Delphi Multec 3.5 Applications Manual
Multec 3.5 Top Feed Fuel Injector
Application Manual
Fuel Systems Applications Engineering
Delphi Energy & Chassis Systems
5500 W. Henrietta Rd.
P.O. Box 20366
Rochester, New York 14602 USA
Delphi Energy and Chassis Systems 2005
Multec 3.5 Fuel Injector Application Manual Revision Summary
Multec 3.5 Top Feed Fuel Injector Application Manual
Release/Revision Summary Sheet
CHANGE NO. DATE REASON FOR CHANGE PAGE(S)
Issued April 2004 N/A N/A
1 July 2005 Replaced “J-spray…” with “J-2715 (Draft)” in section
1.9.4.2
1 Nov. 05 Added shutdown throttle closure note to section 8.4.4 8-4
1 Changed ‘and applicable’ to ‘any applicable’ in
section 1.9.1
1 Nov 05 Added reference to Worldwide Emissions Standards
booklet to section 2.2.3 and 1.9.3
1 Nov 05 Updated MTBE phase out plans in section 2.2.6.2 2-10
1 Nov 05 Updated gasoline sulfur requirements in section
2.2.6.3.4
1 Nov 05 Re-worded section 2.2.7.3 for clarity 2-18
1 Nov 05 Corrected return and inlet locations in Figure 2-5 2-23
1 Nov 05 Added extended tip description to section 3.2.2 and
view to Figure 3-2
1 Nov 05 Changed “core” to “valve” in section 3.2 3-1
1 Nov 05 Added rotational orientation note to section 3.3.5 3-6
1 Nov 05 Reworded section 3.5.1 for clarity 3-11
1 Nov 05 Added Zener diode voltage range and injector flow
test for vehicle calibration note to section 3.6.3
1 Nov 05 Revised calculation example from max flow to min
flow in section 3.7
1 Nov 05 Added J-2715 to section 3.8 3-21
1 Nov 05 Revised 96% spray volume for dual spray to 90% in
section 3.8.2
1 Nov 05 Updated Figure 3-12 to current data format 3-26
1 Nov 05 Removed word “serviceable” from filter requirements
in section 3.12
1 Nov 05 Changed “Component Technical Specification” to
“Engineering Product Specification” in section 3.16
1 Nov 05 Added “absolute” to manifold air pressure in Table
3-2
1 Nov 05 Revised Figure 6-1 to include o-ring installation tool 6-3
1 Nov 05 Added section 6.4 and Figure 6-2 – injector
installation into fuel rail and renumbered remaining
sections
1 Nov 05 Added reference to Figure 6-1 in section 4.3 4-8
1 Nov 05 Added “total” to A/F variation” in section 3.10.2 3-33
1 Nov 05 Added section 5.2.3.3 “Variable Fuel Pressure
Compensation”. Renumbered remaining sections.
1 Nov 05 Added reference to terminal lubricant (section 7.5) in
Table 6-1
1 Nov 05 Added reference to terminal lubricant (section 7.5) in
section 4.4.4
1 Nov 05 Added reference to Figure 6-1 in section 6.5 6-6
1 Nov 05 Added metal fuel line recommendation to section
7.3.5
1-7
1-5
1-6, 2-8
2-12
3-3, 3-4
3-13
3-19
3-22
3-36
3-39
3-40
6-4
5-10
6-2
4-14
7-5
Delphi Energy and Chassis Systems
Revision: 11/05-1
Multec 3.5 Fuel Injector Application Manual Revision Summary
1 Nov 05 Renumbered pages in section 4 starting at 1 4-1
1 Nov 05 Changed dwell time from 1 hr to 0.5 hr and duration
9-3
from 240 hours to 120 hours in section 9.3.2.1
Delphi Energy and Chassis Systems
Revision: 11/05-01
Multec 3.5 Fuel Injector Application Manual Table of Contents
Table of Contents
1. 0 INTRODUCTION ................................................................................1-1
1.1 SCOPE OF DOCUMENT .....................................................................................................................1-1
1.2 CLASSIFICATION .............................................................................................................................. 1-1
1.3 DOCUMENT MANAGEMENT ............................................................................................................... 1-1
1.3.1 Document Release and Updates .........................................................................................1-1
1.4 COMMERCIAL CONSIDERATIONS .......................................................................................................1-1
1.5 OBJECTIVES OF THIS MANUAL .......................................................................................................... 1-1
1.6 HOW THIS MANUAL IS ARRANGED..................................................................................................... 1-2
1.7 CONVENTIONS USED IN THIS MANUAL............................................................................................... 1-4
1.8 HYPERLINKS....................................................................................................................................1-5
1.9 APPLICABLE DOCUMENTS ................................................................................................................1-5
1.9.1 Order of Precedence ............................................................................................................ 1-5
1.9.2 Government Documents ......................................................................................................1-5
1.9.3 Other Delphi Reference Documents ....................................................................................1-5
1.9.4 Industry Documents .............................................................................................................1-6
1.9.5 Useful Web Sites..................................................................................................................1-6
2. 0 FUNDAMENTALS .............................................................................. 2-1
2.1 GENERAL ........................................................................................................................................2-1
2.2 ENGINE COMBUSTION FUNDAMENTALS ............................................................................................. 2-2
2.2.1 Air/Fuel Ratio Effects on Combustion ..................................................................................2-3
2.2.2 Fuel Atomization................................................................................................................... 2-7
2.2.3 Fuel Spray Characteristics and Injection Timing.................................................................. 2-8
2.2.4 Benefits of Electronic Fuel Injection Over Other Types of Fuel Systems ............................2-9
2.2.5 Impact of Transient Conditions on Combustion ................................................................... 2-9
2.2.6 Impact of Fuel Composition................................................................................................2-10
2.2.7 Engine-Vehicle Environment..............................................................................................2-14
2.2.8 Maximum Power Fueling Requirements ............................................................................2-19
2.2.9 Injector Flow Tolerances ....................................................................................................2-20
2.3 FUEL FLOW CONSIDERATIONS........................................................................................................2-20
2.3.1 Minimum Fuel Pump Flow Output......................................................................................2-21
2.3.2 Nominal Fuel Pump Output ................................................................................................ 2-21
2.3.3 Fuel Pump Check Valve Requirements .............................................................................2-22
2.3.4 Pressure Regulator Gain/Considerations (Vacuum Biased).............................................. 2-22
2.4 IMPACT OF EMISSIONS REQUIREMENTS .......................................................................................... 2-23
2.4.1 The Impact of Emission Requirements on Fuel Control Systems .....................................2-23
2.4.2 Fuel Injector Design Effects on Evaporative Emissions.....................................................2-25
2.4.3 Impact of Canister Purge on Engine Fueling .....................................................................2-26
2.4.4 Impact of EGR and PCV on engine fueling........................................................................ 2-27
2.4.5 Injector Flow Characterization............................................................................................ 2-27
3. 0 PRODUCT DESCRIPTION.................................................................3-1
3.1 SCOPE............................................................................................................................................3-1
3.2 GENERAL DESCRIPTION ...................................................................................................................3-1
3.2.1 Appearance .......................................................................................................................... 3-3
3.2.2 Exterior Outline..................................................................................................................... 3-3
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Table of Contents Multec 3.5 Fuel Injector Application Manual
3.2.3
Usage Definition ................................................................................................................... 3-3
3.2.4 Failure Diagnostics...............................................................................................................3-3
3.3 PHYSICAL SPECIFICATIONS ..............................................................................................................3-3
3.3.1 Dimensions........................................................................................................................... 3-3
3.3.2 Mass ..................................................................................................................................... 3-5
3.3.3 Identification and Markings ..................................................................................................3-5
3.3.4 Internal Components ............................................................................................................ 3-5
3.3.5 Injector Retaining Clip ..........................................................................................................3-6
3.3.6 Seal rings..............................................................................................................................3-7
3.4 CUSHION SEAL INJECTOR DESIGN ....................................................................................................3-8
3.5 INJECTOR DESIGN ...........................................................................................................................3-8
3.5.1 Dual Spray Fuel Injector.....................................................................................................3-11
3.6 INJECTOR CONTROLS – CONTROLLER DRIVE CIRCUIT ..................................................................... 3-12
3.6.1 Minimum Operating Voltage (MOV) ................................................................................... 3-12
3.6.2 Driver Considerations.........................................................................................................3-12
3.6.3 Driver Circuit Clamping Voltage ......................................................................................... 3-13
3.6.4 Injector Polarity................................................................................................................... 3-13
3.7 INJECTOR FLOW RATE SIZING ........................................................................................................3-13
3.8 INJECTOR TARGETING, PLACEMENT AND CONE ANGLE....................................................................3-21
3.8.1 Targeting ............................................................................................................................3-21
3.8.2 Cone Angle......................................................................................................................... 3-22
3.8.3 Spray Atomization ..............................................................................................................3-23
3.9 PULSE-WIDTH LIMITS .................................................................................................................... 3-27
3.9.1 Minimum Pulse-Width (MPW) ............................................................................................ 3-28
3.9.2 Tailbiting .............................................................................................................................3-30
3.10 LINEAR AND WORKING FLOW RANGE ..................................................................................... 3-31
3.10.1 Linear Range......................................................................................................................3-31
3.10.2 Working Flow Range .......................................................................................................... 3-33
3.11 TIP LEAKAGE ........................................................................................................................3-34
3.11.1 Total Fuel System Tip Leakage Monte Carlo Analysis ......................................................3-35
3.12 CONTAMINATION RESISTANCE ............................................................................................... 3-36
3.13 DYNAMIC AND STATIC FUEL FLOW SPECIFICATIONS................................................................ 3-36
3.13.1 Flow Test Fluid Specification .............................................................................................3-37
3.14 NOISE ..................................................................................................................................3-38
3.15 ELECTRICAL SPECIFICATIONS ................................................................................................3-38
3.15.1 Solenoid Coil Specifications...............................................................................................3-38
3.15.2 Avalanche Energy ..............................................................................................................3-38
3.16 ENVIRONMENTAL CONDITIONS...............................................................................................3-39
3.16.1 Hot Fuel Handling...............................................................................................................3-39
3.16.2 Environmental Exposure ....................................................................................................3-40
4. 0 SYSTEM INTERFACE........................................................................4-1
4.1 GENERAL ........................................................................................................................................4-1
4.1.1 Interface Control Document .................................................................................................4-2
4.2 MECHANICAL INTERFACES ............................................................................................................... 4-3
4.2.1 Locating the Fuel Injector .....................................................................................................4-3
4.2.2 Orienting the Injector ............................................................................................................ 4-4
4.2.3 Vibration Levels....................................................................................................................4-5
4.2.4 Fuel Supply System Interface ..............................................................................................4-7
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Multec 3.5 Fuel Injector Application Manual Table of Contents
4.3 SEAL RINGS.....................................................................................................................................4-8
4.4 ELECTRICAL INTERFACE................................................................................................................... 4-9
4.4.1 Electromagnetic Compatibility..............................................................................................4-9
4.4.2 Wire Routing......................................................................................................................... 4-9
4.4.3 Fuel Injector Polarity........................................................................................................... 4-10
4.4.4 Fuel Injector Connector ...................................................................................................... 4-11
4.4.5 Controller............................................................................................................................4-14
5. 0 SOFTWARE .......................................................................................5-1
5.1 GENERAL ........................................................................................................................................5-1
5.2 CONTROL ALGORITHMS ................................................................................................................... 5-2
5.2.1 Injection Methods .................................................................................................................5-2
5.2.2 Open Loop Injector and Fuel Rail Characterization ............................................................. 5-4
5.2.3 Open-Loop Characterization ................................................................................................ 5-9
5.2.4 Closed-Loop Corrections ...................................................................................................5-14
5.2.5 Fuel Injection Timing ..........................................................................................................5-15
5.3 DIAGNOSTICS ................................................................................................................................5-17
5.3.1 Fuel Trim Diagnostics......................................................................................................... 5-17
5.3.2 Oxygen Sensor Diagnostics...............................................................................................5-18
5.3.3 Catalytic Converter Diagnostics ......................................................................................... 5-18
5.3.4 Injector Driver Diagnostics .................................................................................................5-18
5.3.5 Engine Misfire Diagnostics.................................................................................................5-18
5.3.6 Factors Affecting Engine Diagnostics ................................................................................5-19
6. 0 PRODUCT HANDLING ......................................................................6-1
6.1 PACKING PROCEDURES ...................................................................................................................6-3
6.2 RECEIVING AND STORAGE................................................................................................................ 6-4
6.3 MOVEMENT WITHIN THE PLANT ........................................................................................................ 6-4
6.4 INSTALLATION IN FUEL RAIL ............................................................................................................. 6-4
6.5 INSTALLATION ON THE ENGINE..........................................................................................................6-5
6.6 COMPONENT ASSEMBLY BEST PRACTICES ....................................................................................... 6-8
6.7 MAINTENANCE, SERVICE AND REPAIR .............................................................................................. 6-9
6.7.1 Diagnosing Malfunction Codes ............................................................................................6-9
6.7.2 Replacement Techniques ....................................................................................................6-9
6.7.3 Adjustments........................................................................................................................ 6-11
6.7.4 Interchangeability ...............................................................................................................6-11
6.8 SUPPORT OF COMPONENT AFTER SALE..........................................................................................6-11
7. 0 RECOMMENDATIONS AND PRECAUTIONS...................................7-1
7.1 TEMPERATURE ................................................................................................................................7-1
7.2 DURABILITY.....................................................................................................................................7-2
7.2.1 Injector Characteristics.........................................................................................................7-3
7.3 WEAR AND CONTAMINATION ............................................................................................................ 7-3
7.3.1 Internal Corrosion.................................................................................................................7-3
7.3.2 External Exposure ................................................................................................................ 7-3
7.3.3 Plugging................................................................................................................................7-4
7.3.4 Contamination Resistance ...................................................................................................7-4
7.3.5 Fuel System Generated Contamination ............................................................................... 7-5
7.3.6 Maximum Fuel Pressure ......................................................................................................7-5
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Table of Contents Multec 3.5 Fuel Injector Application Manual
7.3.7
Injector Storage .................................................................................................................... 7-5
7.4 PREVENTING ENGINE HYDRO-LOCK ..................................................................................................7-6
7.4.1 Engine Prime Pulse at Start .................................................................................................7-6
7.4.2 Vehicle Assembly Fuel System Prime .................................................................................7-7
7.5 INJECTOR HARNESS CONNECTOR – CORROSION ..............................................................................7-7
8. 0 TESTING RECOMMENDATIONS AND PRECAUTIONS ..................8-1
8.1 DYNAMOMETER TESTING .................................................................................................................8-1
8.1.1 Cylinder-to-Cylinder Distribution ..........................................................................................8-1
8.2 DURABILITY TESTING ....................................................................................................................... 8-1
8.3 DYNAMIC VEHICLE TESTING ............................................................................................................. 8-2
8.4 STANDARD VEHICLE DEVELOPMENT TESTS.......................................................................................8-2
8.4.1 Hot Fuel Handling................................................................................................................. 8-2
8.4.2 Spray Effect on Emissions ...................................................................................................8-3
8.4.3 Cold Driveability and Startability ..........................................................................................8-3
8.4.4 Crank vs. Leak .....................................................................................................................8-4
8.4.5 Altitude Driveability and Emissions ...................................................................................... 8-4
8.4.6 Low Pulse-Width Fueling Accuracy...................................................................................... 8-4
8.4.7 Driveability Index Fuel Sensitivity......................................................................................... 8-4
8.4.8 Spark Plug Fouling Tests .....................................................................................................8-5
8.4.9 Voltage Sensitivity ................................................................................................................ 8-5
8.4.10 Manifold Pressure Sensitivity ............................................................................................... 8-5
8.4.11 Standard Durability Tests .....................................................................................................8-5
8.4.12 Icing Tests ............................................................................................................................ 8-5
8.4.13 Production Limit Verification Tests....................................................................................... 8-5
9. 0 VALIDATION REQUIREMENTS ........................................................9-1
9.1 GENERAL ........................................................................................................................................9-1
9.2 VALIDATION TESTS ..........................................................................................................................9-1
9.2.1 Preliminary Physical Analysis .............................................................................................. 9-2
9.3 ENVIRONMENTAL EXPOSURE............................................................................................................ 9-2
9.3.1 External Corrosion................................................................................................................9-2
9.3.2 Temperature.........................................................................................................................9-3
9.3.3 Life Cycling ...........................................................................................................................9-3
9.3.4 Mechanical Integrity .............................................................................................................9-4
9.3.5 Overpressurization ...............................................................................................................9-5
9.3.6 Over-voltage.........................................................................................................................9-5
9.3.7 Injector Noise .......................................................................................................................9-6
9.3.8 Note on Additional Exposures..............................................................................................9-6
9.4 VERIFICATION................................................................................................................................. 9-6
10. 0 APPENDIX......................................................................................10-1
10.1 INTRODUCTION. ....................................................................................................................10-1
10.2 MULTEC 3.5 FUEL INJECTOR SYSTEM CUSTOMER COMPONENT CHECKLIST ............................ 10-2
10.3 COMPONENT APPLICATION CHECKLIST ..................................................................................10-8
10.4 COMPONENT ASSEMBLY BEST PRACTICES........................................................................... 10-12
10.5 GLOSSARY OF TERMS AND ABBREVIATIONS..........................................................................10-17
11. 0 INDEX.............................................................................................11-3
iv Delphi Energy and Chassis Systems
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Multec 3.5 Fuel Injector Application Manual Table of Contents
Tables
Table 2-1 - Stoichiometry of Alternate Fuel Blends .................................................................................2-4
Table 3-1 Solenoid Electrical Properties................................................................................................ 3-39
Table 3-2 - Injector Environmental Operating Conditions...................................................................... 3-39
Table 6-1 – Multec 3.5 Injector Handling ................................................................................................. 6-2
Table 6-2 - Recommended seal ring lubricants.......................................................................................6-8
Table 8-1 - Injector tip soak temperature vs required fuel pressure........................................................8-3
Table 9-1 - Potential Injector Test Fuels..................................................................................................9-4
Table 9-2 - Injector Verification Matrix Template ..................................................................................... 9-7
Figures
Figure 2-1- Engine Fuel System (shown is a demand fuel rail for a V6 application)............................... 2-2
Figure 2-2 - Air Fuel Ratio Effect on Catalytic Converter Efficiency ........................................................ 2-6
Figure 2-3 - Fuel Distillation Curve vs Temperature..............................................................................2-13
Figure 2-4 - 50% Vapor / Liquid Ratio vs RVP, Fuel and Pressure.......................................................2-17
Figure 2-5 - Fuel Pressure Regulator and Gain Calculation.................................................................. 2-23
Figure 2-6 - Engine Management System Open Loop vs Closed Loop System Architecture............... 2-24
Figure 2-7 - Catalytic Converter Efficiency vs Air/Fuel Ratio................................................................. 2-24
Figure 2-8 California Tailpipe Emissions Limits.....................................................................................2-25
Figure 2-9 - Evaporative Emissions Regulations..................................................................................2-26
Figure 3-1 - Top Feed Port Fuel Injection................................................................................................3-2
Figure 3-2 - Multec 3.5 Fuel Injector Dimensions – Seal ring design. (For exact dimensions, refer to
Delphi Injector Outline Drawing).......................................................................................................3-4
Figure 3-3 – Multec 3.5 Fuel Injector Dimensions – Cushion seal / Face seal design (For exact
dimensions, refer to Delphi Injector Outline Drawing. ...................................................................... 3-4
Figure 3-4 - Injector Identification and Markings......................................................................................3-5
Figure 3-5 Multec 3.5 Internal Components ............................................................................................3-6
Figure 3-6 -Injector Retaining Clip Designs ............................................................................................. 3-7
Figure 3-7 - Multec 3.5 Magnetic Circuit................................................................................................3-10
Figure 3-8 - Multec 3.5 Fuel Flow Path.................................................................................................. 3-10
Figure 3-9 - Dual Spray Injector.............................................................................................................3-11
Figure 3-10 - Injector Targeting .............................................................................................................3-21
Figure 3-11 - Dual Spray Injector Separation and Orientation Angle .................................................... 3-25
Figure 3-12 - Sample Single and Dual Spray Injector Patternator Results ........................................... 3-26
Figure 3-13 Injector Opening and Closing Response............................................................................ 3-27
Figure 3-14 - High Pulse-Width Flow Effects. Static Occurs at 10 msec (rep. rate = 10 msec)...........3-29
Figure 3-15 - Low Pulse-Width Flow Effects. (Rep. rate = 10msec) ...................................................3-29
Figure 3-16 - Injector Flow Curve Tailbiting...........................................................................................3-31
Figure 3-17 - Linear Range....................................................................................................................3-32
Figure 3-18 - Injector Working Flow Range ........................................................................................... 3-34
Figure 3-19 Fuel Rail Total Tip Leak Monte Carlo Simulation Example (4 cylinder)............................3-36
Figure 4-1 - Block Diagram ...................................................................................................................... 4-1
Figure 4-2 - Example of Recommended Mounting Feature Dimensions ................................................4-4
Figure 4-3 - Example of data presentation for steady state rpm. ............................................................4-7
Figure 4-4 - Typical Spectral Map............................................................................................................4-7
Figure 4-5 Injector Connector Polarity '+'..............................................................................................4-10
Figure 4-6 - Injector Electrical Connectors ............................................................................................4-11
Figure 4-7 - Metri-Pack Harness Connector ..........................................................................................4-12
Figure 4-8 - USCAR Harness Connector...............................................................................................4-13
Figure 4-9 - Electrical schematic of saturated switch injector driver circuit ........................................... 4-15
Figure 4-10 - Oscilloscope trace of injector avalanche energy measurement ......................................4-16
Figure 5-1 - Injector Firing Schemes (red bar = injection event) .............................................................5-4
Figure 5-2 - Slope and intercept graph (Flow vs. Pulse Width) ............................................................... 5-5
Figure 5-3 - Sequential injection timing considerations (4500 rpm) ......................................................5-16
Figure 6-1 Injector Seal Ring Installation Precaution .............................................................................6-3
Delphi Energy and Chassis Systems
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Table of Contents Multec 3.5 Fuel Injector Application Manual
Figure 6-2 Injector Installation Surface .................................................................................................... 6-5
Figure 7-1 - Thermocoupled injector........................................................................................................ 7-2
vi Delphi Energy and Chassis Systems
Revision: 11/05-01
Multec 3.5 Fuel Injector Application Manual Introduction
1.0 Introduction
1.1 Scope of Document
This Application Manual communicates Multec 3.5 Top Feed Port Fuel
Injector application guidelines for spark ignition engines.
1.2 Classification
The information and specifications in this manual covers Multec 3.5
gasoline fuel injectors.
1.3 Document Management
This document shall be maintained by Delphi. Express written consent of
Delphi must be obtained before any use or modification of this document
is permitted.
1.3.1 Document Release and Updates
The information contained in this manual is accurate and current as of the
date of publication. As changes occur that update the content of the
manual a new manual revision shall be released. All updates shall be
issued and distributed by Delphi-E&C electronically. The latest revision
shall be uploaded to an Applications Engineering website for access
throughout Delphi. http://hal.roc.acr.gmeds.com/applications/
1.4 Commercial Considerations
All commercial considerations/cost and scheduling requirements shall be
handled by the Delphi Sales and Marketing Group.
1.5 Objectives of this Manual
Delphi provides advanced fuel systems technology for both automotive
and non-automotive applications. The Multec 3.5 Fuel Injector is an
example of Delphi leadership and its commitment to continuous
improvement and world-class quality.
This Multec 3.5 Fuel Injector Application Manual has been developed to
support the efforts to integrate the Multec 3.5 Fuel Injector into a specific
fuel system or engine management system.
Delphi Energy Chassis Systems Revision: 11/05-1 1-1
Introduction Multec 3.5 Fuel Injector Application Manual
The objectives of this document are to help:
• Obtain maximum value and optimum performance from the Multec
3.5 Fuel Injector
• Integrate the Multec 3.5 Fuel Injector within the engine control system
(hardware and software)
• Protect the Multec 3.5 Fuel Injector from damage caused by improper
usage, mounting, handling, or installation
• Prevent testing errors that might result in an inaccurate evaluation of
Multec 3.5 Fuel Injector performance
• Prevent calibration errors that may interfere with the proper operation
of the Multec 3.5 Fuel Injector
To accomplish these objectives, this manual provides the following:
• A description of the components and features of the Multec 3.5 Fuel
Injector
• A description of the process used to determine the requirements
needed to achieve the following objectives:
− Accurate fuel flow requirements
− Proper injector spray
− Proper injector spray targeting
• A description of the options for packaging and mounting, as well as the
optional features available to meet underhood packaging, serviceability
and diagnostic requirements
• Calibration and testing guidelines
• A checklist of interface details required for Delphi to ensure that the
proper fuel injector selection is made to meet customer requirements.
The fuel injector should be specified based upon the constraints/
demands of the engine control module (engine controller and software)
and the chassis fuel supply subsystem (fuel rail, fuel pressure regulator,
fuel pump, fuel filter and supply lines).
1.6 How this Manual is Arranged
An overview of each section in this manual is provided below.
1-2 Delphi Energy and Chassis Systems
Revision: 11/05-01
Multec 3.5 Fuel Injector Application Manual Introduction
Section 1.0 — Introduction
Section 1.0 provides an overview of the scope, objectives, and format of
this manual and lists documents on which it is based. The documents
listed in section 1.9 can be referred to for additional detail to aid in
understanding the requirements set forth in this manual.
Section 2.0 — Injector Fundamentals
Section 2.0 describes the characteristics and requirements of the Multec
3.5 Fuel Injector and its related components. Also discussed is an
overview of combustion fundamentals with a detailed description of how
the fuel system works together with the air/fuel delivery system and
exhaust gas treatment to meet vehicle emissions requirements.
Section 3.0 — Product Description
Section 3.0 provides an overview of fuel injector construction, materials,
performance and cost drivers. Physical and electrical specifications for
standard assemblies are defined and flow and performance specifications
for commonly available fuel injectors are provided. Also discussed is the
process Delphi uses to provide custom products.
Section 4.0 — System Interface – Hardware & Electrical
Section 4.0 describes and illustrates the mechanical and electrical
interfaces required to obtain optimum performance from the fuel injector.
The electrical interface, chassis fuel supply and fuel filtration interface are
also described.
Section 5.0 — System Interface – Software Controls
Section 5.0 provides both an overview and specific detail on the software
requirements to operate the fuel injector. Various control algorithms
commonly used to achieve optimum performance under varying engine
conditions are described, and additional algorithms, which are based on
emissions and driveability requirements, are recommended. Calibration
and diagnostics are also discussed. Understanding this section is critical
to achieving optimum performance from the Multec 3.5 Fuel Injector.
Section 6.0 — Product Handling
Section 6.0 presents Delphi recommendations for the handling, storage,
installation, and servicing of the fuel injector. Proper handling of the
product, from the time it arrives on the receiving dock until it is installed
in the vehicle, reduces the risk of accidental damage and helps ensure that
the fuel injector will function as intended.
Delphi Energy Chassis Systems Revision: 11/05-1 1-3
Introduction Multec 3.5 Fuel Injector Application Manual
Section 7.0 — Recommendations and Precautions
Section 7.0 provides a summary of Delphi recommendations and
precautions for proper fuel injector use. Common misuses are identified
and alternate solutions presented.
Section 8.0 — Testing Procedures
Section 8.0 discusses testing procedures that are based on the experience
of Delphi and its customers. Adhering to the recommendations contained
in this section will ensure that the fuel injector is evaluated correctly under
conditions that parallel normal use and operation.
Section 9.0 — Validation Requirements
Section 9.0 outlines the process for validating the fuel injector, i.e.,
ensuring that it meets specified quality, reliability, and durability goals
and conforms to governmental standards/regulations.
Section 10 - Appendix
10.1— Introduction
10.2— Injector/ System Component Checklist
10.3— Multec 3.5 Injector Application Guideline Checklist
10.4— Component Assembly Best Practices
10.5— Glossary of Terms and Abbreviations
Section 11.0 — Index
1.7 Conventions Used in this Manual
The pages in this manual are formatted with a wide left margin. The
purpose of this format is to help locate important topics throughout the
document. The left margin contains additional information:
• key words and information to which special attention must be paid.
Other important information is shown in italic type and is preceded with
the boldface word NOTE, CAUTION, or WARNING.
•
Note—Indicates important technical detail that is relevant to the topic
being discussed.
•
Caution —Indicates information about a condition or an activity that
must be performed to prevent damage to the Multec 3.5 Fuel Injector,
fuel system, electronic control system, engine or the vehicle.
•
Warning —Indicates a condition that might pose a risk to personal
safety.
1-4 Delphi Energy and Chassis Systems
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Multec 3.5 Fuel Injector Application Manual Introduction
Note: Unless otherwise noted, the numbered figures displayed in this
manual are illustrations, not technical drawings. As such, these
illustrations may not reflect actual dimensions. All final critical
dimensions should be confirmed on part prints.
1.8 Hyperlinks
All references to section numbers, figures and tables are hyperlinks that
will jump to the section of the document containing the reference when
the mouse is left clicked over the reference number. (Applies only to
WORD version of the applications manual.)
1.9 Applicable Documents
1.9.1 Order of Precedence
When there appears to be a contradiction between this application manual
and an outline drawing or other document, the conflict must be formally
resolved through the Delphi application engineer. Until the contradiction
can be resolved, the part outline drawing will always take precedence.
Nothing in this document shall be considered to supersede any applicable
law or regulation unless a specific exemption has been obtained.
1.9.2 Government Documents
To be supplied by customer for specific country.
1.9.3 Other Delphi Reference Documents
1.9.3.1 Multec 3.5 Fuel Injector specific Part Number and associated outline drawing
1.9.3.2 Multec 3.5 Fuel Injector Component Technical Specification (or equivalent document) if
available
1.9.3.3 Delphi Fuel Rail Applications Manual
1.9.3.4 Delphi Catalytic Converter Applications Manual
1.9.3.5 Delphi Fuel Pump Applications Manual
1.9.3.6 Delphi EGR Applications Manual
1.9.3.7 SFMEA
1.9.3.8 OBD-II Diagnostic Procedures
1.9.3.9 Delphi Worldwide Emissions Standards summary booklet
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Introduction Multec 3.5 Fuel Injector Application Manual
1.9.4 Industry Documents
1.9.4.1 SAE Standard Procedure J1832
1.9.4.2 SAE J-2715 (Draft) Gasoline Fuel Injector Spray Measurements and Characterizations
1.9.4.3 ASTM D86, “Standard Test Method for Distillation of Petroleum Products at Atmospheric
Pressure”
1.9.4.4 ASTM D2533, “Standard Test Method for Vapor-Liquid Ratio of Spark-Ignition Engine
Fuels”
1.9.4.5 ASTM D4814, “Standard Specification for Automotive Spark-Ignition Engine Fuel”
1.9.4.6 ASTM D5191, “Standard Test Method for Vapor Pressure of Petroleum Products (Mini
Method)”
1.9.4.7 World Wide Fuel Charter
1.9.4.8 Internal Combustion Engine Fundamentals. John B. Heywood, McGraw-Hill Publishing,
1988.
1.9.5 Useful Web Sites
1.9.5.1 EPA Vehicle Emissions Information:
http://www.epa.gov/ebtpages/airmobilevehicleemissions.html
1.9.5.2 CARB Web Site: http://www.arb.ca.gov/
1.9.5.3 Delphi Corp Web Site:
http://www.delphi.com/
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2.0 Fundamentals
2.1 General
The Multec 3.5 Fuel Injector is a component of the Air/Fuel Subsystem.
The function of the fuel injector is to provide the required fuel quantity
and spray geometry to the each engine cylinder to meet vehicle
performance and emissions requirements over a wide range of operating
conditions. The Multec 3.5 Fuel Injector is designed for electronic port
fuel injection systems, which maintain an individual fuel injector for each
engine cylinder and operate the individual injectors via an electrical
signal. The control logic for each injector is typically governed through an
electrical control module that is provided by the customer. The customer
develops the logic with input from Delphi.
The fuel injector supply system typically consists of the fuel injectors, a
fuel rail or conduit, a fuel pressure regulator and connections to fuel
supply and return lines. This portion of the fuel system is installed directly
to the intake system of the engine. On some applications, especially
returnless fuel systems, a mechanical device for damping fuel pressure
pulsations may be incorporated to reduce fuel line "hammer". Returnless
fuel systems do not have a return line connection and typically incorporate
the pressure regulator either closer to or within the fuel supply tank. (See
Fuel Rail Applications Manual for more details.)
The vehicle fuel system includes the above mentioned injector supply
system as well as fuel supply and return (optional) lines, fuel filter, fuel
pump and fuel tank. The evaporative emissions system, while not directly
linked to the fuel injector supply system, must be considered, as vapor
purge from this system into the engine intake system will directly impact
how the fuel injector is controlled under certain conditions.
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Fuel Rail
Injector Clip
Multec 3.5
Fuel Injector
Figure 2-1- Engine Fuel System (shown is a demand fuel rail for a V6 application)
2.2 Engine Combustion Fundamentals
Internal combustion is a complex process involving interactions of many
engine subsystems over widely changing conditions. A complete
explanation of these interactions and requirements and the theory of
combustion are outside the scope of this manual. The following subsections summarize the major considerations involved with the fuel
injector’s impact on combustion. If a more detailed explanation is
required on any of these topics, please contact Delphi Energy and Chassis
Systems.
Manifold Seal
The following text is suggested for those who would like a more
comprehensive understanding of internal combustion engine operation and
theory:
Internal Combustion Engine Fundamentals. John B. Heywood,
McGraw-Hill Publishing, 1988.
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2.2.1 Air/Fuel Ratio Effects on Combustion
The goal of the Multec 3.5 Fuel Injector is to supply the correct fuel mass
to achieve the correct air/fuel ratio (A/F). Complete combustion will
depend, in general, on the following:
• The air and fuel must be in the proper portions (referred to as the
stoichiometric mixture or ratio); this proportion will depend upon the
chemistry of the fuel.
Ref. Sec 2.2.1.1
Ref Sec. 2.2.7.2 & 8.4.1
Note
Note: Stoichiometric A/F refers to the quantitatively derived ratio of air
to fuel that will allow the chemical process of combustion to be delivered
to ideal equilibrium. In this manual, A/F is stated in terms of their
molecular weights – that is, molecular weight of air over molecular
weight of fuel.
• The mixture must be in vapor state, as liquid fuel is not combustible.
Note: In order to eliminate any confusion, it is important to note that for
the fuel injection process fuel must be in a liquid state in order to be
properly metered by the fuel injector. Vapor formation before the
injection process is highly undesirable and can cause a host of
driveability problems (See Sec. 2.2.7.2 and 8.4.1). However, it is
important for the actual combustion process that fuel is in the vapor
state. This is typically achieved through the fuel spray and particle size
characteristics of the liquid fuel after it is injected. Other factors, such as
injection time, fuel spray targeting, residence time and the air induction
characteristics all play a role in this process.
Throughout this manual, it should be assumed that when A/F ratios are
stated as being stoichiometric, it is in reference to standard nonoxygenated fuels unless specifically stated otherwise. It should be noted
that oxygenates (MTBE, ethanol) have a higher (lower numerically)
stoichiometric air/fuel ratio than standard gasoline. This effectively
means that more fuel is needed for the same intake airflow to obtain
complete combustion.
2.2.1.1 Stoichiometric Mixtures, Definitions
As noted in the last section, stoichiometric A/F refers to the quantitatively
derived ratio of air to fuel that will allow the chemical process of
combustion to be delivered to ideal equilibrium. Typical values for this
are 14.7:1 for standard, non-oxygenated gasoline. Stoichiometry values
for alternate fuel blends are shown in Table 2-1.
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Since the A/F will vary depending on the makeup of hydrocarbons in the
gasoline, a more appropriate method for referencing A/F is to use a
normalized value. In this way, we can refer to stoichiometric A/F as equal
to 1, regardless of the makeup of the gasoline. Two such terms are
commonly used:
• Lambda (λ), where λ= (A/F actual) / (A/F stoichiometric). This is also
referred to as the excess air ratio.
• λ > 1.00 for lean mixtures
• λ < 1.00 for rich mixtures
• Equivalence Ratio (φ), where φ= (F/A actual) / (F/A stoichiometric)
• φ < 1.00 for lean mixtures
• φ > 1.00 for rich mixtures
Fuel Type Stoichiometric Air /Fuel
Typical Unleaded
Gasoline
10% Ethanol Blend 13.9
24% Ethanol Blend 13.3
85% Ethanol Blend* 9.95
15% MTBE Blend 14.1
100% Ethanol* 9.0
*Non-standard fuels requiring special fuel rail and injector
components.
Table 2-1 - Stoichiometry of Alternate Fuel Blends
2.2.1.2 Stoichiometric “Ideal” Combustion Mixtures
Ratio
14.5 (Range 14.2 – 14.8)
Complete or “ideal” combustion produces by-products of carbon dioxide
(CO2), nitrogen (N2) and water (H2O). However, ideal combustion does
not occur in an actual engine. The chemical equilibrium required is often
difficult to achieve. Transient operating conditions, combustion chamber
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design, fuel quality (contaminants and other non-combustibles) and the
limited time available to complete the process (especially at high engine
rpm.) all contribute to less than ideal combustion.
A catalytic converter is usually used in the exhaust system to transform
the harmful by-products of combustion to less harmful gases:
HC, CO, NOx Three-way catalyst H2O, CO2, N2
Figure 2-2 illustrates the relationship between the air/fuel ratio and
catalytic converter efficiency. Optimum converter efficiency is achieved
at 14.5 +/- 0.3 A/F.
2.2.1.3 Rich Mixtures
• A mixture with "excess fuel"; also described by a Lambda < 1.00 or an
equivalence ratio >1.00
Rich mixtures have a larger proportion of fuel relative to the
stoichiometric ratio, which typically results in increased fuel consumption
and hydrocarbon emissions. As the amount of fuel in the ratio increases, it
displaces intake air, and thus oxygen, in the mixture. This lack of oxygen
results in some portion of the fuel to be incompletely combusted, thus
increasing hydrocarbon emissions. If excessively rich, the lack of oxygen
can also result in a large increase in carbon monoxide emissions (CO).
Controlled rich mixtures are regularly used at vehicle start-up when the
engine is cold. This is done to help ensure vehicle start and performance
quality, as it is more difficult for fuel to vaporize under these conditions.
Rich mixtures may also be used under conditions where maximum engine
power is required, or to help protect the catalytic converter under high
load conditions.
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Converter Efficiency (%)
100
80
60
40
Conversion Efficiency for a Typical Three-Way Catalyst
Rich Region: where little O
available, so reduction can easily
be done to NO
means stripping away oxygen)
. (Reduction
X
2
is
Lean Region: where excess O2 is
available to oxidize HC & CO.
(Oxidizing means adding oxygen)
Window
CO
+/- 0.3
NO
13.0 14.0 14.6 15.0 16.0
Figure 2-2 - Air Fuel Ratio Effect on Catalytic Converter Efficiency
2.2.1.4 Lean Mixtures
Air/Fuel Ratio
• A mixture with "excess air"; also described by a Lambda >1.00 or an
equivalence ratio <1.00
Lean mixtures have excess oxygen and higher combustion temperatures
resulting in increased oxides of nitrogen (NO
) emissions. Nitric oxide
x
(NO) is the primary oxide created. It forms at a significant rate when
combustion chamber temperatures are above 1200 oF (650oC.) The rate
of NOx formation increases with excess oxygen concentration,
temperature and time at temperature. NOx is typically highest just lean of
stoichiometry. Lean mixtures above a 16 – 17 to 1 air/fuel ratio decrease
NOx production due to the lowering of combustion temperatures.
While NOx production is an undesirable product of running slightly lean,
there are several benefits that can be realized by running lean of
stoichiometry. A controlled lean combustion process can reduce the
output of hydrocarbon (HC) and carbon monoxide (CO) emissions, as well
as reducing fuel consumption. Diluting the intake charge with a non-
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combustible dilutant can reduce NOx. One of the most common of these
is exhaust gas, recirculated into the mixture via an EGR system. (Ref.
Delphi EGR Applications Manual for more information on this process).
2.2.1.5 Non-Combustible Mixtures
Air/fuel ratios outside the combustible mixture limits (too rich or too lean)
cause engine misfire, reduced power, a significant increase in emissions
(primarily HC from unburned fuel) and poor overall engine performance.
Combustible mixture limits are dependent on many factors, some of which
are combustion chamber design, ignition system energy, fuel composition,
amount of EGR, etc.
2.2.2 Fuel Atomization
Fuel atomization is the transformation of bulk fuel into spray. Fuel enters
the intake port as an atomized stream. The fuel droplets evaporate when
they mix with the air and also when they contact a hot surface. When the
intake valve opens, the air/fuel mixture passes into the cylinder where it
mixes with residual exhaust gases. Combustion is initiated near the end of
the compression stroke when the spark plug fires.
The optimum fuel spray characteristics for a particular application are
dependent upon the following:
• Intake manifold design
• Mixture motion control device
• Combustion chamber characteristics
• Spark plug configuration
• Injector spray targeting
• Injection timing
• The temperature of the target area
These criteria must be validated.
Combustion requires vaporized fuel. One of the functions of the fuel
injector is to atomize the fuel. Smaller fuel particles are both easier to mix
uniformly with air and require less heat to vaporize. Fuel particle size is
dependent on system fuel pressure, spray pattern, and injector spray
orifice design.
Note
imits to these characteristics must be totally understood. Combustion
efficiency and rate are dependent on specific application and fundamental
engine design.
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2.2.3 Fuel Spray Characteristics and Injection Timing
For maximum vaporization, fuel is typically targeted at the intake valve,
as it is typically the hottest surface in the combustion chamber induction
path. Fuel is typically injected before the intake valve opens and is
allowed some residence time to allow the fuel to vaporize. Fuel
vaporization also occurs as the air/fuel mixture passes the valve on its way
toward the combustion chamber. As the time between valve events
decreases (as engine rpm increases), the time for vaporization is also
reduced.
PZEV (partial zero emission vehicle) exhaust emission regulations have
placed additional emphasis on fuel delivery (atomization and timing.) The
majority of the tailpipe emissions measured during a Federal Emissions
Test Procedure (FTP) are generated during the time period between engine
start and catalytic converter warm-up (reference section 2.2.7.3.)
Alternate fuel delivery schemes may be employed during this time period
to minimize emissions. Consult with your Delphi Applications Engineer
for more information.
Note
See Section 5 for
calibrating optimum
injection timing
Note
Reference Worldwide Emissions Standards booklet available from Delphi
or emissions regulations and test profiles.
Spray not targeted at the intake valve can be stored as liquid on the intake
port walls. The conditions when this collected fuel enters the combustion
chamber may be difficult to predict, affecting engine emissions and
driveability.
Typically, open intake valve fuel injection timing is not recommended for
conventional fuel injection systems with Multec 3.5 injectors because the
fuel bypasses the heating effects of the intake valve. If injection takes
place as the intake valve first opens, the reversion pulse at the end of the
exhaust stroke can divert the spray, greatly affecting both the targeting of
the spray and the particle size. If injection occurs just as the intake valve
closes, the fuel spray may be affected by a back flow of air caused by the
pressure wave generated by the valve’s closure.
Direct injection schemes that utilize open valve injection require specific
hardware. Please consult a Delphi representative for more information on
Delphi direct injection (DI) fuel systems.
This manual covers only the basics of spray particle size, targeting and
injector timing. Consult a Delphi Applications Engineer for more
information.
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2.2.4 Benefits of Electronic Fuel Injection Over Other Types of Fuel Systems
Electronic fuel injection has enabled engines to meet tighter exhaust
emissions standards through improved fuel control. Engine calibration
software can be programmed to deliver the precise amount of fuel required
by the engine under all operating conditions. Typical A/F ratio
distribution requirements are +/- 1.0 cylinder to cylinder
In addition, evaporative emissions standards require closed fuel systems
using seal rings and minimal tip leakage. The Multec 3.5 injector is a dry
coil design. There are no internal seal rings, eliminating possible sources
of evaporative emissions.
Purging the evaporative canister during engine operation requires better
control of lower fuel rates, placing greater demands on the low pulse
width capability of the injector (see section 2.4.3).
2.2.5 Impact of Transient Conditions on Combustion
See Section 3.9.1
The term "transient conditions" is used to describe a change in engine load
and/or operating conditions. The primary focus is in response to drivercommanded vehicle acceleration or deceleration maneuvers, but other
changes in state, such as transmission gear changes, torque converter lock
condition (automatic transmissions) and air conditioning compressor
engagement can impact fueling requirements. The impact of transient
conditions on combustion and emissions are typically magnified during
cold engine operating conditions.
During these transient conditions, the amount of fuel required and the
amount of fuel delivered may be different as there is likely to be some
"lag" between the actual change in state and the response of the fuel
injection system to these changes. In addition, fuel that builds up on
manifold walls or in crevices during steady state engine conditions may be
suddenly forced into the engine due to rapid changes in engine pressure
and airflow. This can be detrimental to driveability and emissions. These
differences in fuel delivery can be accounted for by software corrections
such as wall wetting compensations, deceleration enleanment and
acceleration enrichment.
When the vehicle is in a coasting (overrun) condition with the throttle
closed, the fuel supply to the cylinder can be stopped by shutting off the
injectors. This aids in further reducing the power output of the engine and
conserves fuel. Transitions into and out of this mode often require very
small amounts of fuel delivered in rapid fashion to minimize the impact on
vehicle performance and stability.
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Caution
Extreme transient conditions can require low pulse-widths. Commanded
ulse-widths must not fall below the application’s minimum specifications.
Inconsistencies in injector flow, pulse-to-pulse and part-to-part result
when operated below minimum recommended ranges.
2.2.6 Impact of Fuel Composition
2.2.6.1 Overview
Gasoline is a complex variable mixture of hydrocarbons, and can include
oxygenates such as ethanol, MTBE, etc. The net overall effect on
combustion depends on both the average properties of the fuel, e.g.,
average hydrogen-to-carbon ratio (H/C) and the molar percent or
molecular weight of each of the hydrocarbon species present. The lower
molecular weight hydrocarbon constituents, which are easier to burn, tend
to increase fuel volatility, making it easier to vaporize the fuel. The
higher molecular weight constituents, which are harder to burn, tend to
reduce fuel volatility. The presence of these higher molecular weight
constituents may increase the potential for engine deposits. Reference
Figure 2-3 for fuel distillation curve vs temperature properties, and the
effects of changing distillation properties on vehicle and fuel system
performance.
Fuel composition is adjusted by the fuel supply companies throughout the
year to best match the volatility of the fuel to the climate in which the fuel
is used. Reference World Wide Fuel Charter or ASTM D4814, “Standard
Specification for Automotive Spark-Ignition Engine Fuel”. Fuels outside
these specifications can compromise fuel injector performance.
2.2.6.2 Gasoline Composition – Oxygenates – Reformulated Gasoline (RFG)
As part of the U.S. Clean Air Act of 1990, oxygenated fuels are required
in ozone non-attainment areas to help reduce CO emissions. Oxygenates
help reduce the reactivity of the exhaust gas, and thus help reduce smog
formation. The California Air Resource Board (CARB) has phased out
the use of MTBE as an oxygenate. CARB Phase III fuel was introduced
during 2003 and uses ethanol as the oxygenate. In addition, many states
in the US have or are planning to phase out MTBE.
MTBE and Ethanol are common oxygenates used to provide the additional
oxygen in the combustion process to reduce CO emissions. Oxygenates
have higher stoichiometric air fuel ratios (rich relative to standard
gasolines) for optimum combustion, due to a reduction in the energy
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content of the fuel (see Table 2-1.) This must be considered in the flow
sizing of the injector and fuel supply system, as a given application will
have slightly higher fuel consumption depending on the percentage of
oxygenate in the fuel.
Ref. Sec. 2.2.7.2 & 8.4.1
Note:
In addition, small additions of these oxygenated fuels can greatly increase
the volatility of the fuel. Since this may require the fuel system
calibration to be adjusted to accommodate these types of fuels, vehicle
development testing at both hot and cold temperature extremes with these
fuels is recommended.
In general, increasing oxygenate concentrations tend to increase
deterioration of plastics and swell in elastomers. Because oxygenates
increase the solubility of water in the fuel, use of these types of fuels can
accelerate wear and corrosion in fuel system components.
For high ethanol concentration fuels, deviations from regulated or typical
levels of pHe and corrosives could compromise fuel injector performance.
Delphi tests most fuel system components to be robust to typically
available U.S. oxygenated fuel blends (maximum 2.7 mass% oxygen,
which is roughly 15% MTBE or 10% denatured ethanol). Higher
ercentages of alcohols will shorten the operating life of the injector.
Please consult a Delphi representative to obtain a current list of all fuels
the Multec 3.5 Fuel Injector has been validated in.
Specific injector models are available from Delphi with enhancements to
operate with higher oxygenated blends.
2.2.6.3 Gasoline Composition
The following provides an overview of how other constituents in gasoline
can impact both performance and emissions.
2.2.6.3.1 Paraffins (approx. 54 %mass)
As paraffin concentration increases:
• Soot formation reduced
• Resistance to surface ignition increased
• Reduced heating value (thus lower energy content and increased fuel
consumption)
• Effects octane rating
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2.2.6.3.2 Aromatics (approx. 35 %mass)
As aromatic concentration increases:
• Increases octane rating
• Increases energy content (increases fuel economy)
• Makes fuel more difficult to burn
• Reduces fuel volatility
• Increases self ignition temperature
• Increases soot formation
• Increases deterioration of fuel system plastics and elastomer (swell)
• Increases solubility of water
• Reactivity of exhaust gas (smog formation)
2.2.6.3.3 Olefins (approx 10%)
2.2.6.3.4 Others
Olefins are unsaturated hydrocarbons that can lead to deposit formation on
intake valves and injector tips. Olefins are created in the refining process.
Gasolines with high levels of olefins require additional detergent chemical
additives to prevent deposit formation on the injector director plate.
Silicon and lead content in gasoline can be detrimental to oxygen sensors;
lead content can lead to products of combustion that can potentially cause
injector plugging and have been shown to be detrimental to both catalysts
and exhaust gas recirculation devices.
Sulfur in gasoline has been shown to reduce catalytic converter efficiency.
CARB regulations reduced sulfur to 30 ppm average 80 ppm max for Tier
2 emissions. The EPA will complete the phase in of these regulations in
2006.
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Figure 2-3 - Fuel Distillation Curve vs Temperature
2.2.6.4 Driveability Index
A more complete understanding of the impact of fuel volatility on fuel
system performance can be obtained by measuring the fuel’s distillation
curve and computing the driveability index (DI). Figure 2-3 shows a fuel
distillation curve and which aspects of engine performance are impacted
for a typical gasoline.
DI = 1.5T
evaporated temperatures measured by ASTM D86. Temperatures are
specified in °F.
AAMA and ASTM proposed limits for DI are 1200 to 1290 max. DI
values exceeding these limits have been documented to produce customer
dissatisfaction due to reduced driveability.
+ 3T50 +T90 where T10, T50, T90 are the 10%, 50% and 90 %
10
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2.2.7 Engine-Vehicle Environment
2.2.7.1 Impact of High Engine Temperatures on Combustion
As the engine and engine compartment temperatures increase, several
factors must be considered to obtain optimum combustion. Hot air
entering the induction system is lower in density and results in a reduced
mass air flow rate. To maintain the optimum air/fuel ratio, the engine
controller must reduce the amount of metered fuel. Speed density
systems, which do not have the ability to directly measure intake airflow,
utilize an inlet air temperature sensor to estimate the reduction in mass
airflow at elevated temperatures. Mass airflow systems are capable of
reading reduced airflow rates directly from the calibrated air flow meter
Refer to Section 5
ote: Low pulse-widths, such as at idle or during overrun conditions,
could fall below the injector minimum working flow range under elevated
temperature conditions. This could cause pulse-to-pulse variations that
directly affect idle quality. The impact on idle quality depends on the
injector firing scheme. Typically the minimum commanded pulse width is
limited in the engine control software.
It is important to consider these operating conditions when determining
the proper flow size for the injector.
2.2.7.2 High Ambient Temperature Startability
Reference section 8.4.1
or Hot Fuel Handling
Tests.
While high ambient temperature conditions must be evaluated for most
engine components, several conditions in combination can cause specific
problems for the fuel system.
In general, fuel system components reach their peak temperatures after the
vehicle has been shut down. This period is usually referred to as the soak
period. It is during this soak period that problems may occur if the vehicle
is re-started.
During normal operation, the fuel injector does not typically see extreme
temperatures because the fuel flowing through the tip helps dissipate heat
energy. When the vehicle is shut down, fuel is no longer flowing through
the injector. Injector tip temperatures rise and can eventually reach an
equilibrium temperature with their surrounding environment in the intake
manifold or cylinder head.
The problems typically encountered are due to the premature vaporization
of fuel, either upstream of the metering orifice in the injector or as liquid
fuel passes through the metering orifice and "flashes" to vapor. Although
the fuel system is under pressure, the temperature can rise to the point that
this pressure is no longer able to suppress formation of vapor.
The likelihood that a particular fuel will vaporize is characterized by its
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