPF?

A

Inlet of the DOC, Outlet of the DOC, DPF outlet

29
Q

What is soot loading?

A

The percentage of the DPF that is loaded with soot

30
Q

What happens when the DPF reaches a 80% soot loading?

A

The DPF light continues to flash, the check engine light comes on and the engine begins to de-rate. The DPF is now at max capacity. At this point the operator must park the unit and attempt to force a regeneration using the dash switch.

31
Q

What is the function of the HEST lamp?

A

Inform the operator that the exhaust system is hot. programmed to illuminate only when exhaust temp reaches 450 C / 842 F and vehicle sped is under 8KM.

32
Q

What is the function of the DPF warning lamp?

A

Inform the operator that the DPF needs regeneration

33
Q

Selective Catalyst Reduction (SCR)

A

Selective - focuses on treating a specific chemical, NOx
Catalyst - After treatment device requires a catalyst to be added, DEF
Reduction - After treatment process reacts to reduce the selected emission

34
Q

The catalyst element operates at what temperature?

A

200 - 550 C

392 - 1022 F

35
Q

What chemical reaction occurs in the catalyst?

A

NOx and NH3 (ammonia) react and neutralize, they convert to H2O vapour and N2

36
Q

What 4 molecules leave the exhaust pipe after the SCR system?

A

H2O, N2, O2, CO2

37
Q

DEF is composed of what?

A
  1. 5% H2O

32. 5% Urea

38
Q

Once low DEF has caused a system de-rate, how much must be added to system to return to normal function?

A

Minimum of 20 litres

39
Q

DEF filter

A

typically mounted on the pump and it removes impurities that could plug the orifices in metering valve, or injection nozzle

40
Q

DEF metering unit

A

Sends a specific quantity of pressurized DEF to the injector. Uses air pressure to pressurize the DEF

41
Q

DEF injector

A

Is mounted on the decomposition chamber. It receives pressurized DEF from the metering unit and sprays it into the mixing pipe before the SCR catalyst inlet.

42
Q

What 2 parts make up the SCR catalyst?

A

The an SCR catalyst and a Ammonia oxidation catalyst (AMOX)

43
Q

What is the purpose of the AMOX catalyst?

A

To break up any residual ammonia that slips through the SCR catalyst

44
Q

DEF will start to freeze at what temperature?

45
Q

What is the largest effect of emissions control on the fuel system?

A

The mandating of ultra low sulphur diesel

46
Q

What emission is reduced by the use of EGR?

47
Q

Initial tier 4 emissions for off-road were introduced when?

48
Q

With the EGR System, Introducing exhaust gases into the intake manifold is done to reduce the engines:

A

Combustion pressure and temperature

49
Q

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

A

Undergo a severe de-rate and shutdown

50
Q

A plugged DPF or DOC can cause:

A

Excessive exhaust system back pressure

51
Q

What are the sensors located on the SCR catalyst?

A

A NOx sensor located on the inlet and the outlet.

A temp sensor located on the inlet and the outlet.

52
Q

After the ammonia and exhaust gases pass through the SCR catalytic converter, the NOx emissions are converted to?

A

Nitrogen and water vapour

53
Q

The DEF tank is constructed of ___________ or_________?

A

Plastic or Nylon

54
Q

To monitor the regeneration cycle of the exhaust system the ECM uses _______ temp sensors and ________ pressure sensors.

A

three (3) temperature

two (2) pressure

55
Q

What are two basic types of EGR valves?

A

Butterfly and Poppet

56
Q

The four most harmful emissions are:

A 
carbon monoxide (CO)
oxides of nitrogen (NOx)
particulate matter (PM)
sulphur oxides (SOX)
57
Q

DEF will freeze at what temperature?

A

-11 C or 12.2 F

58
Q

DEF fluid consist of ____% water and ________ urea.

A
  1. 5% water

32. 5% urea

59
Q

What is the DEF filter service interval?

A

two (2) years or 320,000 KM (198,839 mi)

60
Q

In the SCR catalyst system the exhaust heat catalyst. The element operates between ______ C and _______ C.

A

200C (392 F) to 550C (1,022F)

61
Q

What does HEST mean and what does it do?

A

High Exhaust System
Temperature
Informs the operator that the exhaust system is hot.

62
Q

The DPF should be cleaned at approximately _______?

A

200,000km on road

2500 hours off-road

63
Q

The catalytic conversion process with DOC allows exhaust contaminants to oxide at a temperature of ______ to ______.

A

600F to 700F

64
Q

The catalytic conversion process without DOC will not occur below ______ to ______.

A

1100F to 1200F

65
Q

What is the result of unburned or partially unburnt fuel?

A

hydrocarbons

Electronic Fuel & Emission's (4 decks)

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