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Engine Performance Systems

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Presentation on theme: "Engine Performance Systems"— Presentation transcript:

1 Engine Performance Systems
Chapter 24 Engine Performance Systems

2 Engine Performance Systems
Responsible for how the engine runs Complete combustion requires: Correct amount of air Correct amount of fuel Mixed in a sealed container Shocked with the correct amount of heat

3 Ignition Systems Supplies properly timed, high-voltage spark, under all operating conditions A six-cylinder engine at 4000 rpm requires 12,000 sparks per minute Distributor (DI) and distributor less (DIS) ignitions are two main types

4 Distributor Ignition

5 Electronic Ignition

6 Purpose of the Ignition System
Generate enough heat to ignite mixture Maintain the spark long enough for total combustion of the fuel Must deliver the spark to each cylinder to allow combustion to begin at the correct time

7 Ignition Timing For maximum power, combustion should be present when piston is at 10 to 23 degrees ATDC Engine speed At higher rpm timing must advance Engine load Light loads require timing advance Heavy loads require timing retard

8

9 Ignition Timing (Cont.)
Refers to the precise time spark occurs Referenced to the position of cylinder 1 in relation to crankshaft rotation

10 Firing Order To supply spark at the correct time, each cylinder fires in a specific order every 720 degrees

11 Knowledge Check Why must the spark timing begin earlier as engine speed increases? Spark timing must begin earlier as engine speed increases because the time to generate the spark is constant. As engine speed increases, the spark has to be delivered earlier to account for the decreased time available before the piston reaches TDC.

12 Computer Controlled Systems
Computerized ignition systems receive input from: Engine temperature, engine speed, manifold vacuum, throttle position, intake air temp, and other sensors This input is used to advance or retard timing as required

13 Fuel Systems Typical fuel supply system includes:
Fuel tank, lines, filter, and a pump A pressure regulator maintains system pressure The pressure generates the spraying force to inject the fuel

14 Fuel Injection Precise Reliable Cost effective
Electronic fuel injection systems are computer controlled

15 Fuel Injection - TBI

16 Fuel Injection - CPI

17 Fuel Injection - PFI

18 Fuel Injection - GDI

19 Air Induction System

20 Air-Fuel Mixtures Ideal ratio for most conditions is 14.7:1
Nearly 10,000 gallons of air mixed with one gallon of gasoline More air than ideal is called lean More fuel than ideal is called rich Power and efficiency require different ratios

21

22 Emission Control Systems
Reduce pollutants and environmentally damaging substances Smog irritates eyes, nose, and throat Formed when HC and NOx are exposed to sunlight

23 Emission Control Systems (Cont.)
Three main automotive pollutants: Hydrocarbons (HC) – largely from unburned fuel and gasoline evaporation Carbon Monoxide (CO) – results from incorrect air/fuel mixtures Oxides of Nitrogen (NOx) – caused by nitrogen and oxygen bonding at high temperatures Particulate emissions present in diesel exhaust

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25 Computer Controlled Systems
EGR valve Air pump Evaporative emissions canister The PCM keeps the three major pollutant levels low

26 Knowledge Check Technician A says an air-fuel ratio of 12:1 is a lean mixture. Technician B says an air-fuel ratio of 12:1 is a rich mixture. Who is correct? Technician B

27 Engine Control Systems
Primary engine control computer is the ECM or PCM Based on input, may command a change Monitors system activity for faults Linked to several other modules Share information on the CAN data bus

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29 System Components When making decisions, the PCM refers to three sources: Look-up tables - contains calibrations and specifications System strategy - learned adaptations Sensor input - determines necessary actions and if sensor data is valid

30 Computer Logic Decisions are made step-by-step
Determine engine operating mode Choose best strategy for present mode Determines the goal to be reached Determines how the goal can be achieved

31 Additional Engine Controls
Variable Valve Timing PCM controls a solenoid which controls oil into camshaft phasers Cylinder Deactivation PCM controls a solenoid which controls oil flow to lifters or rocker arms Electronic Throttle Control Motor driven throttle plate

32 Additional Engine Controls (Cont.)
Variable Intake Manifolds Two or more runners to match air flow with engine speed Control of Non-Engine Functions Air conditioning compressor clutch Torque converter clutch

33 VECI Decal Provides information about installed emission control devices

34 On-Board Diagnostic Systems
OBD I Phased in 1988 Most used flash codes DTC represented open, shorted, high resistance, or outside normal range faults Monitored a few systems and had limited DTCs Often required a specific scan tool

35 Flash Codes

36 OBD II Designed to ensure emissions remain as low as possible over life of vehicle Added monitor functions: Catalyst efficiency Engine misfire Evaporative system Secondary air system EGR flow rate

37 OBD II (Cont.) Basic data parameters and codes
Monitors effectiveness of emissions system Every part that affects emissions is checked MIL illuminated if emissions exceed 150% of allowable standard for that vehicle PCM uses EEPROM for updates

38 Data Link Connector (DLC)
Standardized Vehicles may have more than one DLC Must be located near steering column

39 OBD II Terms All manufacturers must use the same names and acronyms
All service information required to use new terms as of 1993

40 OBD II for Light-Duty Diesels
Mandated for all diesel engine vehicles weighing 14,000 pounds or less Very similar to gasoline system

41 OBD III Not implemented as yet
Aims to minimize the delay between emissions failure detection and the actual repair Mandates codes automatically read: May use cell phone reporting Roadside readers collect and transmit data Satellite data retrieval possible One time owner activated reporting

42 Knowledge Check What are three ways in which OBD II has standardized onboard computer systems? OBD II uses a standardized connector, standardized codes and data, and standardized component names.

43 System Operation Closed Loop Mode Open Loop Mode
PCM receives and processes information and adjusts outputs, resulting in new input data Open Loop Mode Used when the engine is cold PCM does not respond to feedback information Makes decisions based on programming

44 Fail Safe or Limp-In Mode
Used when a critical sensor is lost or out of normal range Uses fixed values in place of sensor data May generate a modified value based on input from other sensors

45 Adaptive Strategy Learns from past experience
May have short and long term strategies: Short term used immediately to overcome a change in operation Long term based on feedback about short term strategies Can adapt for wear

46 OBD II Monitoring Capabilities
Monitors to detect failing systems Illuminates the MIL before the failure Performs tests on subsystems Some monitors run continuously Other monitors only run under certain operating conditions, called enable criteria

47 OBD II Monitors

48 OBD II Drive Cycle

49 Catalyst Efficiency Monitor
Uses two oxygen sensors Converter stores oxygen when lean Efficiency is measured by oxygen storage

50 Misfire Monitor Unburned fuel enters exhaust Can destroy catalyst
Uses CKS sensor Most OBD II systems allow about 2% rate

51 Type A Misfires Checked for at 200-rpm increments
A misfire between 2% and 20% is excessive PCM may shut off fuel injector(s) If injector(s) not shut off, the MIL flashes If injector(s) are shut off, the MIL illuminates

52 Type B Misfires Checked over a 1000-rpm period
If misfire exceeds 2% to 3%, it is considered excessive May not damage catalyst but will increase emissions A pending DCT set MIL on if fault detected on second trip

53 Type C Misfires Can cause vehicle to fail emissions test
Not severe enough to damage catalyst or raise emissions over 1.5 FTP

54 Fuel System Monitoring
The PCM monitors and adjusts fuel delivery based on oxygen sensors feedback Short term fuel trim (STFT) makes minor injector pulse-width adjustments Long term fuel trim (LTFT) is set by the effectiveness of STFT The fuel trim monitor is continuous

55 Fuel Trim

56 Heated Oxygen Sensor Monitor
Rich to lean and lean to rich response times Report time of sensors gives an indication of heater circuit operation All HO2S monitored once per drive cycle The monitor will vary fuel delivery to check HO2S response

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58 HO2S Monitoring

59 EGR System Monitoring Some systems monitor EGR temperature
Other systems use the MAP sensor data Monitors EGR operation, flow rates, and opens and shorts in the circuit

60 Evaporative Emission System Monitor (EVAP)
Tests the ability of the fuel tank to hold pressure Also tests the systems ability to purge fumes from the charcoal canister

61 EVAP Monitoring

62 Enhanced EVAP Systems In use since 2003 Detects leaks and restrictions
Checks EVAP system integrity Performs a vacuum test Uses a special fuel filler cap Loose or missing filler cap will set an EVAP code

63 Secondary Air Injection (AIR) System Monitor
Can be tested by injecting air upstream of HO2S sensor Many systems inject air into exhaust manifold during open loop Air then injected into catalytic converter during closed loop

64 Thermostat Monitor 2002 and new vehicles
Checks for cooling system defects Monitors for preventing closed loop operation Checks time required for the cylinder head to reach a specific temperature

65 Thermostat Monitoring

66 PCV Monitor Vacuum leaks affect PCV operation
PCV removes HC from crankcase Monitors HO2S signals for consistent lean readings and the lack of switching

67

68 Variable Cam Timing Monitor
Checks VVT operation Monitors reaction time

69 Electronic Throttle Control Monitor
Monitored due to safety concerns System has redundant control and monitoring If a fault is detected, a reduced engine power mode is commanded

70 Comprehensive Component Monitor (CCM)
Continuous monitor Looks at any electronic input that could affect emissions Monitors sensor range values Checks frequency input rationality Monitors outputs by checking voltage

71 Knowledge Check Which OBD II monitor is responsible for verifying proper engine operating temperature? The thermostat monitor.

72 OBD II Self-Diagnostics
Not all problems will turn on MIL or set a DTC DTCs set for out of range signals but can be caused by other factors If not DTCs but there is a driveability issue, check basic engine and support systems

73 MIL Must illuminate if an emissions fault is detected
MIL may stay on or blink MIL may go back off but a DTC and freeze frame are stored If the fault is not detected for 40 key cycles, the DTC and freeze frame are erased

74 MIL (Cont.) Check MIL command with scan tool
The light may not work but MIL command will be displayed in scan data

75 OBD II Trouble Codes DTCs are standardized

76 Freeze Frame Data PCM takes a snapshot of activity when the MIL is illuminated Used by PCM for comparison of operating conditions if the same problem reoccurs Can be useful by technicians Erased if the DTC is erased

77 Freeze Frame Example

78 Test Modes All OBD II systems have same basic test modes accessible with an OBD II scan tool

79 Test Modes (Cont.) Mode 1 – parameter ID (PID) mode
Allows access to current data values, calculated values, and system status information Some PID values are manufacturer specific

80 Test Modes (Cont.) Mode 2 – freeze frame data access mode
Mode 3 – access to stored DTCs Mode 4 – PCM reset mode Resets all DTCs, freeze frames, DTC histories, monitor test results, and monitor status Mode 5 – O2 sensor monitoring test Actual O2 sensor outputs during test cycle Used for catalyst efficiency monitoring

81 Test Modes (Cont.) Mode 6 – hexadecimal data
Can be used for non-continuous system problem identification May misfire data Can be used to find pending problems

82 Test Modes (Cont.) Mode 7 – test results for continuous monitoring systems Mode 8 – bidirectional control request Mode 9 – vehicle information request

83 Knowledge Check Technician A says Mode 6 data is used to identify stored DTCs. Technician B says Mode 6 data can be used to identify possible pending concerns. Who is correct? Technician B

84 Basic Diagnosis of Electronic Engine Control Systems
What to test and why Logical diagnosis Start with most likely cause Work from most obvious solution first Check all non-electronic control possibilities

85 Repair Information DTC and freeze frame retrieval
No communication diagnosis TSBs Strategy chart for DTCs Parts locations Wiring diagrams Component test sequences

86

87 Diagnosing OBD II Systems
At least one drive cycle is required Scan tools show monitor status Readiness monitor tools available

88 Monitor Status

89 Troubleshooting OBD II Systems
Interview the customer Check the MIL Connect scan tool Check DTCs and freeze frames Check service history and information Visual inspection

90 Visual Inspection

91 Troubleshooting OBD II (Cont.)
Check DTCs and monitors Basic inspection DTC chart Check for intermittent problems Perform repairs Repair verification

92 Check DTCs

93 Intermittent Faults May not set DTC or light the MIL
Check history DTCs Evaluate symptoms and conditions Identify circuit or system that may be at fault Follow intermittent procedures in manual Visual inspection Test circuit wiring

94 Visual Inspection

95 Serial Data PIDs are codes used to request data from PCM
Scan tools request and receive serial data Scan tool PID requests information from a device on the network Many PIDs are standard but not all are supported by all manufacturers

96 PIDs

97 Using Mode 6 Stored monitor test result values
Provided with $, TIDs and CIDs Hexadecimal code Can be used to identify problems when a DTC is not retrieved Compare stored value to normal value

98 Mode 6

99 Repairing the System Do not connect accessories to OBD II circuit
Do not move or alter grounds Use exact relay replacements Ensure proper connections Torque ground fasteners to specifications

100 Diagnosing OBD I Systems
Limited self-diagnostic capability Hard faults (on-demand) occur at time of self-test Intermittent faults not present at self-test can store a DTC for a number of key cycles Several different methods to access DTCs Perform a thorough visual inspection

101 Unlocking OBD I Trouble Codes
Scan tools can be used on many, including most GM, Ford and Chrysler products Many imports use a flashing LED or check engine light Codes displayed when a connector is jumpered or PCM placed into diagnostic mode

102 Nissan Diagnostic Mode

103 Knowledge Check How may reading DTCs differ on OBD I vehicles compared to OBD II vehicles? OBD I vehicles may not have a diagnostic connector, there are no standardized diagnostic connectors or codes, codes may be ready by watching a blinking LED or MIL or with a scan tool.


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