Manufacturing Cost Estimation for 

Class 2B/3 CNG Systems 
EPA-420-D-15-004 

June 2015

NOTICE 

This technical report does not necessarily represent final EPA decisions or 

positions. It is intended to present technical analysis of issues using data 

that are currently available. The purpose in the release of such reports is to 

facilitate the exchange of technical information and to inform the public of 

technical developments.

Assessment and Standards Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency

Prepared for EPA by

FEV North America, Inc.

EPA Contract No. EP-C-12-014 WA2-03

Manufacturing Cost Estimation for 

Class 2B/3 CNG Systems
Analysis Report BAV-P310324-03

June 26, 2015 

Page 3 

Table of Contents 

Executive Summary 7

1. Introduction and Program Objectives 8

1.1. Objective 8

1.2. Vehicle Selection 8

1.3. Background 8

2. System Overview & Cost Structure 11

2.1. System Design 11

2.2. Hardware 13

2.3. BOM Creation 15

2.4. Costing Methodology 17

3. Storage Subsystem 18

3.1. Tank Cover Sub-Subsystem 18

3.2. Cradle Sub-Subsystem 21

3.3. Tank Sub-Subsystem 23

4. Safety Devices Subsystem 30

4.1. High Pressure Lock-Off Valve Sub-Subsystem 30

4.2. Safety Relief Valve Sub-Subsystem 33

4.3. Excess Flow Valve Sub-Subsystem 35

4.4. Purge Sub-Subsystem 38

5. High Pressure Circuit Subsystem 39

5.1. Filler (Refueling) Sub-Subsystem 39

5.2. Distribution, High Pressure Sub-Subsystem 41

5.3. Filter Sub-Subsystem 42

5.4. Pressure Regulator Sub-Subsystem 44

6. Low Pressure Circuit Subsystem 45

6.1. Distribution, Low Pressure Sub-Subsystem 45

6.2. Fuel Rails Sub-Subsystem 47

6.3. Fuel Injector Sub-Subsystem 48

7. Controls Subsystem 50

7.1. Control Module Sub-Subsystem 50

7.2. Wire Harnesses Sub-Subsystem 53

8. Cost Summary and Conclusion 54

9. Appendix A 57
Analysis Report BAV-P310324-03

June 26, 2015 

Page 4 

List of Figures 

Figure 1- Chevrolet Silverado 2500 CNG 8

Figure 2- Compressed Natural Gas (CNG) System 12

Figure 3- CNG System Hardware 14

Figure 4- Storage Subsystem 18

Figure 5- Tank Cover Sub-Subsystem – Assembled 19

Figure 6- Tank Cover Sub-Subsystem – Components 20

Figure 7- Cradle Sub-Subsystem – Components 21

Figure 8- CNG Tank 23

Figure 9- CNG Tank Label 24

Figure 10- Silverado CNG Tank Section # 1 24

Figure 11- Silverado CNG Tank Section # 2 25

Figure 12- Step 1: Seamless Aluminum Tube Cut to Length 26

Figure 13- Step 3: Preheating of Blank Prior to Spin Form 26

Figure 14- Step 4: Blank Chucked in Spin Form Machine 27

Figure 15- Step 4-1: Spin Forming 27

Figure 16- Step 4-2: Spin Forming 28

Figure 17- Step 5: Heat Treatment (Stress Relief) 28

Figure 18- Step 8: Carbon Fiber Wrapping 29

Figure 19- Step 8: Carbon Fiber Wrapping (Continued) 29

Figure 20- High Pressure Lock-Off Sub-Subsystem – Assembled 31

Figure 21- High Pressure Lock-Off Sub-Subsystem – Components 31

Figure 22- High Pressure Lock-Off – Exploded View 32

Figure 23- Safety Relief Valve – Assembled 33

Figure 24- Safety Relief Valve – Components 34

Figure 25- Safety Relief Valve – Exploded View 34

Figure 26- Excess Flow Valve – Assembled 36

Figure 27- Excess Flow Valve – Exploded 36

Figure 28- Purge Sub-Subsystem – Components. 38

Figure 29- Filler Sub-Subsystem – Components 39

Figure 30- Fill Port – Exploded View 39

Figure 31- Distribution, High Pressure Sub-Subsystem 41

Figure 32- Filter Sub-Subsystem – Components 42

Figure 33- CNG Filter – Exploded View 42

Figure 34- Pressure Regulator Sub-Subsystem – Components 44

Figure 35- Pressure Regulator – Exploded View 44
Analysis Report BAV-P310324-03

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Page 5 

Figure 36- Distribution, Low Pressure Sub-Subsystem – Components 46

Figure 37- Fuel Rails Sub-Subsystem – Components 47

Figure 38- Injector Nozzle – Components 47

Figure 39- Fuel Injector Sub-Subsystem – Components 48

Figure 40- CNG Fuel Injector – Sectioned 49

Figure 41- Control Module Sub-Subsystem – Components 50

Figure 42- CNG ECU – Exploded View 50

Figure 43- CNG ECU Board with Circuit ID numbers – Top 51

Figure 44- CNG ECU Board with Circuit ID numbers – Bottom 52

Figure 45- Wire Harness Sub-Subsystem 53

Figure 46- CNG Subsystems 55

Figure 47- Manufacturing and Mark-up Cost 55
Analysis Report BAV-P310324-03

June 26, 2015 

Page 6 

List of Tables 

Table 1- U.S. Product Supplied of Finished Motor Gasoline 9

Table 2- U.S. Alternative Fueling Stations by Fuel Type 10

Table 3- BOM Compressed Natural Gas (CNG) System 16

Table 4- BOM Tank Cover Sub-Subsystem 20

Table 5- BOM Cradle Sub-Subsystem 22

Table 6- BOM CNG Tank Sub-Subsystem 30

Table 7- BOM High Pressure Lock-Off Valve Sub-Subsystem 32

Table 8- BOM Safety Relief Valve Sub-Subsystem 35

Table 9- BOM Excess Flow Valve Sub-Subsystem 37

Table 10- BOM Purge Sub-Subsystem 38

Table 11- BOM Filler (Refueling) Sub-Subsystem 40

Table 12- BOM Distribution, High Pressure Sub-Subsystem 41

Table 13- BOM Filter Sub-Subsystem 43

Table 14- BOM Pressure Regulator Sub-Subsystem 45

Table 15- BOM Distribution, Low Pressure Sub-Subsystem 46

Table 16- BOM Fuel Rails Sub-Subsystem 48

Table 17- BOM Fuel Injectors Sub-Subsystem 49

Table 18- BOM Control Module Sub-Subsystem 52

Table 19- BOM Wire Harnesses Sub-Subsystem 53

Table 20 - CNG Subsystem Cost Summary Overview 54

Table 21 - Complete Cost Summary (CMAT) – CNG System 57
Analysis Report BAV-P310324-03

June 26, 2015 

Page 7 

Executive Summary

The United States Environmental Protection Agency (EPA) contracted with FEV North 

America, Inc., to determine incremental direct manufacturing costs for a complete CNG 

fuel system. The system selected to represent the light-duty vehicle segment was a 

2013 Chevrolet Silverado equipped with General Motors Bi-Fuel option. The Silverado 

was purchased by FEV and all CNG related components were identified. The vehicle 

was then completely disassembled. Names, photos and weights were assigned to all 

CNG related components and compiled in a Bill of Materials (BOM). All CNG system 

components were reviewed in detail and cost estimated using FEV’s standard costing 

process. All costs were developed using a volume assumption of 450,000 units per 

year. This cost analysis is inclusive of all associated assembly cost from component to 

vehicle. Calculations were performed to determine equipment sizing, cycle times and 

material usage requirements. FEV utilized its extensive database of rates for 

equipment, labor, material, end item scrap, selling, general and administrative (SG&A),

profit, and engineering, design and testing (ED&T) to develop costs representative of 

what an OEM would incur for such a system in high volume automotive manufacturing.

Cost for the five (5) subsystems are as follows: 

1. Storage-$1,360 

2. Safety Devices-$151

3. High Pressure Circuit-$184 

4. Low Pressure Circuit-$278

5. Controls-$303 

Total System cost = $2,276

Sixty (60) percent of the system cost can be attributed to CNG storage. Gasoline’s 17x 

energy density factor over natural gas at atmospheric conditions creates a storage 

challenge for CNG. High pressure storage (3600psi) is required to minimize this energy 

density differential. Pressure, weight, and safety requirements all contribute to CNG 

tank costs. The one-piece, seamless, carbon fiber reinforced tank undergoes a twelve 

(12) step manufacturing process before completion. In light of carbon fiber processing 

improvements like pre-preg fibers, the process of wrapping is a time consuming cost 

driver. Make up 44% of the tank cost. The wrapping process and material cost of 

carbon fiber. 

The System is comprised of: high pressure lock-off, pressure relief device, and excess 

flow valve. 

High Pressure Circuit includes; refueling filler, fuel lines, filter and pressure regulator. 

Low Pressure Circuit includes; fuel lines, fuel rails and CNG injectors. 

Controls include; ECU, intake air temperature module, fuel pump module, and wiring. 

General Motors Bi-Fuel System was designed as an add-on to an existing gasoline 

engine. As an add-on, the CNG system has its own ECU requiring Intake Air 

Temperature and Fuel Pump control modules. A dedicated CNG system would 

eliminate these components, reducing overall vehicle cost. 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 8 

1. Introduction and Program Objectives

1.1. Objective 

The objective of this study is to develop cost for a complete light-duty truck CNG 

system, manufactured at high production volume (450,000 units per year). 

1.2. Vehicle Selection 

A 2013 Silverado 2500 4WD LT Extended CAB truck with bi-fuel option was selected as 

a representative light-duty passenger vehicle CNG system. The truck was equipped 

with a 6.0L Vortec engine, GM designation LC8. The CNG system is modular and was 

designed as an add-on option to GM’s existing product. 

Figure 1- Chevrolet Silverado 2500 CNG 

(Source: FEV, Inc. photos) 

1.3. Background 

For the same energy output, combustion of CNG produces 29% less carbon dioxide 

than combustion of oil base fuels (i.e., gasoline). ‘In most applications, using natural 

gas produces less of the following substances than oil or coal: carbon dioxide (CO2), 

the primary greenhouse gas; sulfur dioxide, which is the primary precursor of acid rain; 

nitrogen oxides, which is the primary precursor of smog; and particulate matter, which 

can affect health and visibility.’
Analysis Report BAV-P310324-03

June 26, 2015 

Page 9 

http://www.aga.org/ourissues/issuesummaries/Pages/EnvironmentalBenefitsofNaturalGas.aspx

In 2013 the US consumed 3.2 billion barrels of gasoline as shown in Table 1. In 

addition to fuel reduction technologies like turbo-downsizing and lightweighting, CNG 

offers another option to reducing petroleum-based fuel consumption. 

Table 1- U.S. Product Supplied of Finished Motor Gasoline 

http://www.eia.gov/tools/faqs/faq.cfm?id=23&t=10

‘CNG conversions can provide stability against fluctuating fuel prices as well as lower 

vehicle operating costs for fleet administrators. CNG sells for an average of $2.10 per 

Gasoline Gallon Equivalent (GGE), and is as low as $1 in some parts of the country, 

representing a significant savings over unleaded regular fuel. The national price range 

for unleaded regular fuel is $2.25 - $3.50 per gallon’. 

http://corporate.ford.com/news-center/press-releases-detail/first-cng-capable-2014-fordf-150-rolls-off-the-line-in-kansas

Storing enough natural gas in a motor vehicle to provide a sufficient range is a 

challenge with CNG. To improve upon its lower energy density, natural gas is stored at 

3600 psi. Even at this pressure fuel tank size is significantly larger. For example the 

Silverado CNG tank is rated at 17 GGE gallons however, the actual internal tank 

volume as measured after sectioning by FEV is approximately 55 gallons. GGE is 

based on an equal measure of energy making it possible to compare cost per unit of 

alternate fuels, GGE in terms of CNG Gas (Volume/Pressure/Temp) = 1 Gallon of Gas 

(Temp, Pressure=atm). For example 1 GGE of CNG and 1 gallon of gasoline are 

equivalent. 

At this time, the primary drawbacks of CNG are the underdeveloped vehicle refueling 

infrastructure and the fuel storage requirements. As of 2013 there were approximately 

1,260 CNG refueling stations in the country. 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 10

Table 2- U.S. Alternative Fueling Stations by Fuel Type 

http://www.afdc.energy.gov/data/10332

Implementing a high pressure CNG system in a passenger vehicle requires safety 

provisions not needed with conventional gasoline. Directly mounted to the CNG tank 

are two (2) safety devices. The first is an electronic flow lock preventing CNG from 

leaving the tank unless permitted by the ECU. The second is a pressure relief valve 

with back-up burst disc to prevent overpressure in the CNG system. A manual isolation 

valve is located after the tank for service and an additional electronic flow lock is located 

in the pressure regulator. A flow fuse is used to cut-off flow in the event the system is 

ruptured and the intended gas flow rate is exceeded. 

Higher combustion temperatures and corrosive properties of natural gas require 

hardened exhaust valves and intake/exhaust valve seats. 

http://www.gmfleet.com/vehicle-overviews/fuel-efficiency/bi-fuel.html
Analysis Report BAV-P310324-03

June 26, 2015 

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2. System Overview & Cost Structure

2.1. System Design 

Figure 2 is a schematic representation of the CNG system generated as an aid to 

understand the components and their function. The system was broken into five (5) 

subsystems and color coded at the bottom of the figure. The CNG tank manages fuel 

pressures up to 3600 psi when full. Directly mounted to the CNG tank are the Safety 

Relief Valve and High Pressure Lock-off (HPL) solenoid. 

Connecting to the underbody purge line is the safety relief assembly. A spring piston 

with plastic face seal opens when the tank pressure exceeds the design limit. Over 

temperature conditions exceeding the melting point of the plastic face seal will also 

open this valve. The pressure burst disc is a secondary safety device protecting the 

tank from over pressure. 

The opposite end of the tank mounts the HPL solenoid. This valve requires activation 

before any gas is permitted to exit the tank. Integrated into this assembly is a manual 

purge valve, providing a means to vent the system to the atmosphere, and a 

temperature transmitter extending into the tank cavity. 

Following the HPL solenoid is the excess flow valve. This device protects the system 

from a downstream rupture. If the gas flow exceeds the limit of this valve it closes. 

When pressure across the valve equalizes the valve automatically resets. 

The fill circuit consists of a quick release with integrated check valve for ensuring oneway flow. The quick release serves as the connection point for refueling. A secondary 

check valve located after the quick release again ensures one-way flow. The fill circuit 

continues to the tank with reverse flow through both the excess flow valve and HPL 

solenoid. 

Continuing from the excess flow valve, fuel travels through a manual ball (service) valve 

to the filter before entering the pressure regulator. Integrated into the pressure 

regulator is a normally closed solenoid valve in addition to pressure and temperature 

transmitters. The solenoid valve provides another level of security from unintended fuel 

flow. Heat absorption caused by the expansion of gas requires a heating circuit which 

ties into the engine cooling system. The pressure regulator reduces pressure to 100 

psig. 

Following the pressure regulator, fuel is routed to the fuel rails supplying eight (8) 

individual CNG injectors. The injectors terminate via hose to port mounted nozzles in 

the intake manifold. 
Analysis Report BAV-P310324-03

June 26, 2015 

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Figure 2- Compressed Natural Gas (CNG) System 

(Source: FEV, Inc. photos) 
Analysis Report BAV-P310324-03

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2.2. Hardware 

Primary CNG hardware is shown in Figure 3 in order as follows:

 Type 3 CNG Tank 

 Manufacturer: Structural Composites Industries; P/N:319875 

 Construction: Seamless Aluminum, Carbon Fiber reinforced 

 High Pressure Lock-Off (HPL) 

 Manufacturer: GFI Control Systems; P/N:PT13F0172 

 Construction: Billet Aluminum 

 Features: Temperature Measurement, Manual Purge Valve 

 Pressure Relief Device (PRD) 

 Manufacturer: GFI Control Systems; P/N:PRD-120BD 

 Construction: Billet Aluminum 

 Flow Fuse 

 Manufacturer: HOKE; P/N:HVX316 

 Construction: 316 stainless steel, brass, Monel®, Hastelloy® C-276

 Distribution Lines 

 Seamless Stainless Steel & Stainless Steel Jacketed PTFE 

 Filter 

 Manufacturer: Parker; P/N:FFC-112 SAE-10

 Construction: Billet Aluminum, Coalescing Media Filter 

 High Pressure Regulator (HPR) 

 Manufacturer: GFI Control Systems; P/N:P214-980

 Construction: Forged Aluminum 

 Features: High Pressure Shut-Off Solenoid, High Pressure Transducer, MAP 

referencing 

 Fuel Rail 

 Billet Aluminum 

 Fuel Injector 

 Manufacturer: AC Delco; P/N:22991067 

 Engine Control Unit (ECU) 

 Manufacturer: Fly SF; P/N:028705/9-V 

 Control Modules – Intake Air Temperature (IAT), Fuel Pump 

 Manufacturer: IMPCO Automotive; P/N: MD-53497-001, MD-54548-001

 Wiring 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 14

Figure 3- CNG System Hardware

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 15

2.3. BOM Creation 

The CNG system was disassembled starting with the tank, following the flow path, and 

ending with the fuel injectors. Assemblies were removed from the vehicle in groups that 

were thought to represent actual assembly. After removal from the vehicle 

assembles/components were photographed, weighed and tagged. 

The first step in disassembly of the CNG system was to purge all CNG from the tank. 

This was done by releasing the manual purge valve and deactivating the solenoid lockoff valve. Next, the tank, cradle and related hardware were removed from the bed of 

the truck. Subsequently in conjunction with another study the entire truck was 

disassembled and all CNG related system components were removed, named, 

photographed, weighted and logged into a Bill of Material (BOM). 

The CNG system was categorized into five (5) main Sub-Systems: Storage, Safety 

Devices, High Pressure Circuit, Low Pressure Circuit, and Controls. The storage 

subsystem includes the tank cover, tank cradle, and tank. The Safety Devices 

subsystem includes the high pressure lock-off, high pressure relief device, and excess 

flow valve. The high pressure circuit includes all high pressure fuel lines as well as fuel 

filter and pressure regulator. The low pressure circuit includes all low pressure fuel 

lines as well as cooling lines associated with the pressure regulator heating circuit. Also 

included in this subsystem are the fuel rail and fuel injectors. The wiring harness, 

control modules and ECU are included in the Controls Subsystem. 

The BOM structure shown in Table 3 details the subsystems and Sub-Subsystems 

which can be identified in the system schematic as segregated color shaded areas. 

The ‘Purge’ and ‘Distribution, Low Pressure’ Sub-Subsystems are shaded darker to 

highlight included plumbing. 

Every Sub-Subsystem, assembly, or component listed in the BOM features: mass, 

photo link, cost, and quote link. 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 16

Table 3- BOM Compressed Natural Gas (CNG) System 

QTY

Mass

0 - Top Level

123456789

10

Total Mass 

(Unit Mass x qty.)

"kg"

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889

20 01 01 Tank Cover Sub-Subsystem 1 33.650

20 01 02 Cradle Sub-Subsystem 1 78.280

20 01 03 Tank Sub-Subsystem 1 97.959

20 02 00 Safety Devices Subsystem 1 6.603

20 02 01 High Pressure Lock-Off Valve (HPLV) Sub-Subsystem 1 3.676

20 02 02 Safety Relief Valve Sub-Subsystem 1 1.004

20 02 03 Excess Flow Valve Sub-Subsystem 1 0.463

20 02 04 Purge Sub-Subsystem 1 1.460

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 03 01 Filler (Refueling) Sub-Subsystem 1 0.637

20 03 02 Distribution, High Pressure Sub-Subsystem 1 2.387

20 03 03 Filter Sub-Subsystem 1 0.613

20 03 04 Pressure Regulator Sub-Subsystem 1 4.095

20 04 00 Low Pressure Circuit Subsystem 1 8.622

20 04 01 Distribution, Low Pressure Sub-Subsystem 1 4.621

20 04 02 Fuel Rails Sub-Subsystem 1 3.825

20 04 03 Fuel Injectors Sub-Subsystem 8 0.176

20 05 00 Controls Subsystem 1 6.488

20 05 01 Control Module Sub-Subsystem 1 3.688

20 05 02 Wire Harnesses Sub-Subsystem 1 2.800

Part Numbering Part Name/Description System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Attribute 

Data

Product Structure

Quantity
Analysis Report BAV-P310324-03

June 26, 2015 

Page 17

2.4. Costing Methodology 

This cost analysis is a full system complete evaluation inclusive off all hardware 

associated with the CNG system. Included in the cost is component assembly to the 

vehicle. The CNG system as analyzed is a low-volume design, often utilizing off-theshelf hardware. On specific components, where a high volume manufacturing choice 

was clear, alternative manufacturing assumptions were made. For example, the safety 

relief protection collar was manufactured from billet however it was quoted as a die 

casting. Such assumptions are noted in detail throughout the body of this report. The 

volume assumption for cost estimation was 450,000 vehicles per year. 

Costs were developed for all critical components by detailing each operation in a 

Manufacturing Assumptions Quote Sheet (MAQS). Process calculators were used to 

determine equipment size and corresponding rate ($/hr), cycle time (seconds) and 

material usage (kg). For example, the Pressure Regulator Cap was identified as an 

aluminum die casting. The number of slide pulls, cavities, part width, part height, 

average wall thickness, parting line area, cavity surface area, and max wall thickness 

were all used to determine the die-casting machine size, cycle time and material usage. 

This information was then transferred to the MAQS where rates are pulled in for 

material, labor, manufacturing overhead/burden, end item scrap, SG&A, profit, and 

ED&T. Cost contributions are then calculated for these core cost elements. Similar 

process calculators are used for subsequent processing such as machining, where all 

machine features are measured, speed and feed rates assigned based on the 

respective material, and feed times calculated. In addition pallet changes, tool changes, 

rapid times, as well as estimated work pieces per fixture are used to estimate the total 

cycle time. Finally all processes are summed, end item packaging estimated, and total 

cost calculated. Cost contributions for the core cost elements are then linked to the 

Cost Model Analysis Template (CMAT). The CMAT incorporates cost data from various 

Sub-Subsystems into one summary sheet. Process costs were estimated as follows: 

1. Detailed assessment of manufacturing processes used to create the component 

2. Populate appropriate process calculator, identifying equipment size, cycle time, 

and material usage 

3. Transfer data from step 2 into quotation sheet and assign labor resources 

4. Repeat for all manufacturing processes required 

5. Repeat for all components in Sub-Subsystem 

6. Evaluate Sub-Subsystem assembly requirements including: number of stations, 

level of automation, burden rate, number of operators, and cycle time 

7. Evaluate vehicle assembly requirements including: number of stations, level of 

automation, burden rate, number of operators, and cycle time 

8. Assess packaging needs and estimate packaging costs 
Analysis Report BAV-P310324-03

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3. Storage Subsystem

The storage subsystem includes all hardware associated with the CNG tank. It is 

subdivided into the following Sub-Subsystems: 

 Tank Cover Sub-Subsystem 

 Cradle Sub-Subsystem 

 Tank Sub-Subsystem 

Figure 4- Storage Subsystem 

(Source: FEV, Inc. photos)

3.1. Tank Cover Sub-Subsystem 

Figure 5 shows the tank cover as assembled in the bed of the Silverado. The cover 

fastens to the cradle and cover mount bracket. 
Analysis Report BAV-P310324-03

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Figure 5- Tank Cover Sub-Subsystem – Assembled 

(Source: FEV, Inc. photos)

The Tank Cover Sub-Subsystem includes the fabricated diamond plate aluminum tank 

cover with access door, steel bracket, and associated fasteners as shown in Figure 6. 

For high volume production the Tank Cover was estimated as multiple stampings 

assembled as a weldment. The cover mount was heavy gauge material and also 

processed as a multiple stamping weldment. 
Analysis Report BAV-P310324-03

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Figure 6- Tank Cover Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

The bill of materials for Tank Cover Sub-Subsystem is shown in Table 4. SubSubsystem mass is 33.7 kg and the cost is $94. 

Table 4- BOM Tank Cover Sub-Subsystem

QTY Attribute 

Data

0 - Top Level

12345678910 Total Mass (Unit Mass x qty.) "kg"

20 00 00 Compressed Natural Gas System 239.334 $2,209

20 01 00 Storage Subsystem 1 209.925 $1,361

20 01 01 Tank Cover Sub-Subsystem 1 33.650 $94

20 01 01 Tank Cover 1 21.508

20 01 01 Bolt, Tank Cover 9 0.189

20 01 01 Cover Mount, Cradle, Tank 1 11.425

20 01 01 Bolt, Long, Cover Mount, Cradle, Tank 4 0.198

20 01 01 Bolt, Short, Cover Mount, Cradle, Tank 4 0.157

20 01 01 Nut, Cover Mount, Cradle, Tank 8 0.173

Part Numbering Part Name/Description Cost 

Analysis

System

Subsystem

Sub-Subsystem

System

Subsystem

Unit Cost

Sub-Subsystem

Product Structure

Quantity

Mass
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3.2. Cradle Sub-Subsystem 

The Cradle bolts into the box of the truck and serves as a mounting structure for the 

tank. The tank is secured to the cradle with two (2) rubber lined straps fastened with 

bolts. Cradle Sub-Subsystem components are shown in Figure 7.

Figure 7- Cradle Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

The Cradle Sub-Subsystem is a weldment of thirteen (13) individual stampings. Three 

(3) sprung retaining mechanisms were used to attach the cradle to the back of the truck 

box. These retainers were estimated by assuming a clipnut for high volume production. 
Analysis Report BAV-P310324-03

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The bill of materials for the Cradle Sub-Subsystem is shown in Table 5. SubSubsystem mass is 78.3 kg and the cost is $193. 

Table 5- BOM Cradle Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

12345678910 Total Mass (Unit Mass x qty.) "kg"

Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 01 01 Tank Cover Sub-Subsystem 1 33.650 20 01 01

20 01 02 Cradle Sub-Subsystem 1 78.280 20 01 02 $193

20 01 02 Bolt, Cradle, CNG Tank, Bottom 4 0.421 CIMG0020

20 01 02 Washer, Cradle, CNG Tank, Bottom 4 0.085 CIMG0021

20 01 02 Retainer Assembly, Cradle, CNG Tank, Back 3 0.517 CIMG0029

20 01 02 Collar, Cradle, CNG Tank, Back 3 0.090 CIMG0030

20 01 02 Bolt, Cradle, CNG Tank, Back 3 0.096 CIMG0032

20 01 02 Washer, Cradle, CNG Tank, Back 1 0.012 CIMG0033

20 01 02 Nut, Cradle, CNG Tank, Bottom 4 0.087 CIMG0035

20 01 02 Bolt, Strap, CNG Tank 4 0.325 CIMG0101

20 01 02 Washer, Strap, CNG Tank 18 0.167 CIMG0102

20 01 02 Straps, CNG Tank 2 4.221 CIMG0103

20 01 02 Bolt, Welded Strap, CNG Tank 2 0.150 CIMG0110

20 01 02 Cradle, CNG Tank 1 72.109 CIMG0112 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
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3.3. Tank Sub-Subsystem 

The CNG tank used on Silverado is a type 3 container made by Structural Composite 

Industries, a Worthington Cylinders Company as shown in Figure 8. CNG cylinders are 

available in 4 types, with type 1 being the heaviest and least expensive to type 4 being 

the lightest and most expensive. Type 3 tanks have a seamless and gas tight metal 

liner reinforced by composite wrap around the entire tank. The tank has a 15 year 

service life after which the tank must be replaced. Type 3 CNG tanks are pressure 

rated for 3600psi and are tested at 5500psi. Worthington manufactures all their 

cylinders to aviation standards, with a burst safety factor of at least 3.0 and with design 

verification impact testing about the full cylinder periphery. 

Figure 8- CNG Tank 

(Source: FEV, Inc. photos)

98kg / 216lbs
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Figure 9- CNG Tank Label 

(Source: FEV, Inc. photos)

Figure 9 show the label Figure 10 show the Silverado CNG Tank sectioned lengthwise. 

Composite wrap thickness thins around the radius and thickens around the ends of the 

tank. 

Figure 10- Silverado CNG Tank Section # 1 

(Source: FEV, Inc. photos)
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Figure 11- Silverado CNG Tank Section # 2 

(Source: FEV, Inc. photos)

Steps and images for CNG tank manufacturing are outlined below: 

Step 1: Saw seamless aluminum tube 

Step 2: Ultrasonic scanning of tube for imperfections 

Step 3: Preheat tube to initiate forming 

Step 4: Spin forming 

Step 5: Stress relief 

Step 6: Machine neck threads 

Step 7: Apply corrosion protectant 

Step 8: Composite carbon fiber wrap 

Step 9: Resin coating 

Step 10: Oven cure resin 

Step 11: Hydrostatic leak test 

Step 12: Random sample burst test 

http://www.youtube.com/watch?v=XxRiyCGtKgo
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Figure 12- Step 1: Seamless Aluminum Tube Cut to Length 

http://www.youtube.com/watch?v=-NDvGYfwTxs

Figure 13- Step 3: Preheating of Blank Prior to Spin Form 

http://www.youtube.com/watch?v=XxRiyCGtKgo
Analysis Report BAV-P310324-03

June 26, 2015 

Page 27

Figure 14- Step 4: Blank Chucked in Spin Form Machine 

http://www.youtube.com/watch?v=-NDvGYfwTxs

Figure 15- Step 4-1: Spin Forming

http://www.youtube.com/watch?v=-NDvGYfwTxs
Analysis Report BAV-P310324-03

June 26, 2015 

Page 28

Figure 16- Step 4-2: Spin Forming

http://www.youtube.com/watch?v=-NDvGYfwTxs

Figure 17- Step 5: Heat Treatment (Stress Relief) 

http://www.youtube.com/watch?v=XxRiyCGtKgo
Analysis Report BAV-P310324-03

June 26, 2015 

Page 29

Figure 18- Step 8: Carbon Fiber Wrapping 

http://www.youtube.com/watch?v=XxRiyCGtKgo

Figure 19- Step 8: Carbon Fiber Wrapping (Continued) 

http://www.fleetsandfuels.com/fuels/cng/2012/11/cleanng-readies-all-new-cngtank/attachment/cleanng_magmacel-1111
Analysis Report BAV-P310324-03

June 26, 2015 

Page 30

The bill of materials for the CNG Tank is shown in Table 6. Tank mass is 98 kg and the 

cost is $1,073. 

Table 6- BOM CNG Tank Sub-Subsystem 

4. Safety Devices Subsystem

4.1. High Pressure Lock-Off Valve Sub-Subsystem 

Figure 20 shows the High Pressure Lock-Off Valve directly connected to the driver’s 

side tank end. All components included in this Sub-Subsystem are shown in Figure 21. 

The protective cover and collar were assumed die casting and sand cast respectively 

for high volume production. The High Pressure Lock-off Valve body was machined from 

billet aluminum. All components making up the HPLV were identified in the cost file with 

the BOM part number and the ID number assigned in Figure 22. 

QTY Cost

Mass Photo

0 - Top Level

12345678910 Total Mass (Unit Mass x qty.) "kg"

Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 01 01 Tank Cover Sub-Subsystem 1 33.650 20 01 01

20 01 02 Cradle Sub-Subsystem 1 78.280 20 01 02

20 01 03 Tank Sub-Subsystem 1 97.959 20 01 03 $1,073

20 01 03 CNG Tank 1 97.959 CIMG0098 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 31

Figure 20- High Pressure Lock-Off Sub-Subsystem – Assembled 

(Source: FEV, Inc. photos)

Figure 21- High Pressure Lock-Off Sub-Subsystem – Components 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 32

Figure 22- High Pressure Lock-Off – Exploded View 

(Source: FEV, Inc. photos)

The bill of materials for the High Pressure Lock-Off Valve Sub-Subsystem is shown in 

Table 7. Mass is 3.7 kg and the cost is $55. 

Table 7- BOM High Pressure Lock-Off Valve Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603 #REF!

20 02 01 High Pressure Lock-Off Valve (HPLV) Sub-Subsystem 1 3.676 20 02 01 $55

20 02 01 Cover HLPV 1 0.469 CIMG0001

20 02 01 Bolt, Cover HLPV 4 0.007 CIMG0002

20 02 01 Collar, Protection, HPLV 2 2.256 CIMG0034

20 02 01 Bolt, Collar, Protection, HLPV 2 0.036 CIMG0036

20 02 01 P-Port Plug 1 0.015 CIMG0054

20 02 01 I/02 Port 1 0.025 CIMG0055

20 02 01 Line adapter, HLPV 1 0.046 CIMG0059

20 02 01 HLPV 1 0.822 CIMG0062 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 33

4.2. Safety Relief Valve Sub-Subsystem 

Figure 23 shows the Safety Relief Valve assembled to the passenger side tank end. 

Separate outlets are used for both the pressure/temperature relief valve and the burst 

disc. Both outlets join the manual purge valve outlet before continuing to the underbody 

atmospheric vent. 

Figure 23- Safety Relief Valve – Assembled 

(Source: FEV, Inc. photos)

Figure 24 identifies all components included in the Safety Relief Valve Sub-Subsystem. 

Unlike the protective collars of the HPLV, cross sectional thickness of the safety relief 

valve protective collars were able to be die cast. The protective cover was estimated as 

die cast as well. With exception to seals, washers, and fasteners, core components are 

all made from stainless steel and aluminum. 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 34

Figure 24- Safety Relief Valve – Components 

(Source: FEV, Inc. photos)

Figure 25 shows the components with the pressure relief device. In the left of the 

picture is the over pressure relief valve assembly with belleville spring set and heat 

sensitive seat. The second component in from the right is the rupture disc. 

Figure 25- Safety Relief Valve – Exploded View 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 35

The bill of materials for the Safety Relief Valve Sub-Subsystem is shown in Table 8. 

Mass is 1.0 kg and the cost is $26. 

Table 8- BOM Safety Relief Valve Sub-Subsystem 

4.3. Excess Flow Valve Sub-Subsystem 

Figure 26 shows the Excess Flow Valve Assembled to the High Pressure Lock-Off 

Valve. 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603 #REF!

20 02 01 High Pressure Lock-Off Valve (HPLV) Sub-Subsystem 1 3.676 20 02 01

20 02 02 Safety Relief Valve Sub-Subsystem 1 1.004 20 02 02 $26

20 02 02 Cover Plate, Relief Valve 1 0.121 CIMG0039

20 02 02 Bolt, Cover Plate, Relief Valve 4 0.030 CIMG0040

20 02 02 Collar, Notched, Temperature/Pressure Relief 1 0.155 CIMG0044

20 02 02 Collar, Temperature/Pressure Relief 1 0.187 CIMG0045

20 02 02 Bolt, Collar, Temperature/Pressure Relief 2 0.020 CIMG0045-1

20 02 02 Relief Valve Assembly, Pressure & Temperature 1 0.491 CIMG0063 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 36

Figure 26- Excess Flow Valve – Assembled 

(Source: FEV, Inc. photos)

Figure 27 shows the internal components comprising the Excess Flow Valve. All 

working components of this assembly are stainless steel. The spool diameters and 

faces are finished with grinding. The sealing surface of the mating housing are finished 

ground as well. The T-fitting is forged stainless steel. 

Figure 27- Excess Flow Valve – Exploded 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 37

The bill of materials for the Excess Flow Valve Sub-Subsystem is shown in Table 9. 

Mass is 0.5 kg and the cost is $23. 

Table 9- BOM Excess Flow Valve Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 02 01 High Pressure Lock-Off Valve (HPLV) Sub-Subsystem 1 3.676 20 02 01

20 02 02 Safety Relief Valve Sub-Subsystem 1 1.004 20 02 02

20 02 03 Excess Flow Valve Sub-Subsystem 1 0.463 20 02 03 $23

20 02 03 Excess Flow Valve 1 0.463 CIMG0053 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 38

4.4. Purge Sub-Subsystem 

Figure 28 shows all components included in the Purge Sub-Subsystem. All fuel lines 

are seamless 316 stainless steel. The flex hose is stainless steel jacketed PTFE. The 

T and elbow fittings are forged 316 stainless steel. 

Figure 28- Purge Sub-Subsystem – Components. 

(Source: FEV, Inc. photos)

The bill of materials for the Purge Sub-Subsystem is shown in Table 10. Mass is 1.5 kg 

and the cost is $47. 

Table 10- BOM Purge Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 02 04 Purge Sub-Subsystem 1 1.460 20 02 04 $47

20 02 04 Line, Over temperature Relief 1 0.122 CIMG0037

20 02 04 Elbow, Over temperature Relief 1 0.102 CIMG0038

20 02 04 Hose, Pressure Relief 1 0.256 CIMG0046

20 02 04 Tee, Pressure/Temperature Relief 1 0.112 CIMG0047

20 02 04 Line, Pressure Relief, Tee to Tee 1 0.093 CIMG0048

20 02 04 Purge Line, CNG 1 0.128 CIMG0019

20 02 04 Line, Solenoid to Purge Tee 1 0.466 CIMG0050

20 02 04 Tee, Box, Purge 1 0.181 CIMG0061 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 39

5. High Pressure Circuit Subsystem

5.1. Filler (Refueling) Sub-Subsystem 

Figure 29 shows all the components included in the Filler Sub-Subsystem. 

Figure 29- Filler Sub-Subsystem – Components 

(Source: FEV, Inc. photos) 

Figure 30 is an exploded view of the fill port (NGV1) mechanism. The body of the fill 

port is constructed of stainless steel. The mounting cup for the fill port is injection 

molded plastic. 

Figure 30- Fill Port – Exploded View 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 40

The bill of materials for the Filler (Refueling) Sub-Subsystem is shown in Table 11. 

Mass is 0.6 kg and the cost is $21. 

Table 11- BOM Filler (Refueling) Sub-Subsystem 

QTY Cost

Mass Photo

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732 #REF!

20 03 01 Filler (Refueling) Sub-Subsystem 1 0.637 20 03 01 $21

20 03 01 Directional Valve, Tank Fill 1 0.146 CIMG0006

20 03 01 Fill Port, CNG 1 0.242 CIMG0013

20 03 01 Retainer, Fill Port, CNG 1 0.054 CIMG0014

20 03 01 Screw, Fill Port, CNG 3 0.002 CIMG0015

20 03 01 Fill Cap, CNG 1 0.015 CIMG0017

20 03 01 Line, CNG, Fill to Directional Valve 1 0.178 CIMG0005 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 41

5.2. Distribution, High Pressure Sub-Subsystem 

Figure 31 shows all components included in the Distribution, High Pressure SubSubsystem. All lines are seamless stainless steel (ASTM-213). The elbow and ball 

valve are stainless steel as well. Bracket costs were estimated using progressive metal 

stamping for high volume production. 

Figure 31- Distribution, High Pressure Sub-Subsystem 

(Source: FEV, Inc. photos)

The bill of materials for the Distribution, High Pressure Sub-Subsystem is shown in 

Table 12. Mass is 2.4 kg and the cost is $64. 

Table 12- BOM Distribution, High Pressure Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 03 01 Filler (Refueling) Sub-Subsystem 1 0.637 20 03 01

20 03 02 Distribution, High Pressure Sub-Subsystem 1 2.387 20 03 02 $64

20 03 02 Line, CNG, Directional Valve to Shut off 1 0.140 CIMG0007

20 03 02 Line, Solenoid to Box 1 0.388 CIMG0049

20 03 02 Elbow, Box, Outlet 1 0.150 CIMG0060

20 03 02 Bracket, Fuel Line, Tank to Regulator, CNG 1 0.207 CIMG0228

20 03 02 Fuel Line, Tank to Regulator, CNG 1 1.151 CIMG0227

20 03 02 Line, Filter to Regulator 1 0.144 CIMG0222-2

20 03 02 Shut Off Valve, CNG 1 0.207 CIMG0018 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 42

5.3. Filter Sub-Subsystem 

Figure 32 represents the Filter Sub-Subsystem. 

Figure 32- Filter Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

Figure 33 shows an exploded view of the CNG filter. The upper and lower black 

anodized housings are billet machined; however forging was assumed for high volume 

production of the pressure vessel. The filter is a ‘coalescing element composed of an 

epoxy saturated, borosilicate glass microfiber tube surrounded by a coarse fiber drain 

layer retained by a synthetic fabric safety layer.’ (www.parker.com) The O-rings are 

Buna-N and the plastic filter internal components are Acetal plastic. 

Figure 33- CNG Filter – Exploded View 

(Source: FEV, Inc. photos) 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 43

The bill of materials for the Filter Sub-Subsystem is shown in Table 13. Mass is 0.6 kg 

and the cost is $18. 

Table 13- BOM Filter Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 03 01 Filler (Refueling) Sub-Subsystem 1 0.637 20 03 01

20 03 02 Distribution, High Pressure Sub-Subsystem 1 2.387 20 03 02

20 03 03 Filter Sub-Subsystem 1 0.613 20 03 03 $21

20 03 03 Filter 1 0.613 CIMG0223

20 03 03 Bolt, Filter 2 0.030 CIMG0224 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 44

5.4. Pressure Regulator Sub-Subsystem 

Figure 34 shows all the components included in the Pressure Regulator SubSubsystem including the bracket, guard, fasteners, regulator, and ground strap. 

Figure 34- Pressure Regulator Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

Figure 35 shows an exploded view of the CNG regulator. The unit produced by GFI is 

a single stage regulator. It features coolant heating, integral high pressure solenoid 

shut-off, pressure and temperature transmitters. The upper and lower housings are 

both die cast. A variety of manufacturing processes are used in creating the internals 

including wire forming, machining, injection molding and stamping. Cost considerations 

were made for stringent cleanliness requirements needed for this application. 

Figure 35- Pressure Regulator – Exploded View 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 45

The bill of materials for the Pressure Regulator Sub-Subsystem is shown in Table 14. 

Mass is 4.1 kg and the cost is $78. 

Table 14- BOM Pressure Regulator Sub-Subsystem 

6. Low Pressure Circuit Subsystem

6.1. Distribution, Low Pressure Sub-Subsystem 

Figure 36 shows all components included in the Low Pressure Distribution SubSubsystem including the brackets used for line mounting. Lines used for CNG transport 

are either stainless steel or braided stainless steel reinforced flex lines. Coolant transfer 

hoses for the pressure regulator heating circuit are SAE20R3 and the regulator vacuum 

reference hoses are SAE30R7. 

QTY Cost

Mass Photo

0 - Top Level

12345678910 Total Mass (Unit Mass x qty.) "kg"

Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 03 01 Filler (Refueling) Sub-Subsystem 1 0.637 20 03 01

20 03 02 Distribution, High Pressure Sub-Subsystem 1 2.387 20 03 02

20 03 03 Filter Sub-Subsystem 1 0.613 20 03 03

20 03 04 Pressure Regulator Sub-Subsystem 1 4.095 20 03 04 $78

20 03 04 Ground Strap, CNG Regulator 1 0.061 CIMG0221

20 03 04 Regulator Assembly, CNG 1 1.480 CIMG0222-3

20 03 04 Fasteners, Regulator Assembly, CNG 2 0.027 CIMG0225

20 03 04 Bracket, Regulator, CNG 1 1.184 CIMG0238

20 03 04 Guard, Regulator, CNG 1 1.306 CIMG0239

20 03 04 Nuts, CNG Regulator Bracket 3 0.037 CIMG0240 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 46

Figure 36- Distribution, Low Pressure Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

The bill of materials for the Distribution, Low Pressure Sub-Subsystem is shown in

Table 15. Mass is 4.6 kg and the cost is $109. 

Table 15- BOM Distribution, Low Pressure Sub-Subsystem

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 04 00 Low Pressure Circuit Subsystem 1 8.622 #REF!

20 04 01 Distribution, Low Pressure Sub-Subsystem 1 4.621 20 04 01 $109

20 04 01 Line Cluster, CNG Regulator 1 3.027 CIMG0202

20 04 01 Bracket, Rear, Line Cluster, CNG Regulator 1 0.396 CIMG0250

20 04 01 Bracket, Mid, Line Cluster, CNG Regulator 1 0.721 CIMG0251

20 04 01 Bracket, Front, Line Cluster, CNG Regulator 1 0.177 CIMG0252

20 04 01 Line, Regulator to Fuel Rail 1 0.300 CIMG0222-1 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 47

6.2. Fuel Rails Sub-Subsystem 

Figure 37 shows the Fuel Rail Sub-Subsystem partially disassembled. The fuel injector 

has been removed from the assembly to be included in its own sub-system. The wide 

upper rail shown in the top center of the image supplies the fuel injector. The lower rail 

shown center right of image is a shorter rail that is fed from the injector. The CNG flow 

path then travels through a barbed fitting to a rubber hose and finally to an intake 

manifold mounted nozzle shown in Figure 38. The nozzle is a straight thru diameter 

with no specialized geometry. 

Figure 37- Fuel Rails Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

Figure 38- Injector Nozzle – Components 

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 48

The bill of materials for the Fuel Rail Sub-Subsystem is shown in Table 16. Mass is 3.8 

kg and the cost is $74. 

Table 16- BOM Fuel Rails Sub-Subsystem 

6.3. Fuel Injector Sub-Subsystem 

Figure 39 shows all components included in the Fuel Injector Sub-Subsystem. One (1) 

CNG injector is used for each cylinder. 

Figure 39- Fuel Injector Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 04 00 Low Pressure Circuit Subsystem 1 8.622

20 04 01 Distribution, Low Pressure Sub-Subsystem 1 4.621 20 04 01

20 04 02 Fuel Rails Sub-Subsystem 1 3.825 20 04 02 $74

20 04 02 Bolt, Fuel Rail, CNG 1 0.077 CIMG0215

20 04 02 Fuel Rail Assembly, CNG 1 3.748 CIMG0216 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 49

CNG rail pressure is 90-110 psig. In comparison, gasoline fuel injector rail pressure is

approximately 55 psig. Lower energy density of CNG requires a higher flow rate. The 

construction of the CNG injector is very similar to a gasoline injector with a cost 

premium for non-lubricated fuel operation. Figure 40 shows a cross section of the CNG 

injector. 

Figure 40- CNG Fuel Injector – Sectioned 

(Source: FEV, Inc. photos)

The bill of materials for the Fuel Injectors Sub-Subsystem is shown in Table 17. Mass 

is 0.2 kg and the cost is $95. 

Table 17- BOM Fuel Injectors Sub-Subsystem

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 04 00 Low Pressure Circuit Subsystem 1 8.622

20 04 01 Distribution, Low Pressure Sub-Subsystem 1 4.621 20 04 01

20 04 02 Fuel Rails Sub-Subsystem 1 3.825 20 04 02

20 04 03 Fuel Injectors Sub-Subsystem 8 0.176 CIMG0216-7 $95

20 04 03 Fuel Injector 8 0.176 CIMG0216-7 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 50

7. Controls Subsystem

7.1. Control Module Sub-Subsystem 

All components associated with the Control Module Sub-Subsystem are identified in 

Figure 41. From left to right are the ECU mounting bracket, ECU, Intake Air 

Temperature module and Fuel Pump module. The Silverado CNG system utilizes a 

separate ECU. 

Figure 41- Control Module Sub-Subsystem – Components 

(Source: FEV, Inc. photos)

Figure 42 shows the interior of the CNG ECU including both die cast covers, seal, 

board and fasteners. 

Figure 42- CNG ECU – Exploded View 

(Source: FEV, Inc. photos)

ECU circuitry was reviewed in detail. Each board component was identified and costed 

individually including assembly cost. Figure 43 and Figure 44 show top and bottom 

views of ECU board with number labels matching the table with circuit description. 
Analysis Report BAV-P310324-03

June 26, 2015 

Page 51

Figure 43- CNG ECU Board with Circuit ID numbers – Top

(Source: FEV, Inc. photos)
Analysis Report BAV-P310324-03

June 26, 2015 

Page 52

Figure 44- CNG ECU Board with Circuit ID numbers – Bottom 

(Source: FEV, Inc. photos)

The bill of materials for the Control Module Sub-Subsystem is shown in Table 18. Mass 

is 3.7 kg and the cost is $232. 

Table 18- BOM Control Module Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 04 00 Low Pressure Circuit Subsystem 1 8.622

20 05 00 Controls Subsystem 1 6.488

20 05 01 Control Module Sub-Subsystem 1 3.688 20 05 01 $232

20 05 01 ECU, CNG 1 0.917 CIMG0088

20 05 01 Bracket, CNG Controller 1 2.210 CIMG0141-1

20 05 01 Fasteners, ECU & CNG controller bracket 1 0.054 CIMG0141-3

20 05 01 Fuel Pump Module, CNG 1 0.273 CIMG0236

20 05 01 Intake Air Tempurature (IAT) Module 1 0.234 CIMG0141-2 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 53

7.2. Wire Harnesses Sub-Subsystem 

Figure 45 shows the components comprising the Wire Harness Sub-Subsystem, main 

harness shown left and rearward harness shown right. Both harnesses are dedicated to 

the CNG system. The main harness connects the ECU, IAT module, regulator and 

injectors. The rear harness connects the main harness, fuel pump, fuel pump module, 

as well as high pressure safety lock off connections. 

Figure 45- Wire Harness Sub-Subsystem 

The bill of materials for the Wire Harnesses Sub-Subsystem is shown in Table 19. 

Mass is 2.8 kg and the cost is $71. 

Table 19- BOM Wire Harnesses Sub-Subsystem 

QTY Cost

Mass Photo

0 - Top Level

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Catalog 

Picture 

Reference 

Numbers

20 00 00 Compressed Natural Gas System 239.334

20 01 00 Storage Subsystem 1 209.889 20 01

20 02 00 Safety Devices Subsystem 1 6.603

20 03 00 High Pressure Circuit Subsystem 1 7.732

20 04 00 Low Pressure Circuit Subsystem 1 8.622

20 05 00 Controls Subsystem 1 6.488

20 05 01 Control Module Sub-Subsystem 1 3.688 20 05 01

20 05 02 Wire Harnesses Sub-Subsystem 1 2.800 20 05 02 $71

20 05 02 Wire Harness, CNG System 1 2.091 CIMG0217

20 05 02 Wire Harness, CNG Rear 1 0.709 CIMG0241 Quantity

Unit Cost

Part Numbering Part Name/Description Attribute Data System Subsystem Sub-Subsystem System Subsystem Sub-Subsystem

Product Structure
Analysis Report BAV-P310324-03

June 26, 2015 

Page 54

8. Cost Summary and Conclusion

The primary project objective was to determine net incremental direct manufacturing 

costs (NIDMC) for a complete Compressed Natural Gas (CNG) fuel system. The 

system selected to represent the light-duty pickup truck segment was a 2013 Chevrolet 

Silverado equipped with the bi-fuel option. A NIDMC of $2,276 (Table 20) represents 

the calculated cost to the OEM to add a CNG fuel system to an existing gasoline 

vehicle. The boundary conditions for the cost analysis included manufacturing in the 

United States, high production volume, and a mature and competitive market place. 

Not included in the NIDMC are OEM indirect costs such as corporate overhead, 

research and develop, and tooling (incremental tooling provide separately in Appendix 

A). In addition, there is no OEM profit included in the calculation. Both OEM indirect 

costs and profit are added to the FEV calculated NIDMC using an EPA Indirect Cost 

Multiplier (ICM). The application of the multiplier was outside the scope of this project. 

Table 20 - CNG Subsystem Cost Summary Overview

Subsystem

Total Direct 

Manufacturing 

(i.e., material, 

labor and 

manufacturing 

overhead)

Total Markup 

Cost (i.e., end 

item scrap, 

SG&A, Profit, 

ED&T/R&D)

Total 

Packaging 

Cost

Net 

Incremental 

Direct 

Manufacturing 

Cost

Storage $1,175 $177 $9 $1,360

Safety Devices $126 $24 $1 $151

High Pressure 

Circuit

$154 $28 $3 $184

Low Pressure 

Circuit

$268 $38 $2 $278

Controls $268 $35 $1 $303

TOTAL $1,959 $302 $15 $2,276

Additional cost details for each subsystem listed in Table 20 can be found in Appendix 

A. As highlighted in Figure 46, the largest contributor to the overall CNG system cost is 

the storage system at 60% of the total NIDMC.
Analysis Report BAV-P310324-03

June 26, 2015 

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Figure 46- CNG Subsystems 

Material cost makes up $1531.20 of the total $2276.20 for the CNG system, most of 

which comes from the carbon-fiber wrapped fuel tank. See Figure 47 for a detailed 

breakdown. 

Figure 47- Manufacturing and Mark-up Cost 

All costs were developed using a volume assumption of 450,000 units per year. This 

cost analysis is inclusive of all associated assembly cost from component to vehicle. 

Calculations were performed to determine equipment sizing, cycle times and material 

usage requirements. FEV utilized its extensive database of rates for equipment, labor, 
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material, end item scrap, selling, general and administrative (SG&A), profit, and 

engineering, design and testing (ED&T) to develop costs representative of what an 

OEM would incur for such a system in high volume automotive manufacturing. 

Costs were developed for all critical components by detailing each operation in a 

Manufacturing Assumptions Quote Sheet (MAQS). Process calculators were used to 

determine equipment size and corresponding rate ($/hr), cycle time (seconds) and 

material usage (kg). For example, the Pressure Regulator Cap was identified as an 

aluminum die casting. The number of slide pulls, cavities, part width, part height, 

average wall thickness, parting line area, cavity surface area, and max wall thickness 

were all used to determine the die-casting machine size, cycle time and material usage. 

This information was then transferred to the MAQS where rates are pulled in for 

material, labor, manufacturing overhead/burden, end item scrap, SG&A, profit, and 

ED&T. Cost contributions are then calculated for these core cost elements. Similar 

process calculators are used for subsequent processing such as machining, where all 

machine features are measured, speed and feed rates assigned based on the 

respective material, and feed times calculated. In addition pallet changes, tool changes, 

rapid times, as well as estimated work pieces per fixture are used to estimate the total 

cycle time. Finally all processes are summed, end item packaging estimated, and total 

cost calculated. Cost contributions for the core cost elements are then linked to the 

Cost Model Analysis Template (CMAT). The CMAT incorporates cost data from various 

Sub-Subsystems into one summary sheet. For detailed cost breakdown, see Appendix 

A. 

Overall system costing methods are either calculated or commodity. All fastening 

hardware (bolts, washers, nuts, etc...) come from online bolt manufacturer’s pricing. 

Commodity pricing was also used on small components within larger assemblies such 

as the ECU circuits and components within assemblies like the pressure regulator. For 

example commodity pricing was referenced to estimate costs for components like 

springs, seals, solenoids, and diaphragms. 
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9. Appendix A

The CNG system level cost summary, by major components and assemblies, is shown below in Table 21. 

Table 21 - Complete Cost Summary (CMAT) – CNG System