Air Induction and. Systems. Diesel Engine Technology For Automotive Technicians. Understanding & Servicing Contemporary Clean Diesel Technology

Transcription

1 Air Induction and Crankcase Ventilation Systems Diesel Engine Technology For Automotive Technicians Understanding & Servicing Contemporary Clean Diesel Technology

2 Requirements of Combustion Diesels are air consuming machinery 2

3 Airflow & Diesel Combustion Intake 3, RPM Diesel 6.0L Gasoline ~ 6.0L Powerstroke Diesel 732 CFM 160 CFM Diesel combustion has much higher airflow requirements than gasoline engines 3

4 Requirements of Diesel Combustion High intake airflow means diesel s are sensitive to the quality of intake air. To provide best performance fuel economy and lowest emissions diesel engines intake air must be: Clean Adequate supply Dry Fresh Relatively cool 4

5 Adequate Air The flame temperature of diesel fuel is 3,990F Diesels need excess airflow to dilute the heat of combustion. 5

6 Adequate Air International T-444E Intake System Large intake systems (and exhaust) are needed on diesel to supply an adequate intake air flow 6

7 Adequate Air Supply Diesel fuel requires more air mass to burn than gasoline (14.7:1 gas Vs 20:1 - #2-D fuel) 7

8 Clean Air Diesel engines need clean air to prevent excessive engine wear. Dirt entering the engine will contaminate the lube oil causing premature wear in places such as engine HEUI injectors, turbocharger bearings and plug oil cooler nozzles 8

9 Dry Air Foggy Moisture Laden Air Normal Humidity Sea Level Air Water vapour (fog, rain, snow, high humidity) displace oxygen in the air. High humidity can increase engine emissions and lower engine power output. Hot humid summer days can be the worst for diesels. 9

10 Cool Air Hot air contains less oxygen than cool air. Cooler air produces more power and fewer emissions 10

11 Other Air Intake Requirements Diesel intake systems are noisy due to turbochargers noise and large amount of valve overlap in a diesel exhaust pulses travel up into the air intake. 11

12 Noise Reduction To Turbocharger Inlet From Air Filter This air intake pipe on Dodge Rams is designed to dampen intake noise 12

13 Noise Reduction Noise Dampening Resonator The air intake on this DMAX 6.6L has a resonator box connected to the turbo inlet. Used to dampen intake noise from valve overlap and the turbocharger. 13

14 Air Intake Heating To improve cold start-up and reduce emissions during warm-up, diesels intakes often use electric intake heaters. 14

15 Air Intake Heating Heater Intake Pressure Sensor Intake Air Temperature Sensor Air intake heaters are controlled by the ECM. Intake temperature and boost pressure are common inputs used to determine whether to heat the air. The heater will shut-off when the turbocharger is boosting (air temperature increases) ceases) 15

16 Air Shut-off Device Intake Manifold Switch Over valve Intake Air From Intercooler EGR Valve EGR Cooler Diesel high compression ratio causes the engine to shudders when the ignition is turned. An intake manifold flap change-over valve shut-off intake air when the ignition is switched off on this VW TDI 1.9L diesel 16

17 Intake Air Turbulence Intake air turbulence is needed to help pprepare p the air fuel mixture. An intake air throttle in one intake runner helps improve turbulence under low speed conditions 17

18 Intake Air Turbulence Intake Manifold Honda ictdi-2.2l diesel uses variable intake swirl for improved performance and reduced emissions 18

19 Air Intake Throttles Electric intake air throttles are used on many diesel having particulate filters. Restricting the air intake when needed will increase exhaust temperatures (less air dilution) Hotter exhaust temperatures are needed to regenerate the DPF 19

20 Air Intake Throttles EGR Valve Air Throttle 2008 Dodge Ram with a 6.7L Cummins diesel equipped with a DPF and N0x absorbing catalyst 20

21 Air Filters Filters come in a variety of shapes and types and are used primarily to remove dirt from intake air 21

22 Air Filters Air filters sieve dirt out of the intake air. Larger particles are removed first and then progressively smaller particles are removed. 22

23 Air Filters Filters clean better after they are in use for sometime! 23

24 Air Filters Pre-cleaner extend filter life by centrifugally spinning out dirt before it enters the filter 24

25 PowerCore Air Filters Ford Powerstroke PowerCore Filter PowerCore air filters use wall flow technology to trap and hold more dirt. They also occupy less under-hood space 25

26 Air Filter Restriction Air Filter Air Flow Air inlet restriction is measured in inches of water column not mercury. Best measured at full engine load peak torque 26

27 Air Filter Restriction A magnahelic gauge g is also used to measure air inlet restrictions 27

28 Problems Caused By Air Inlet Restrictions!!! Low turbocharger or intake boosts pressure. Higher exhaust temperatures caused by inadequate dilution of combustion gases by fresh air. Incomplete combustion due to poor contact between fuel and air. Lower fuel economy caused by poor combustion quality. Low power complaints caused by poor combustion quality. Visible exhaust emissions caused by poor combustion quality. Increased exhaust emissions caused by poor combustion quality. Shorter valve and piston life due to high heat loads in the cylinders caused by an absence of excess air. Increased lube oil use due to intake manifold vacuum drawing oil from intake valve guides and the turbocharger center housing then into the combustion chamber. 28

29 Air Supply & Emissions Without adequate air, emissions increase. This chart depicts emissions increase from a mechanically governed diesel engine used in a underground mining application 29

30 Restriction Gauges Restriction Gauge Electric Switch Mass Air Flow Sensor OBD-II vehicles require MAF sensor to detect problems with the air inlet system 30

31 Restriction Gauges Since diesels are sensitive to air restrictions, restriction gauges help the operator determine when a service for an air filter may be necessary 31

32 Blow-by Crankcase blow-by is produced from cylinder gases bypassing the piston rings. Blow-by needs to be vented from the crankcase or engine seals and gaskets will be pushed out by crankcase pressure causing oil leakage 32

33 Crankcase Blow-by Crankcase Blow-by Tube Blow-by Gas A blow-by or road draft tube is often used to vent crankcase blow-by gas. This 7.3 IDI Turbocharged engine has excessive blow-byby 33

34 Closed Crankcase Ventilation Air Inlet To Turbocharger Crankcase gases returned to air intake Closed crankcase ventilation systems returns blow-by back into the air intake. Open crankcase systems vents blow-byby to the atmosphere (7.3 Powerstroke) 34

35 Closed Crankcase Ventilation CDR Valve Diesels have little or no intake vacuum to draw gases into the engine. Closed crankcase ventilation systems may use crankcase depression regulators (CDR valves). Blow-by to Turbo Inlet CDR s prevent crankcase pressure from getting too low (from plugged air filters) and drawing dirt into the engine. CDR s also prevent crankcase pressure from becoming too high h 35

36 CDR Valves High Flow Low Flow Flow rate from a CDR valve is balanced between crankcase pressure and intake pressure. Negative crankcase pressure is limited to just a few inches of water column pressure 36

37 Closed Crankcase Ventilation Air Inlet To Turbocharger Oil seepage from crankcase gases in intake Crankcase blow-by contains significant quantity of oil mist/vapour. The vapour is classified as a particulate (PM) emissions 37

38 Open Crankcase Ventilation Oil Air Separator Air To Atmosphere Oil Drain To Crankcase 2007 emission standards do not permit crankcase blow-by to be vented directly to the atmosphere. Oil must be separated from the blow-by first. 38

39 Open Crankcase Ventilation & OBD-II OBD-II engines require monitoring of crankcase pressure e to detect problems associated with the closed crankcase ventilation system 39

40 Open Crankcase Ventilation Oil and air (produced from compression leakage past rings) is separated in the ventilation valve using a process called coalescence 40

41 Open Crankcase Ventilation The crankcase ventilation valve redirects oil to the engine sump and air to the road draft tube 41