COORDINATING RESEARCH COUNCIL, INC. 

3650 MANSELL ROAD·SUITE 140·ALPHARETTA, GA 30022

CRC Report No. E-77 

Vehicle Evaporative 

Emission Mechanisms: 

A Pilot Study 

June 24, 2008 
 

 

The Coordinating Research Council, Inc. (CRC) is a non-profit 

corporation supported by the petroleum and automotive 

equipment industries. CRC operates through the committees 

made up of technical experts from industry and government who 

voluntarily participate. The four main areas of research within 

CRC are: air pollution (atmospheric and engineering studies); 

aviation fuels, lubricants, and equipment performance, heavyduty vehicle fuels, lubricants, and equipment performance (e.g., 

diesel trucks); and light-duty vehicle fuels, lubricants, and 

equipment performance (e.g., passenger cars). CRC’s function is 

to provide the mechanism for joint research conducted by the two 

industries that will help in determining the optimum combination 

of petroleum products and automotive equipment. CRC’s work 

is limited to research that is mutually beneficial to the two 

industries involved, and all information is available to the public. 

CRC makes no warranty expressed or implied on the application 

of information contained in this report. In formulating and 

approving reports, the appropriate committee of the 

Coordinating Research Council, Inc. has not investigated or 

considered patents which may apply to the subject matter. 

Prospective users of the report are responsible for protecting 

themselves against liability for infringement of patents.
A Report on 

Vehicle Evaporative Emission Mechanisms:

A Pilot Study

CRC Project E-77 

June 24, 2008 

Submitted by 

Harold M. Haskew PE 

Thomas F. Liberty 

Harold Haskew & Associates, Inc. 

Milford, Michigan 
 

ii

Acronyms

ATL............... Automotive Testing Laboratories 

CRC............... Coordinating Research Council, Inc. 

FID ................ Flame Ionization Detector 

HC ................ Hydrocarbon 

HH&A........... Harold Haskew & Associates 

LA-92 ............ Unified Driving Cycle 

MTBE............ Methyl Tertiary Butyl Ether 

NBR .............. Nitrile Rubber or Acrylonitrile Butadiene Rubber 

PFI................. Port Fuel Injection 

RL SHED ...... Running Loss Sealed Housing for Evaporative Determination 

RVP............... Reid Vapor Pressure 

SHED ............ Sealed Housing for Evaporative Determination 

VT SHED...... Variable Temperature Sealed Housing for Evaporative Determination 
 

iii

Table of Contents

Background ...................................................................................................................... 1 

Discussion ........................................................................................................................ 2 

 Project Timing......................................................................................................... 3 

 Vehicle Selection and Procurement ........................................................................ 3 

 Fuels and Test Parameters....................................................................................... 4 

 Pre-Test Stabilization on the Test Fuel ................................................................... 4 

 The Test Concept .................................................................................................... 5 

 Permeation .............................................................................................................. 5 

 Tank Vapor Venting.......................................................................................... 5 

 Leaks ....................................................................................................................... 6 

 A Test Method for Separating Permeation from Tank Venting and Leaks ............ 6 

 Examples of Measurements .................................................................................... 9 

 Static Permeation and Leak Test.................................................................... 9 

 Dynamic (Running Loss) and Hot Soak Test .............................................. 11 

 The Running Loss Driving Cycle ................................................................ 13 

 Diurnal Testing......... ................................................................................ 15 

The Issue of Non-Fuel Emissions .................................................................................. 23 

An Overview of What Was Learned.............................................................................. 27 

Acknowledgements........................................................................................................ 28 

Appendix I...................................................................................................................... 29 

Appendix II .................................................................................................................... 33 
 

iv

List of Figures

Figure Description Page

1 Control System Schematic ....................................................................... 5 

2 Sealed Housing for Evaporative Determination ...................................... 6 

3 Trap Canister............................................................................................ 6 

4 Static Test - Pressurization....................................................................... 7 

5 Static Test – Fuel Pump Energized .......................................................... 8 

6 Static Test Results.................................................................................... 9 

7 Static Permeation – Implanted Leak ...................................................... 10 

8 Running Loss SHED.............................................................................. 12 

9 Running Loss Driving Cycle.................................................................. 13 

10 Dynamic Test Results ............................................................................ 14 

11 Dynamic Test Results – All Ten Vehicles ............................................. 14 

12 Three Day Diurnal Permeation .............................................................. 16 

13 Temperature and RVP Effects ............................................................... 17 

14 Low Temperature Diurnal – 7 psi Fuel.................................................. 18 

15 High Temperature Diurnal – 7 psi Fuel ................................................. 18 

16 Low Temperature Diurnal – 9 psi Fuel.................................................. 19 

17 High Temperature Diurnal – 9 psi Fuel ................................................. 19 

18 Canister Breakthrough ........................................................................... 20 

19 Canister Breakthrough ........................................................................... 21 

20 Hose Configurations .............................................................................. 22 

21 Canister Vent Hose – Vehicle Installation............................................. 23 

22 Non-Fuel Emissions............................................................................... 24 

23 Non-Fuel Component Permeation ......................................................... 24 

24 Non-Fuel Effects on High Temperature Diurnal ................................... 25 

25 Non-Fuel Effects on Low Temperature Diurnal .................................... 25 

26 Non-Fuel Component Permeation ......................................................... 26 

27 Blank SHED Test .................................................................................. 29 

28 Blank SHED Test Set-up ....................................................................... 30 

29 Blank SHED Test Results – SHED 14................................................... 30 

30 Blank SHED Test Results – SHED 15................................................... 31 

31 Trap Canister Emissions – Blank SHED Test ....................................... 31 

 32 Repeat of Figure 12-Three Day Diurnal Permeation... ................... 32 

List of Tables

Table Description Page

1 CRC E-77 Pilot Study Test Fleet .............................................................. 3 

2 CRC E-77 Permeation Pilot Study Tests ................................................. 15 

3 Diurnal Vapor Generation........................................................................ 21 
 

1

Vehicle Evaporative Emission Mechanisms: A Pilot Study 

BACKGROUND 

The Coordinating Research Council, Inc. (CRC) has sponsored a variety of timely vehicle 

evaporative emission test programs over the last two decades, adding greatly to the knowledge 

base of mobile-source inventory issues. Included in the research were the: 

• Auto-Oil Hot Soak Pilot Study (1993) 300 vehicles 

• CRC E-9 Real-Time Diurnal Study (1996) 150 vehicles 

• CRC E-35 Running Loss Study (1997) 150 vehicles 

• CRC E-41 Late Model In-Use Evap Emissions (1998) 50 vehicles 

CRC Project E-41 examined the evaporative emissions of fifty 1992 to 1997 model year 

vehicles. Six of the vehicles were certified to the federal “Enhanced Evaporative Emission” 

standards, but were tested at low age and miles. The U. S. enhanced evaporative emissions 

requirements were phased in nationally, starting with the 1996 model year vehicles, with full 

implementation by the 2000 model year. These requirements had a major impact on the design 

and content of the systems used for evaporative emissions control. CRC Project E-41 

concluded that the six newer vehicles tested performed well against their respective Enhanced 

Evaporative emissions certification requirements, but suggested that a similar study be 

conducted after this class of vehicles had aged. 

In 2004, CRC committee members recommended a follow-up study to investigate the in-use 

performance of the “enhanced evaporative emission” fleet after it had accumulated age and 

miles. The committee discussed the best way to conduct such a study. Determining the 

vehicle’s total evaporative emission rates is of interest, but the measurements should also be 

focused on isolating the parameters useful for modeling. This was not to be a “compliance” 

program. 

Vehicles are certified by demonstrating emission performance at levels below published limits. 

For vehicle evaporative emissions, there are tests that measure three modes of vehicle 

operation: 

1. Running Losses 

2. Hot Soaks 

3. Diurnal Emissions 

Certification tests, which are performed under specific conditions with tightly controlled 

parameters, may represent extreme conditions of temperature and duration. The running loss 

test, for example, consists of a single drive lasting more than one hour, certainly longer than the 

typical urban trip. 

Inventory modelers have used information from the certification tests to help estimate the 

contribution of vehicle emissions to the atmosphere, but more information is needed to 

determine the emission rates at different temperatures, different trip lengths, and with different 

fuels. In 2005, EPA contracted Harold Haskew & Associates, Inc. to suggest a different 

approach for gathering the data necessary to model evaporative emissions. The resulting report, 

“A New Approach to Modeling On-Road Vehicle Evaporative Emissions,” was published June 

2, 2005. This new approach suggested measuring the mechanisms of evaporative emissions, 

instead of the modes. 
 

2 

The mechanisms were defined as: 

• Leaks 

• Diurnal displacement vapors 

• Permeation 

Diurnal vapors and permeation were thought to be functions of ambient and vehicle 

temperature and fuel composition. Emissions from leaks are not thought to be a property of the 

fuel. The challenge was to invent a procedure or test that would allow the separation of leaks 

from diurnal vapors and leaks from permeation. Characterization of the emission mechanisms 

of the fleet could lead to more informed estimates of the evaporative emission rates at various 

temperatures, with different fuels, and driving conditions. 

A separate CRC Project, E-65, “Fuel Permeation from Automotive Systems,” measured and 

reported the permeation of ten different vehicle fuel systems with three different gasolines. 

This project vented the tank vapor emissions outside the VT-SHED to allow an independent 

measurement of permeation. That experience suggested that it should be possible to measure 

both permeation and the tank venting loss during a real-time (24 hour) diurnal event, if a 

separate trap canister was placed outside the VT-SHED and the vehicle’s canister loss 

collected. 

CRC Project E-77 evolved as a pilot study to determine if the mechanisms of evaporative 

emissions could be measured effectively. If the pilot study were a success, a follow-on program 

could continue to develop additional data, suitable for input to current and proposed inventory 

models, which could assist in modeling current and future mobile-source emissions. This work 

is timely as this category of newer vehicles will become the predominant class of vehicles in 

the light-duty fleet. 

This report focuses on the process of measuring emission mechanisms and the lessons learned 

to date. Plots of the test data are presented in this report’s appendix. The raw data are available 

in MS Excel® format from the CRC website (www.crcao.org). 

DISCUSSION 

There were a number of elements involved in this pilot study. 

• Project timing 

• Vehicle selection and procurement 

• Fuels and test parameters 

• Pre-test stabilization on the test fuel 

• The test concept: measuring leaks, permeation, and diurnal vapor losses 

• Examples of measurements 

• Non-fuel emissions 

• Overview of what was learned 
 

3

Project Timing - The first draft proposal was considered by CRC in May 2004, emphasizing 

the need for follow-up to Project E-41 given the accumulation of time and miles by enhanced 

evaporative control vehicles. A request for proposals was issued in October 2005. HH&A’s 

proposal was based on the use of new concepts to measure the “mechanisms” of evaporative 

emissions, rather than conventional “certification-type” tests. HH&A was awarded the contract 

in February 2006 for a “Pilot Study of Ten Vehicles” to investigate this new concept. Data 

collecting began in early July 2006 and ended in early 2007. 

Vehicle Selection and Procurement - Nine vehicles were recruited from the Phoenix area. 

One vehicle (Vehicle 6, a 1996 Chevrolet Cavalier) was tested twice. It was tested the second 

time with an implanted leak in the fuel cap to represent a “leaker” (renumbered Vehicle 7). 

The sample was not intended to represent the entire in-use fleet, but rather a small sample 

distributed between makes, models, and technologies. 

The test vehicles came from a population that was comprised almost entirely of port fuel 

injection models with in-tank fuel pumps. The test procedures would have to be modified if 

older, carbureted, or advanced design new vehicles were included. 

The following mix, certified for sale in all fifty states (i.e., meeting both federal and California 

evaporative emission standards) was chosen: 

• Three 1990-1995 MY vehicles certified to Pre-Enhanced standards 

• Five 1996-2000 MY vehicles certified to Enhanced standards 

• One 2007 MY vehicle certified to the new Tier II standards 

Table 1 - CRC E-77 Pilot Study Test Fleet 

Vehicle 

Number 

Model 

Year Make Model 

Eng. 

Size 

L. 

Fuel 

System 

Odo. 

Miles 

Tank 

Size 

Gallons 

Fuel Tank 

Material 

Pre-Enhanced Evap

3 1992 Honda Accord 2.2 PFI 71,129 17.0 Metal 

10 1992 Toyota Camry 2.2 PFI 162,838 18.5 Metal 

9 1995 Plymouth Neon 2.0 PFI 106,220 11.2 Metal 

Enhanced Evap

1 1996 Chevrolet S-10 4.3 PFI 68,420 19.0 Metal 

6 1996 Chevrolet Cavalier 2.2 PFI 112,768 15.3 Metal 

7 1996 Chevrolet Cavalier (w/leak) 2.2 PFI 113,125 15.3 Metal 

8 1996 Ford Explorer 4.0 PFI 114,822 21.0 Metal 

4 1999 Dodge Grand Caravan SE 3.3 PFI 98,765 20.0 Plastic 

2 2000 Toyota Tacoma 3.4 PFI 80,557 15.1 Metal 

Tier II (near zero)

5 2007 Ford Taurus 3.0 PFI 6,916 18.0 Metal 
 

4 

Candidate owners were offered incentives to participate in the program. The incentives were 

the use of a loner car (a pre-paid rental vehicle) and free fuel during the vehicle preconditioning and the vehicle test period. The test plan required having the owner drive the 

selected (and committed) vehicle for a minimum of four weeks on ethanol-free road fuel before 

the vehicle was submitted for testing. Vehicle owners signed an agreement to use only fuel 

provided by the laboratory for the four-week minimum period prior to testing. Unlimited fuel 

fills were permitted during normal working hours. During non-working hours and weekends, 

owners were permitted to contact laboratory personnel to obtain any needed additional fuel. 

Fuel usage for each vehicle fill was logged and compared to accumulated odometer readings to 

validate that the fuel usage and mileage accumulation were in order. No discrepancies were 

noted during the pilot study. 

Initial screening included a review of the emission sticker to determine the certification 

category and documentation of the make, model year, engine family, evaporative family, and 

accumulated odometer reading. The owner was asked if the vehicle had undergone collision 

repairs or had recently been repainted. New tires and paint emit at an unrepresentative rate, and 

were excluded from the program. The tires on each vehicle were visually inspected, and the 

purchase date of obviously new tires was determined. The engine compartment was inspected. 

Signs of collision repair and/or engine modifications were noted. Tampering, extreme odometer 

readings, and/or unusual equipment configurations were excluded. A final inspection looked 

for any unusual hydrocarbon odors or signs of spills. All exceptions were resolved prior to 

acceptance of a particular candidate. 

Testability issues were also noted during this initial inspection. Tire conditions, cooling 

systems, brakes, and exhaust systems were inspected to insure the vehicle could be successfully 

tested. All vehicles had accumulated at least 4,000 miles (a project requirement) prior to 

entering the test program. ATL’s Project Manager reviewed each specific recommended 

candidate with the HH&A Program Director prior to final acceptance. 

Fuels and Test Parameters - The statement of work specified that the pilot study focus on a 

non-oxygenated (E0) fuel at two volatility levels, 7 and 9 psi RVP. CRC supplied the fuel for 

the project at 7 psi volatility. The laboratory added butane to the base fuel for the 9 psi 

evaluation. 

The test temperature for the static and dynamic tests was 86oF. This is approximately the 

average temperature of the Federal (72o to 96oF) and California (65o to 105oF) diurnal 

certification tests, and a typical temperature for a summer day. 

The diurnal test temperature range was specified at two levels, 65o to 105oF (the California 

certification specification), and a higher temperature range, 85o to 120oF (representing a severe 

temperature day). 
 

5

Pre-Test Stabilization on the Test Fuel - Many areas of the United States were required to 

use an oxygenated fuel to improve vehicle emissions, especially during the summer season. 

While MTBE was the most common oxygenate, ethanol was also used. Project E-65 

demonstrated that the permeation of vehicle fuel systems increased with the use of fuels 

containing ethanol, compared to fuels with MTBE, or no oxygenate. Project E-65 also 

demonstrated that if ethanol had been used, it could take two to four weeks for the ethanol 

increase to dissipate. With that in mind, the design of the pilot program required that vehicles 

be operated for four or more weeks with a known oxygenate-free fuel before starting the test 

sequence. 

The Test Concept: Measuring Leaks, Permeation and Diurnal Vapor Losses - This pilot 

study evaluated the use of a new methodology for understanding and quantifying vehicle 

evaporative emission rates. This new concept partitions and assigns the vehicle’s contribution 

to the evaporative emission inventory into three mechanisms: 

1. Permeation 

2. Tank vapor venting 

3. Leaks (with two subsets - Liquid and Vapor) 

Permeation is the migration of HC through the various elastomers in a vehicle fuel system1

. 

Permeation rate is strongly affected by the material’s temperature, doubling for each 10oC 

(18oF) increase in the range of normal summer temperatures. It is also strongly affected by 

gasoline composition, especially with ethanol-containing fuels. 

Tank vapor venting emissions are controlled by fitting a carbon canister to the atmospheric tank 

vent. Figure 1 is a schematic of a typical early control system. During a daily heating period, 

the temperature of the vehicle’s fuel tank increases, forcing HC vapors from the tank. Excess 

emissions, exceeding the carbon canister’s capacity, are vented to the atmosphere. 

Figure 1 - Control System Schematic 

 

1 “Fuel Permeation from Automotive Systems: Final Report CRC Project E-65,” Haskew, Liberty and McClement, September 2004, available 

on the CRC and California Air Resources Board websites. 
 

6 

Leaks can be liquid or vapor. Mass emissions are measured in a VT SHED. The SHED test 

method combines all three emission mechanisms 

(leaks, diurnal venting, and permeation) into a single 

test result. 

The SHED technique2

,

3

 involves placing the vehicle 

in a sealed enclosure (Figure 2), and calculating the 

mass in the enclosure from the volume, density and 

concentration in the enclosure at the start and end of a 

time period. The difference between the mass at the 

start and end of test is the emission rate, e.g., grams 

per unit time. 

 Figure 2 - Sealed Housing for 

 Evaporative Determination 

 

The goals of this pilot study were to determine if the three evaporative emission mechanisms 

could be separated and individually quantified, as well as to provide an indication of how the 

“enhanced evaporative emission” vehicles were performing as they aged. 

Permeation and tank venting losses are strongly driven by fuel composition, ambient 

temperature, and ambient temperature change. Liquid leaks are not strongly affected by normal 

summer temperatures, and are thought to have two components: 

1. Static leaks occurring while the engine is turned off and the vehicle is stationary 

2. Increase in leak rate caused by the system pressure increase during engine operation. 

A Test Method for Separating Permeation from Tank Venting and Leaks - Previous CRC 

Project E-65 had separated the canister loss from the permeation measurement by venting the 

losses from the carbon canister outside the 

SHED. For Project E-77, the canister vent 

losses were collected and measured in a separate 

“trap canister” on a scale outside the SHED, as 

shown in Figure 3. This vent line was capped 

off, i.e., sealed during the Static Test, but 

connected as shown in the figure for the 

Dynamic and the Diurnal Test. The ambient 

temperature in the SHED was constant during 

the static test, and there was no vapor created at 

constant temperature. This vent was closed to 

pressurize the system for the leak evaluations. 

The resulting SHED increase in HC mass was 

 

2

 SAE 891121 “Evaporative Emissions Under Real-Time Conditions.” 

3

 SAE 901110 “The Development of a Real-Time Evaporative Emission Test.” 

Figure 3 - Trap Canister
 

7

permeation4

. The last mechanism that needed to be evaluated was leaks. Leaks can be both 

vapor and liquid. A liquid leak can have significant mass, currently undetected by the vehicle’s 

on-board diagnostic system. Considerable thought and effort have gone into the creation of a 

simple and effective liquid leak detection methodology, without success. The techniques used 

in this project required the use of a SHED for measurements. The techniques were not simple, 

but they proved effective. 

Leaks from the vehicles chosen for this pilot study5 were quantified in a three-step test process. 

The first step was to measure the permeation rate of the vehicle at 86oF. The vehicle was 

allowed to stabilize at 86oF in the SHED and the permeation rate was measured. The 

experience gained was that a vehicle’s permeation rate lies in the 20 to 90 mg/hour range. The 

presence of a static liquid leak is thought to overwhelm this value; such a leak would (or could) 

be apparent by inspection. The second part of the test, looking for pressure driven leaks in the 

vapor system, was performed by pressurizing the vehicle’s tank to 5” H2O through the fuel cap 

and tubing from outside the SHED (Figure 4). The special fuel cap, the hose and the 

pressurization apparatus was installed before the start of the sequence. The HC concentration 

in the SHED was monitored, and the increase in the mass of HC in the SHED was compared to 

the static permeation rate. If there was no (or insignificant) rate of increase, it was deduced that 

no vapor leak is present. 

 

4

 This is a simplification. There are other HC sources present that are not fuel permeation. These include tire, 

paint, adhesives and vinyl emissions, and the possibility of fuel leaks from the fuel injectors. We believe these 

to be a minor component of the emissions measured in this study. 5

 The early and enhanced evaporative emission control vehicles tested had port fuel injected (PFI) engines with 

in-tank fuel pumps and carbon control of venting emissions. 

Figure 4 - Static Test – Tank Pressurization 
 

8 

A final test was to energize the vehicle’s fuel pump and pressurize the system up to and 

including the injectors (Figure 5). If there were a pressure leak in the liquid system, an increase 

in the SHED mass over time would be seen, i.e., the leak would be additive to the permeation 

rate. Example of this test methodology follows. 

Figure 5 - Static Test – Fuel Pump Energized 
 

9

Examples of Measurements – There were three basic tests used in this study; 

1. Static Permeation and Leak Test 

2. Running Loss and Hot Soak Test 

3. Diurnal Tests 

Static 86 F Permeation

Vehicle 1 - 7 PSI

240

242

244

246

248

250

252

254

256

258

260

262

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 8.6 mg/hr (206 mg/day)

Incremental Incr. w/ pressurized tank 3.0 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6875

Figure 6 – Static Test 

The Static Permeation and Leak Test Figure 6 illustrates the test results from one of the pilot 

tests (Vehicle 1 – 1996 Cavalier on 7 psi fuel). The horizontal axis is the test time in minutes, 

and the vertical axis is the calculated HC mass in the SHED in milligrams. The SHED analysis 

system included a Rosemont FID calibrated on propane, but expressed as ppm C1. 

The first 60 minutes of the test were devoted to the static permeation measurement. The 

vehicle was placed6

 in the constant temperature (86°F), allowed to stabilize for an appropriate 

amount of time, and then the test began. At time zero in Figure 6, the SHED mass estimate was 

242 milligrams. The HC concentration in the SHED was recorded every 30 seconds, and the 

mass for that time calculated, using the hot soak SHED calculation method defined in 40 CFR 

§ 86.138-90. The red dots indicate the mass estimate for each of the first 30 minutes of 

measurements. These data were retained but not used in the permeation rate measurement. 

The next 30 minutes of measurement were made in the same fashion, and the time/mass values 

entered in an Excel® file where the “SLOPE” value was returned and became the “static 

 

6

 The vehicle was set up to run two types of leak tests during this test period, the “system pressurization,” and the 

“fuel pump energized.” Both require that the canister (tank) vent be sealed. The procedure used to do this is block 

off the canister’s vent path at the external bulk-head fitting at the SHED wall at the start of the pressurization, and 

throughout the remainder of the test. 
 

10 

permeation rate” for that vehicle and fuel (expressed as an hourly rate). In this example, the rate 

is 8.6 mg/hour. 

At the 60 minute point, the tank was pressurized using the apparatus shown in Figure 4 to 5” 

H2O. This pressure was actively maintained for the next 60 minutes during the “system 

pressure test” and the “fuel pump energized” parts of the leak tests7. The mass results from the 

constant pressure portion of the test from 75 to 90 minutes were used to validate a negative, 

i.e., to document that there was no vapor system leak in the test vehicle. If the time rate of 

emissions measured in the SHED was the same as the previously measured “permeation rate,” 

there was no vapor leak of consequence present in the vehicle at that time. 

During the time period from 90 to 120 minutes (the last 30 minutes of the test period), the 

vehicle’s in-tank fuel pump was externally energized to create pressure in the vehicle’s liquid 

fuel system, up to and including the fuel injectors. 

Static Permeation Test Results with a Leak Present - One of the vehicles was evaluated with an 

implanted leak to see if the test procedures could identify and quantify the impact of a leak. 

The vehicle chosen for this evaluation was Vehicle 6, the 1996 Chevrolet Cavalier. We 

replaced the vehicle’s fuel cap with a similar cap with a 0.02” diameter hole in it. This is a 

common test cap tool used for on-board diagnostics development. The vehicle was renamed as 

Vehicle 7. The static test results are shown in Figure 7 above. 

 

7

 The “actively maintained” comment means that the test operator had to watch and adjust the supply during this 

time period to hold it at the desired level. 

 Figure 7 - Static Permeation- Implanted Leak 

Static 86 F Permeation

Vehicle 7 (with implanted leak) - 7 PSI

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 59.0 mg/hr (1416 mg/day)

Incremental Incr. w/ Fuel Pump 'On' 2417.3 mg/hr

Steady State

Permeation

Power the

Fuel Pump 

Vehicle 06 Test 6963
 

11

The static permeation rate for Vehicle 6 was 26 mg/hour. With the implanted leak, the 

measured value increased to 59 mg/hour. Therefore, the leak added an estimated 33 mg/hour to 

the vehicle emission rate, or more than double the original value. 

The step where the vehicle vapor system is pressurized to 5” H2O was not performed with the 

implanted leak. Forty-five minutes of SHED measurement were used to calculate the static 

performance rate, rather than the 15 minutes used on the other vehicle tests. The plot of the 

measurements indicated that the increase in SHED mass was constant for this period. 

The effect of energizing the fuel pump to pressurize the fuel liquid system gave a dramatic 

increase in the SHED measurement during this period. The increase of 2.3 g/hour was 

attributed to the agitation and heating occurring in the fuel tank as energy was supplied to the 

pump (thought to be in the range of 60 to100 watts) and the return fuel sprayed into the fuel 

vapor space. 

This demonstration confirmed that the pilot test procedure concept could identify vapor leaks. 

Dynamic (Running Loss) and Hot Soak Test - The preceding section addressed the concepts of 

separating the permeation emission rate from the tank venting emission rate, and establishing 

the presence or absence of leaks. The second part of the pilot study included a dynamic test to 

measure the permeation and tank venting emission rate during vehicle operation (“running 

losses”) and the temporary condition following vehicle operation known as the “hot soak.” 

The “dynamic” part of the dynamic test comes from the fact that the vehicle is driven and the 

system temperatures rise during the test. The ambient temperature in the Running Loss SHED 

was held constant at 86°F, while the vehicle’s fuel system temperature rose during the test. 

Two 1435 second (23.9-minute) LA-92 driving cycles were performed during the running loss 

measurements, consecutively, with no soak between. During this period fuel temperature was 

expected to rise on average approximately 18°F above the initial ambient temperature. The 

running loss air handling system includes a proportional speed under-car blower that is slaved 

to dynamometer speed. This apparatus was used during running loss testing with minor tuning 

for specific vehicles. It is, without additional input, capable of reasonable fuel tank 

temperature control. Each vehicle was fitted with a “skin” thermocouple at the front of the 

tank, at approximately the 1/8th fill level to represent the fuel liquid temperature. No attempt 

was made to follow a predefined fuel tank temperature profile (FTTP) in this program. Fuel 

temperatures were recorded, and results are available in the real-time records. 

Vehicle running loss emissions are measured in a special version of a “SHED” known as the 

“Running Loss SHED,” (RL-SHED) (Figure 8), which includes a chassis dynamometer for 

simulating the vehicle driving loads. The vehicle is operated inside this sealed enclosure over 

some chosen driving cycle. The increase in HC emissions inside the enclosure are measured 

and calculated as mass emissions (40 CFR §86.163-96). The execution is complicated by 

several factors, including: 

1. The engine must be supplied with external induction air. 

2. The exhaust must be conducted externally without any leaks. 

3. The load supplied to the vehicle through the chassis dynamometer must not create or 

allow external leaks. 
 

12 

4. The internal SHED temperature must be maintained while sizable heat is rejected to 

the ambient by the running engine and exhaust. 

5. The cooling air supplied to the radiator must be modulated to represent the vehicle’s 

road speed. 

6. The underbody (and especially the fuel system) temperature should represent the rate 

of rise experienced by a real road-drive. 

Canister vent losses were isolated from the permeation emissions using the same technique, by 

venting the carbon canister’s fresh air vent to the outside of the RL-SHED with a leak-tight 

Teflon® hose, where it was connected to a small carbon “trap” canister, on a top-loading 

precision scale. The scale was capable of measuring changes of 0.01 grams (10 milligrams). 

There were no tank venting emissions measured on any of the running loss test measurements. 

All of the vehicles appeared to be actively “purging” the vehicle’s control canister during the 

tests, and drawing fresh air in during the test. If there were any emissions from the vehicle’s 

canister, as might have occurred if there were no vehicle purge, or if very high volatility fuels 

with excessive vapor generation were used, it would have been measured. 

Figure 8 - Running Loss SHED 
 

13

The Running Loss Driving Cycle consisted of two cycles of the “Unified Driving Cycle,” 

otherwise known as the LA-92. A velocity versus time plot is shown in Figure 9. 

The cycle takes 24 minutes to complete, and covers 9.8 miles, with many speed changes. Two 

back-to-back cycles were driven, the first a “cold start,” the second immediately following the 

cold start. The “cold start” condition is usually created by soaking the vehicle for a minimum 

of 18 hours at 86°F, moving it to the stabilized 86°F RL-SHED, making the test connections, 

and then waiting a minimum of one hour before the initial start and run. 

The SHED emissions were measured during the 48+ minutes of engine operation, and then 

continuously for one hour after the engine was turned off. This one hour is the “hot soak” 

period. The total test time is 1 hour and 48 minutes. 

Figure 10 on the next page shows the test results from the 7 psi fuel test on Vehicle 4. The 

horizontal axis is test time in minutes, and the vertical axis is the HC mass measured in the RLSHED during the test period. The SHED mass emissions for the first 48 minutes of the test are 

shown with the green line in the plot. The regression analysis capability in Excel® was used to 

calculate a second order curve to the 96 data points in the 30-second measurements during the 

48 minute drive. That relationship is shown with the black smooth trace through the green line. 

The engine was shut off at the end of the drive, and the analysis system continued to measure 

the HC emissions in the SHED. This represents the “hot soak” portion of the test. 

A comparison plot of the ten vehicle tests are shown in Figure 11 on the next page. 

Figure 9 - RL Driving Cycle 

Unified Cycle (LA-92)

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Test Time - minutes

Speed - mph

Cycle Time (min) 23.9

Maximum Speed (mph) 67.2

Average Speed (mph) 24.6

Average Non-Zero Speed (mph) 29.4

Time @ Zero Speed (%) 16.2

Distance (miles) 9.82
 

14 

Running Loss and Hot Soak

E77 Vehicles

0

500

1000

1500

2000

0 20 40 60 80 100

Test Time - minutes

Cumulative Permeation - mg

Running Loss Hot Soak

Vehicle 1 = 0.017 g/mi

Vehicle 2 = 0.025 g/mi

Vehicle 3 = 0.039 g/mi

Vehicle 4 = 0.009 g/mi

Vehicle 5 = 0.002 g/mi

Vehicle 6 = 0.011 g/mi

Vehicle 7 = 0.012 g/mi

Vehicle 8 = 0.009 g/mi

Vehicle 9 = 0.011 g/mi

Vehicle 10 = 0.069 g/mi

Figure 10 – Dynamic Test Results 

Running Loss and Hot Soak

Vehicle 4 - 7.0 Psi

y = -0.0398x2 + 5.5741x

R2

 = 0.9865

y = -0.0087x2

 + 2.3904x + 104.51

R2

 = 0.9004

0

50

100

150

200

250

300

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25636

Running Loss

Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.009 g/mi

Figure 11 – Dynamic Test Results – All Ten Vehicles 
 

15

Diurnal Testing - The third major element of the pilot program was diurnal testing using the 

external vent for the vehicle’s carbon canister to separate the tank venting emissions from the 

permeation. 

Table 2 - CRC E-77 Permeation Pilot Study Tests 

 Diurnal Tests 

Static Perm 

& Leak 

Tests 

Running 

Loss & Hot 

Soak 

7 psi 

65-105°F 

7 psi 

85-120°F 

9 psi 

65-105°F 

9 psi 

85-120°F 

Pre Enhanced 

Veh 3 Honda Accord 6902 25635 3 day

6915

3 day

6925 

Veh 9 Plymouth 

Neon 6969/6975 25646 6973 6974 

Veh 10 Toyota 

Camry 6977 25648 6983 

 

Enhanced 

Veh 1 S-10 PU 6875 25632 6857 6865 6888 6893 

Veh 2 Tacoma PU 6890 25634 6883. 6904 6896 6899 6929 

Veh 4 Dodge 

Caravan 6912 25636 3 day

6919

3 day

6922

3 day

6926

3 day 

6927

Veh 6 Chevy 

Cavalier 6939 25640 6953 6955 6959 6961 

Veh 7 Cavalier 

w/leak 6963 25642 6964 6966 

Veh 8 Ford Explorer 6949 25641 6954 6956 6957 6962 

 

LEV II 

Veh 5 Taurus Sedan 6923 25638 3 day 

6928/6931

3 day 

6933 

Table 2 shows a summary of the tests performed. The vehicles, classified by the emissions 

standards to which they are certified, are shown on the left side of the table. The numbers in 

the various boxes identify the laboratory’s test ID numbers for the individual tests. In some 

cases, two numbers indicate that repeat tests were conducted. The purpose of this table is to 

indicate the mixture of one and three-day diurnals that were performed, and to indicate the 

vehicles tested on the 9 psi (higher volatility) fuel. 

Immediately following completion of the hot soak test, the vehicle was moved to a VT-SHED 

for diurnal testing. The diurnal SHED was used to soak the vehicle at 65°F overnight. The 

vehicle soaked a minimum of 16 hours before the diurnal test was initiated. Again using 

Project E-65 procedures, the vapor space at the fuel cap and the canister outlet were plumbed to 

the outside of the SHED enclosure. A third well-purged collector canister was used to 

continuously monitor canister outlet emissions. 

The California 65°F–105°F–65°F diurnal temperature profile was used for the baseline test on 

all vehicles, normally terminating after one 24-hour cycle. One of each vehicle group 
 

16 

continued for a total of three 24-hour cycles. Continuous measurements of HC levels, ambient 

conditions, tank weights, and tank temperature were recorded throughout. 

At the end of the baseline diurnal, the SHED was purged and the internal ambient temperature 

was raised to 85°F. The vehicle remained in the enclosure for a minimum of 16 hours. The 

enclosure was purged again, the temperature was allowed to stabilize, and a second diurnal was 

performed. The second diurnal followed an extreme 85°–120°F cycle. This new cycle rose in 

proportion to the California 65°–105°F cycle in the first 9 hours, and then dropped back to 85°F 

over the remaining 16 hours. This is a 35°F temperature change as opposed to the 40°F 

temperature change in the 65°-105° cycle. 

The three vehicles selected for 72-hour tests in the baseline test also received a 72-hour 

extreme diurnal test. All five vehicles certified to enhanced evaporative standards were also 

tested with 9.0 psi RVP fuel. 

Figure 12 shows an example of the diurnal results obtained during the pilot study for Vehicle 4. 

The horizontal axis is the time in hours (72 hours for the 3-day test), and the vertical scale is the 

HC mass in the SHED for the test period. The high temperature diurnal (85°-120°-85°F) gave 

about twice the diurnal permeation rate on Vehicle 4, the 1999 Dodge Caravan. The 

continuous measurement of the tank venting emissions on the trap canister outside the SHED 

reported zero change for the test period. 

Figure 12 – 3 Day Diurnal Permeation 

Cumulative Permeation

Vehicle 4

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

The decrease in SHED mass 

shown here is discussed later 

in the Appendix. 
 

17

Another example of the permeation data, again from Vehicle 4, is offered in Figure 13. This 

chart shows both the diurnal temperature and the RVP effect. The lower pair of traces (green 

and blue) offers a comparison of the RVP effect at the lower diurnal temperature test 

conditions. The upper pair (red and black) compares the volatility effect at the higher test 

temperature. At both temperatures, the tests with the higher volatility fuel indicated higher 

permeation levels. 

Comparison plots for the diurnal results for the pilot study are summarized in Figures 14-17, 

arranged by emission control system technology. 

Figure 13 – Temperature and RVP Effects 

Cumulative Permeation

Vehicle 4

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

Low Temp - 9 Psi

High Temp - 9 Psi
 

18 

Diurnal Permeation Rates by Technology Group

Low Temp. 7.0 psi : E77 Project Vehicles 

746.8

546.7

325.4

262.0

503.7

375.6

133.1

105.0

0

100

200

300

400

500

600

700

800

3 9 10 1 2 4 6 7 8 5

Diurnal Permeation - mg/day

Pre-Enhanced Enhanced Near

Zero

20704

Vehicle 06 with

Implanted Leak

Figure 14 – Low Temperature Diurnal 7 psi Fuel 

Diurnal Permeation Rates by Technology Group

Hi Temp. 7.0 psi : E77 Project Vehicles 

1918.3

953.5

1689.3

530.3 471.5

1070.9

372.0

235.4 196.9

0

500

1000

1500

2000

3 9 10 1 2 4 6 7 8 5

Diurnal Permeation - mg/day

Pre-Enhanced Enhanced Near

Zero

27384

Vehicle 06 with

Implanted Leak

Figure 15 – High Temperature Diurnal 7 psi Fuel 
 

19

Diurnal Permeation Rates by Technology Group

Low Temp. 9.0 psi : E77 Project Vehicles 

571.1

214.4

695.9

468.5

150.4

0

100

200

300

400

500

600

700

800

12468

Diurnal Permeation - mg/day

Enhanced

Figure 16 – Low Temperature Diurnal 9 psi Fuel 

Diurnal Permeation Rates by Technology Group

Hi Temp. 9.0 psi : E77 Project Vehicles 

1048.8

387.4

1396.4

685.4

254.6

0

200

400

600

800

1000

1200

1400

1600

12468

Diurnal Permeation - mg/day

Enhanced

Figure 17 – High Temperature Diurnal 9 psi Fuel 
 

20 

An example of the canister breakthrough performance on Vehicle 4 is shown in Figure 18. 

These data are from the 3-day test at the lower diurnal temperatures with the 9 psi RVP fuel. 

The horizontal axis of the plot is the test time in hours for the 3 days. The left vertical axis 

shows the temperatures scale in degrees F. The green trace represents the VT-SHED ambient 

temperature as it is varied from 65° to 105°F, and the red trace is the fuel temperature as 

measured with the fuel tank skin thermocouple during the test. The blue trace is the change in 

the weight of the trap canister (shown on the right vertical scale in grams) used to capture the 

vehicle’s canister vent loss. 

No canister breakthrough was measured on the first day. On the second day at about the peak 

ambient temperature, the scale indicated about a gram of breakthrough. On the third day, more 

canister breakthrough was indicated, as the trap canister weight rose to a maximum of 17 

grams. 

The decrease in the trap canister weight that occurred during the last few hours of the test was 

the result of the “back-purging” of the system as the fuel tank temperature decreased. During 

this cooling period, the equilibrium partial pressure of the HC in the tank vapor space 

decreased, and air was drawn back into the tank to maintain the system pressure. This flow of 

air back into the vehicle’s fuel system purged the trap canister. 

 Figure 18 – Canister Breakthrough 

Canister Breakthrough and Temperature

Vehicle 4 - 9.0 PSI

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 10 20 30 40 50 60 70

Test Time - hrs

Temperature - deg F

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6926
 

21

Table 3 

Diurnal Vapor Generation (grams) for a 19 gallon tank at 40% fill 

 Fuel Tank Temperature Change 

 65°-103°F 85°-118°F

 7 psi Fuel 29.5 55.7 

 9 psi Fuel 56.2 125.0 

The GM Reddy model was used to estimate the vapor generation for a 19 gallon tank for the 

four diurnal test combinations that were included in the pilot study. These results are shown in 

Table 3. These calculations indicate that the vapor generation roughly doubles for both the 

increase in test temperature and the increase from 7 to 9 psi in fuel volatility. The high 

temperature and the higher volatility fuels create a fourfold increase in vapor generation. 

Another example of the canister breakthrough measurement is shown in Figure 19, from a test 

on Vehicle 1. The combination of high RVP and high temperature produced the first evidence 

of canister breakthrough, as shown with the green trace in the plot above. More interestingly, 

this plot shows that the permeation rate (red trace) increased significantly as the vehicle’s 

canister started to break-through into the external trap canister. This pointed out that the 

connection for the canister loss plumbing has to be made at the canister, rather than at the 

external vent solenoid. This is explained further in the following section. 

Cert Target 

Figure 19 - Canister Breakthrough 

Canister Breakthrough and Temperature

Vehicle 1 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25

Test Time - hrs

Temperature - deg F

-5 

5 

15 

25 

35 

45 

55 

65 

75 

85 

95 

Incremental Permeation - mg/2

Canister Breakthrough - grams

SHED Ambient

Incr. Permeation

Breakthrough

Test 6893

Peak Canister Breakthrough

was 70.5 gms at 13 hrs.
 

22 

The Original Hose Configurations on the Test Vehicles 

1. The fuel feed hose from the tank to the engine - contains liquid fuel 

2. The vapor hose from the tank to the canister - contains fuel vapor – during diurnal 

heating conditions, it carries head space vapor from the tank to the canister - during 

diurnal cooling conditions, it has purge vapors from the carbon bed at something 

less than the head space vapor concentration. 

3. The purge hose from the canister to the engine – during engine operation and at the 

start of the purge, it may have high concentration HC vapors, but for a majority of 

the purge, it contains mainly air, with low level HC concentration. 

4. The vent hose from the carbon canister to the vent solenoid/fresh air inlet filter for 

the canister. On rare occasions when the canister is overloaded and breaking 

through, it contains high level HC vapors. Otherwise, it contains only air. This 

hose is not required to be a low permeation material, and may be simply NBR. 

5. The laboratory’s affixed connection hose to route the canister breakthrough vapors 

to the SHED external trap canister for collection and quantification. 

The hose that was to be circumvented is the vent hose identified as #4 in Figure 20. Another 

illustration is shown in Figure 21. 

1 

2

3

4

5 

Figure 20– Hose Configurations 
 

23

 

Procedures were revised to make the test connection directly at the canister, rather than at the 

original site, the remote vent. The Teflon® hose material used to route the canister vent loss to 

the outside of the SHED (identified as # 5 in a previous figure) was verified to be low 

permeation material. A discussion of this investigation is offered in the Appendix. 

THE ISSUE OF NON-FUEL EMISSIONS 

One major goal of this pilot study was to quantify the fuel emissions from vehicles under the 

chosen test conditions. Non-fuel (background) emissions8

 are known to be present in the 

ambient samples measured. These background emissions were to be minimized or identified in 

this study. Vehicle selection eliminated candidates with recent paint repairs or newly replaced 

tires, or any vehicles with identifiable HC odors or spills detectable with a sniffer in the trunk 

or interior. The remaining paint and vinyl contributions are confounded into the vehicle level 

measurements. 

Other non-fuel emissions can originate from washer solvent (methanol) and refrigerant (R-12, 

R-134a). The laboratory purchased and experimented with an INNOVA9

 analyzer to identify 

methanol and refrigerants present in the measurements on a routine basis towards the end of the 

pilot program. 

 

8

 See SAE 912373, “Real-Time Non-Fuel Background Emissions,” H. Haskew, et al. 9

 Model 1412 Photoacoustic Multigas Analyzer from California Analytical Instruments, Inc. 

Hose 4 – 

Possibly a high 

permeation 

material 

Figure 21 – Canister Vent Hose – Vehicle Installation 
 

24 

 

The discussion that follows concerns the issues with Vehicle 8, and how they were resolved 

once the anomaly was identified as a large refrigerant leak. The diurnal permeation plot for 

Vehicle 8 (Figure 22) showed an atypical increase in the permeation during the last four hours 

of the test. The INNOVA allowed continual measurement of methanol and refrigerant (R134a) 

in the SHED during the diurnal test. Subtracting those contaminants from the HC (FID) reading 

provided insight into the source of the unusual data. 

The Explorer (Vehicle 8) had a refrigerant leak that was identified by the FID as a 

hydrocarbon, and thought to be gasoline. When the FID reading was corrected, the diurnal 

mass was reduced from 280 mg/ day to 109, a 61% reduction. The methanol correction was 

insignificant. The R134a measurement, shown in the red trace in Figure 23, is calculated as if it 

were a fuel molecule, using the customary density of fuel vapors (16.83 grams per cubic foot 

per ppm carbon). The actual mass of refrigerant is much higher, due to the additional noncarbon and hydrogen atoms contained in the molecule. 

The methanol measured was very low in this test, and the ethanol identified by the INNOVA 

was ~ 20 mg, a trace hang-over measurement. The ethanol is included in the corrected SHED 

mass, since it is fuel. 

Effect of Non-Fuel Contaminants

Vehicle 8 - 7.0 PSI

0

50

100

150

200

250

300

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6954

 Figure 22 – Non-Fuel Emissions 

Non-Fuel Component Cumulative Permeation

Vehicle 8 - 7 psi

-20

0

20

40

60

80

100

120

140

160

180

200

0 5 10 15 20 25

Test Time - hrs.

Cumulative Permeation - mg

R134a

Methanol

Ethanol

Low Temperature Diurnal

 Figure 23 – Non-Fuel Component Permeation 
 

25

Figure 24 shows the effect of the non-fuel components on the total high temperature diurnal 

permeation on Vehicle 8. 

The low temperature 7 psi diurnal test on the Cavalier Vehicle 6 had both refrigerant and 

methanol present at significant levels. Figure 25 shows the test results with the red trace 

indicating the “normal” FID measurement, and the two corrections performed in a step-wise 

method, first subtracting the R134a misidentified as gasoline (blue trace), and then subtracting 

the methanol to obtain the final corrected diurnal result as shown in the black trace. The 

diurnal measurement is corrected from 477 to 376 mg day, a 21% reduction. 

Effect of Non-Fuel Contaminants

Vehicle 8 - 7.0 PSI

0

50

100

150

200

250

300

350

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6956

Effect of Non-Fuel Contaminants

Vehicle 6 - 7.0 PSI

0

100

200

300

400

500

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6953

Figure 25 – Non-Fuel Effects - Low Temperature Diurnal 
 

26 

The R134a and methanol measurements for this test (6953) are shown in Figure 26 on the 

following page. 

Figure 26 - Non-Fuel Component Permeation 

Non-Fuel Contaminant Cumulative Permeation

Vehicle 6 - 7.0 PSI

0

10

20

30

40

50

60

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

Low Temp Diurnal

Test 6953
 

27

AN OVERVIEW OF WHAT WAS LEARNED 

The Pilot Study accomplished the objectives of the project and added to the bank of knowledge 

that helps in understanding the mechanisms and magnitude of vehicle evaporative emissions. 

These are summarized as: 

• Tank Venting (Canister Losses) can be separated from the permeation. See the 

plot at Figure 18, “Canister Breakthrough” that illustrates the tank venting, or 

canister breakthrough, occurring during heating periods on the third day, and then 

decreasing during the “back-purge” period. 

• Permeation rates increase with temperature. See the many plots of permeation 

rate versus time (“Diurnal Time Response”) in Appendix II organized by vehicle 

number. 

• Permeation emissions are higher when measured with 9 psi RVP E0 gasoline 

than with 7 psi E0 gasoline. See figure 13 at page 18. Permeation is not thought 

to be a function of system pressure, but we found it to increase with higher vapor 

pressure fuel. The explanation is that the higher vapor pressure creates higher vapor 

concentrations in the fuel vapor components (head space, fuel cap seal, vapor 

handling lines). 

• Canister venting connection must be made at the canister. Review the text 

starting at page 22, and Figures 19, 20 and 21. 

• High volatility and temperature can create excessive fuel vapors that exceed 

canister capacity. See examples of the high temperature tests on 9 psi fuel in 

Figures 18 and 19. 

• Refrigerant and methanol (non-fuel components) can be a significant fraction 

of the SHED measurement. See “The Issue of Non-Fuel Emissions” starting at 

page 25 of this report. 
 

28 

ACKNOWLEDGEMENTS: 

The authors want to thank and acknowledge the staff and steering committee that guided this 

program: 

David L. Lax API 

Ben Hancock CARB 

Jeff Long CARB 

Hector Maldonado CARB 

Mike Ingham Chevron 

Jenny Spravsow Chrysler 

Ken J. Wright ConocoPhillips 

Brent Bailey CRC 

Jane Beck CRC 

Chris Tennant CRC 

David Brzezinski EPA 

Connie Hart EPA 

Dominic DiCicco Ford 

Cynthia Williams Ford 

Steve Cadle GM 

Jeff Jetter Honda 

Mani Natarajan Marathon 

David N. Patterson Mitsubishi 

King D. Eng Shell 

Hannah Murray Toyota 
 

29

Appendix I 

Additional Information 

The following discussion is intended to show that the permeation of the test vent hoses used by 

ATL are, for these purposes, zero. The basic contamination level inherent in a SHED is 

discussed first, followed by a presentation of test data intended to measure the permeation of 

the test vent hose. The trap canister HC collection is also compared to the value predicted by 

the Reddy model. 

Discussion: Any variable temperature 

SHED has an inherent contamination 

level which can be as high as 50 mg per 

day under the regulations for an 

enhanced evap certification test. The 

contamination is thought to be leftover 

HC from previous experiences that have 

condensed on the SHED internal surfaces 

during the cooling period. One can 

measure the contamination level by 

performing a diurnal test with nothing in 

the SHED, i.e., a “blank SHED.” 

Figure 27 shows a recent (9/15/06) 

“blank SHED” test result in ATL’s 

SHED 15, one of the two that are used 

for the CRC Projects E-77 and E-65 

evaluations. An almost identical value was measured in SHED 14 during the same period. The 

HC mass in a blank SHED increases as the SHED is heated, and then decreases slightly during 

cooling. The mass in the SHED was estimated to be as high as ~13 mg at the peak value, 

decreasing to ~7 mg at the test end. The contamination level can be minimized by repeated 

heating and purging of the SHED, washing the internal surfaces with a non-HC soap, and 

avoiding tests of vehicles or objects with high emission levels. A 5 to 10 mg level is a realistic 

goal for day-to-day performance. 

Vent Hose Evaluation - The laboratory located a 3 gallon steel tank, previously used to hold 

calibration gases. The single inlet fitting was replaced with a stainless fitting that mated to the 

3/8” ID Teflon® vent hose that was used in the SHED to vent the fuel system to the outside of 

the enclosure. The vent hose is approximately 6’ long and terminates at either end with a 

Swagelok compression fitting. The test set-up is shown in Figure 28. The intent is for the only 

item that can permeate in the SHED to be the vent hose. The 3 gallon container was filled with 

1.5 gallons (50%) of the E77 7 psi test fuel. The trap canister outside the SHED was used to 

collect any HC vapors that were emitted from the tank. Several diurnal tests were performed in 

SHEDs 14 and 15 with this test configuration. 

SHED 15 Blank Test 

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 5 10 15 20 25 30

Time in Hours

SHED Mass in mg

Figure 27 – Blank SHED Test 
 

30 

The test results for the vent hose in SHED 14 were lower than the blank SHED results (Figure 

29), i.e., no permeation from the hose. Similar results were obtained in SHED 15, as shown in 

Figure 30. 

SHED HC vs Test Time

0

5

10

15

20

25

0 6 12 18 24

Test Time - hours

SHED HC - mg

Blank

Tank

SHED 14

Steel cylinder 50% filled 

with 7 psi test gasoline 

Teflon® vent hose 

Figure 29 – Blank SHED Test Results – SHED 14 

Figure 28 – Blank SHED Test Set-up 
 

31

The two day test results in SHED 15 are shown in the blue traces in Figure 30, as if they were 

both run as single day results. The blank SHED results are shown in the red trace. Again, the 

conclusion is the same: there is no significant permeation from the Teflon® vent hose used in 

the test program for E-65 and E-77. 

The trap canister collected the venting emissions from the steel cylinder. The results were 

repeated very closely from day-to-day, as shown in Figure 31. The measured emissions were 

~3.4 grams during the heating cycle from the 1.5 gallon of vapor space. The back purge of the 

trap canister as the fuel tank cools is apparent. The Reddy model predicts 3.205 grams for a 67 

to 103°F temperature heating excursion, which compares favorably with the measured values. 

Figure 30 – Blank SHED Test Results – SHED 15 

Collector Weight Change vs Test Time

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 4 8 12 16 20 24

Test Time - hours

Collector Weight Change - gms

Collector - Day 1

Collector - Day 2

SHED 15

Figure 31 – Trap Canister Emissions – Blank SHED Test 

SHED HC vs Test Time

0

5

10

15

20

25

0 4 8 12 16 20 24

Test Time - hours

SHED HC - mg

Blank

Tank - Day 1

Tank - Day 2

SHED 15
 

32 

Comment: 

The Teflon® vent hose does not materially contribute to the evaluation, and it appears that the 

trap canister works. 

Mass “Loss” during the Diurnal Cooling Period 

Plots of diurnal mass results sometimes indicate an apparent mass “loss” during the cooling 

period. Figure 12 is repeated below to illustrate this result, most apparent in the third day’s test 

results with the high temperature test conditions (red trace). The vertical scale is the calculated 

mass in the SHED. That the mass is shown to decrease suggests a “leak” or other problem in 

the test results. 

This condition has been observed in many test programs, and usually is more evident when the 

HC concentration in the SHED is high. We believe that this is a result of partial adsorption, or 

condensation, of the HC vapors on the cool surfaces in the heat exchanger as it tries to drive the 

SHED ambient temperature down during the cooling cycle. 

Cumulative Permeation

Vehicle 4

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

 Figure 32 - Repeat of Figure 12-Three Day Diurnal Permeation 
 

33

Appendix II 

Test Data Plots 

All Vehicles
 

34 

Static 86 F Permeation

Vehicle 1 - 7 PSI

240

242

244

246

248

250

252

254

256

258

260

262

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 8.6 mg/hr (206 mg/day)

Incremental Incr. w/ pressurized tank 3.0 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6875

1996 Chevrolet S-10 Enhanced SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

01 7.0 Static Perm 07/06/06 6875 8.6

Press. Incr. 3.0

Prs+Fuel Incr. 0.0

mg

7.0 Dynamic RL 07/07/06 25632 331.4

HS 65.0

RL + HS 396.4

7.0 DHB 65-105 06/23/06 6857 325.4 0.0

7.0 DHB 85-120 06/28/06 6865 530.3 0.0

9.0 DHB 65-105 07/18/06 6888 572.1 0.0

9.0 DHB 85-120 07/20/06 6893 1048.8 70.5

Vehicle 1 
 

35

Running Loss and Hot Soak

Vehicle 1 - 7.0 Psi

y = 0.1381x2 - 0.3967x

R2

 = 0.9216

y = -0.0312x2

 + 4.728x + 236.07

R2

 = 0.1685

0

100

200

300

400

500

600

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25632

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.017 g/mi

Diurnal Time Response

Vehicle 1 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-5

0

5

10

15

20

25

30

35

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6857
 

36 

Dynamic Diurnal

Vehicle 1 - 7.0 Psi

-5

0

5

10

15

20

25

30

35

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6857

Diurnal Time Response

Vehicle 1 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

0

10

20

30

40

50

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6865
 

37

Dynamic Diurnal

Vehicle 1 - 7.0 Psi

0

10

20

30

40

50

60

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6865

Diurnal Time Response

Vehicle 1 - 9.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

0

10

20

30

40

50

60

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6888
 

38 

Dynamic Diurnal

Vehicle 1 - 9.0 Psi

0

10

20

30

40

50

60

70

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6888

Diurnal Time Response

Vehicle 1 - 9.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-5

15

35

55

75

95

115

135

155

175

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 
 

39

Dynamic Diurnal

Vehicle 1 - 9.0 Psi

-20

0

20

40

60

80

100

120

140

160

180

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6893

Canister Breakthrough and Temperature

Vehicle 1 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25

Test Time - hrs

Temperature - deg F

-5 

5 

15 

25 

35 

45 

55 

65 

75 

85 

95 

Incremental Permeation - mg/2

Canister Breakthrough - grams

SHED Ambient

Incr. Permeation

Breakthrough

Test 6893

Peak Canister Breakthrough

was 70.5 gms at 13 hrs.
 

40 

Cumulative Permeation

Vehicle 1

0

200

400

600

800

1000

1200

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

 Low Temp - 7 Psi

 High Temp - 7 Psi

 Low Temp - 9 Psi

 High Temp - 9 Psi
 

41

2000 Toyota Tacoma Enhanced SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

2 7.0 Static Perm 07/19/06 6890 19.1

Press. Incr. 0.0

Prs+Fuel Incr. 0.0

7.0 Dynamic RL 07/19/06 25634 520.2

HS 0.0

RL + HS 520.2

7.0 DHB 65-105 07/13/06 6883 407.2 0.0

7.0 DHB 65-105 08/01/06 6904 262.0 0.0

7.0 DHB 85-120 07/21/06 6896 471.5 0.0

9.0 DHB 65-105 07/25/06 6899 214.4 0.0

9.0 DHB 85-120 09/12/06 6929 387.4 6.3

Static 86 F Permeation

Vehicle 2 - 7 PSI

200

205

210

215

220

225

230

235

240

245

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 19.1 mg/hr (429 mg/day)

Incremental Incr. w/ pressurized tank 0.0 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6890

Vehicle 2 
 

42 

Running Loss and Hot Soak

Vehicle 2 - 7.0 Psi

y = -0.1134x2 + 14.857x

R2

 = 0.8793

y = 0.0189x2

 - 3.6763x + 592.22

R2

 = 0.5375

0

100

200

300

400

500

600

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25634

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.025 g/mi

Diurnal Time Response

Vehicle 2 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

0

10

20

30

40

50

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6883
 

43

Dynamic Diurnal

Vehicle 2 - 7.0 Psi

-10

0

10

20

30

40

50

60

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6883

Diurnal Time Response

Vehicle 2 - 7.0 Psi (Repeat)

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-15

-10

-5

0

5

10

15

20

25

30

35

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6904
 

44 

Diurnal Time Response

Vehicle 2 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

0

10

20

30

40

50

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6896

Dynamic Diurnal

Vehicle 2 - 7.0 Psi (Repeat)

-20

-10

0

10

20

30

40

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6904
 

45

Dynamic Diurnal

Vehicle 2 - 7.0 Psi

-10

0

10

20

30

40

50

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6896

Diurnal Time Response

Vehicle 2 - 9.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

-5

0

5

10

15

20

25

30

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6899
 

46 

Dynamic Diurnal

Vehicle 2 - 9.0 Psi

-10

-5

0

5

10

15

20

25

30

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6899

Diurnal Time Response

Vehicle 2 - 9.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

0

5

10

15

20

25

30

35

40

45

50

 Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6929
 

47

Dynamic Diurnal

Vehicle 2 - 9.0 Psi

0

5

10

15

20

25

30

35

40

45

50

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6929

Canister Breakthrough and Temperature

Vehicle 2 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25

Test Time - hrs

Temperature - deg F

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6929
 

48 

Cumulative Permeation

Vehicle 2

0

100

200

300

400

500

600

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

Low Temp - 7 Psi (Repeat)

High Temp - 7 Psi

Low Temp - 9 Psi

High Temp - 9 Psi
 

49

1992 Honda Accord Pre-enhanced SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

3 7.0 Static Perm 07/28/06 6902 32.3

Press. Incr. 2.6

Prs+Fuel Incr. 0.0

7.0 Dynamic RL 08/01/06 25635 753.3

HS 13.8

RL + HS 767.0

7.0 72 DHB 65-105 08/11/06 6915 Day 1 746.8 0.1

 Day 2 782.5 0.4

Day 3 1304.4 2.4

7.0 72 DHB 85-120 09/01/06 6925 Day 1 1918.3 1.7

Day 2 3760.8 18.7

Day 3 5674.1 20.4

Static 86 F Permeation

Vehicle 3 - 7 PSI

280

290

300

310

320

330

340

350

360

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 32.3 mg/hr (775 mg/day)

Incremental Incr. w/ pressurized tank 2.6 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank Power the

Fuel Pump 

Test 6902

Vehicle 3 
 

50 

Running Loss and Hot Soak

Vehicle 3 - 7.0 Psi

y = -0.0093x2 + 16.242x

R2

 = 0.9985

y = -0.0095x2

 + 1.8287x + 679.63

R2

 = 0.7731

0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25635

Running Loss

Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.039 g/mi

Diurnal Time Response

Vehicle 3 - 7.0 Psi : Repeat

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 10 20 30 40 50 60 70

Test Time - hours

SHED AMbient Temperature - deg F

-50

0

50

100

150

200

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6915
 

51

Dynamic Diurnal

Vehicle 3 - 7.0 Psi : Repeat

-40

10

60

110

160

210

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6915

Diurnal Time Response

Vehicle 3 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 10 20 30 40 50 60 70

Test Time - hours

SHED AMbient Temperature - deg F

-250

250

750

1250

1750

2250

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6925
 

52 

Dynamic Diurnal

Vehicle 3 - 7.0 Psi

-500

0

500

1000

1500

2000

2500

80 90 100 110 120 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6925

Canister Breakthrough and Temperature

Vehicle 3 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 10 20 30 40 50 60 70

Test Time - hrs

Temperature - deg F

-250 

250 

750 

1250 

1750 

2250 

Incremental Permeation - mg

Canister Breakthrough - 45 x grams

SHED Ambient

Incr. Permeation

Breakthrough

Test 6925

Peak Canister

Breakthrough

was 46 gms @

 11 hrs of day 3
 

53

Cumulative Permeation

Vehicle 3

0

2000

4000

6000

8000

10000

12000

14000

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp 7 Psi

High Temp 7 Psi
 

54 

1999 Dodge Caravan Enhanced SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

4 7.0 Static Perm 08/09/06 6912 50.3

Press. Incr. 0.0

Prs+Fuel Incr. 0.0

7.0 Dynamic RL 08/10/06 25636 184.6

HS 73.5

RL + HS 258.1

7.0 72 DHB 65-105 08/22/06 6919 Day 1 503.7 0.00

 Day 2 454.0 0.00

Day 3 606.3 0.00

7.0 72 DHB 85-120 08/29/06 6922 Day 1 1070.9 0.00

 Day 2 886.5 0.48

Day 3 1804.1 0.31

9.0 72 DHB 65-105 09/03/06 6926 Day 1 695.9 0.00

 Day 2 556.7 1.19

Day 3 665.0 12.85

9.0 72 DHB 85-120 09/07/06 6927 Day 1 1396.4 23.79

 Day 2 1175.1 71.43

Day 3 1114.9 80.49

Static 86 F Permeation

Vehicle 4 - 7 PSI

300

320

340

360

380

400

420

440

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 50.3 mg/hr (1207 mg/day)

Incremental Incr. w/ pressurized tank 0.0 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6912

Vehicle 4 
 

55

Running Loss and Hot Soak

Vehicle 4 - 7.0 Psi

y = -0.0398x2 + 5.5741x

R2

 = 0.9865

y = -0.0087x2

 + 2.3904x + 104.51

R2

 = 0.9004

0

50

100

150

200

250

300

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25636

Running Loss

Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.009 g/mi

Diurnal Time Response

Vehicle 4 - 7.0 Psi : Repeat

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-20

-10

0

10

20

30

40

50

60

70

80

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6919
 

56 

Dynamic Diurnal

Vehicle 4 - 7.0 Psi : Repeat

-20

-10

0

10

20

30

40

50

60

70

80

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6919

Diurnal Time Response

Vehicle 4 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-10

10

30

50

70

90

110

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6922
 

57

Dynamic Diurnal

Vehicle 4 - 7.0 Psi

-20

0

20

40

60

80

100

120

80 90 100 110 120 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6922

Canister Breakthrough and Temperature

Vehicle 4 - 7.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 10 20 30 40 50 60 70

Test Time - hrs

Temperature - deg F

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6922
 

58 

Diurnal Time Response

Vehicle 4 - 9.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-10

0

10

20

30

40

50

60

70

80

90

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6926

Dynamic Diurnal

Vehicle 4 - 9.0 Psi

-20

0

20

40

60

80

100

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6926
 

59

Canister Breakthrough and Temperature

Vehicle 4 - 9.0 PSI

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 10 20 30 40 50 60 70

Test Time - hrs

Temperature - deg F

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6926

Diurnal Time Response

Vehicle 4 - 9.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-25

-5

15

35

55

75

95

115

135

155

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6927
 

60 

Dynamic Diurnal

Vehicle 4 - 9.0 Psi

-20

0

20

40

60

80

100

120

140

160

80 90 100 110 120 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6927

Canister Breakthrough and Temperature

Vehicle 4 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 10 20 30 40 50 60 70

Test Time - hrs

Temperature - deg F

0 

50 

100 

150 

200 

250 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6927
 

61

Cumulative Permeation

Vehicle 4

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

Low Temp - 9 Psi

High Temp - 9 Psi

Cumulative Permeation

Vehicle 4

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi
 

62 

2007 Ford Taurus LEV II SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

5 7.0 Static Perm 08/30/06 6923 9.2

Press. Incr. 0.8

Prs+Fuel Incr. 6.8

7.0 Dynamic RL 09/07/06 25638 35.8

HS 0.5

RL + HS 36.3

7.0 72 DHB 65-105 09/09/06 6928 Day 1 108.4 0.00

 Day 2 52.7 0.00

Day 3 92.9 0.00

7.0 72 DHB 65-105 09/15/06 6931 Day 1 101.5 0.00

 Day 2 55.4 0.00

Day 3 95.4 0.00

7.0 72 DHB 85-120 09/19/06 6933 Day 1 196.9 0.00

 Day 2 146.2 0.00

Day 3 134.2 0.00

Static 86 F Permeation

Vehicle 5 - 7 PSI

255

260

265

270

275

280

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 9.2 mg/hr (221 mg/day)

Incremental Incr. w/ pressurized tank 0.8 mg/hr (19 mg/day)

Incremental Incr. w/ Fuel Pump 'On' 6.0 mg/hr (144 mg/day)

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6923

Vehicle 5 
 

63

Running Loss and Hot Soak

Vehicle 5 - 7.0 Psi

y = -0.0145x2 + 1.3049x

R2

 = 0.7662

y = 0.0003x2

 - 0.0278x + 34.63

R2

 = 0.0062

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25638

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.002 g/mi

Diurnal Time Response

Vehicle 5 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-15

-10

-5

0

5

10

15

20

25

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6928
 

64 

Dynamic Diurnal

Vehicle 5 - 9.0 Psi

-20

-15

-10

-5

0

5

10

15

20

25

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6928

Diurnal Time Response

Vehicle 5 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-10

-5

0

5

10

15

20

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6931
 

65

Dynamic Diurnal

Vehicle 5 - 9.0 Psi

-10

-5

0

5

10

15

20

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6931

Diurnal Time Response

Vehicle 5 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Test Time - hours

SHED AMbient Temperature - deg F

-15

-10

-5

0

5

10

15

20

25

30

Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6933
 

66 

Dynamic Diurnal

Vehicle 5 - 9.0 Psi

-10

-5

0

5

10

15

20

25

30

80 90 100 110 120 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Day 1

Day 2

Day 3

Test 6933

Cumulative Permeation

Vehicle 5

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

Low Temp - 7Psi Repeat

High Temp - 7 Psi
 

67

1996 Chevrolet Cavalier SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

6 7.0 Static Perm 09/27/06 6939 25.8

Press. Incr. 0.0

Prs+Fuel Incr. 15.8

7.0 Dynamic RL 09/27/06 25640 214.6

HS 56.1

RL + HS 270.8

7.0 24 DHB 65-105 10/19/06 6953 Day 1 477.3 375.6 0.00

7.0 24 DHB 85-120 10/24/06 6955 Day 1 468.2 372.0 0.00

9.0 24 DHB 65-105 11/02/06 6959 Day 1 569.2 468.5 0.00

9.0 24 DHB 85-120 11/08/06 6961 Day 1 785.1 685.4 18.92

Static 86 F Permeation

Vehicle 6 - 7 PSI

175

185

195

205

215

225

235

245

255

265

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 25.8 mg/hr (619 mg/day)

Incremental Incr. w/ pressurized tank 0.0 mg/hr 

Incremental Incr. w/ Fuel Pump 'On' 15.8 mg/hr (379 mg/day)

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6939

Vehicle 6 
 

68 

Running Loss and Hot Soak

Vehicle 6 - 7.0 Psi

y = -0.0127x2 + 5.0669x

R2

 = 0.9945

y = -0.0031x2

 + 1.1342x + 183.94

R2

 = 0.8374

0

50

100

150

200

250

300

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25640

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.011 g/mi

Diurnal Time Response

Vehicle 6 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-20

-10

0

10

20

30

40

50

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6953

Low Temp Diurnal
 

69

Dynamic Diurnal

Vehicle 6 - 7.0 Psi

-5

0

5

10

15

20

25

30

35

40

45

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6953

Low Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 6 - 7.0 PSI

0

10

20

30

40

50

60

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

Low Temp Diurnal

Test 6953
 

70 

Effect of Non-Fuel Contaminants

Vehicle 6 - 7.0 PSI

0

100

200

300

400

500

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6953

Diurnal Time Response

Vehicle 6 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-5

0

5

10

15

20

25

30

35

40

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6955

High Temp Diurnal
 

71

Dynamic Diurnal

Vehicle 6 - 7.0 Psi

-5

0

5

10

15

20

25

30

35

40

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6955

High Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 6 - 7.0 PSI

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

High Temp Diurnal

Test 6955
 

72 

Effect of Non-Fuel Contaminants

Vehicle 6 - 7.0 PSI

0

100

200

300

400

500

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6955

Diurnal Time Response

Vehicle 6 - 9.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-20

-10

0

10

20

30

40

50

60

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6959

Low Temp Diurnal
 

73

Dynamic Diurnal

Vehicle 6 - 9.0 Psi

-5

5

15

25

35

45

55

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6959

Low Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 6 - 9.0 PSI

-10

0

10

20

30

40

50

60

70

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

Low Temp Diurnal

Test 6959
 

74 

Effect of Non-Fuel Contaminants

Vehicle 6 - 9.0 PSI

0

100

200

300

400

500

600

700

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6959

Diurnal Time Response

Vehicle 6 - 9.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

0

10

20

30

40

50

60

70

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6961

High Temp Diurnal
 

75

Dynamic Diurnal

Vehicle 6 - 9.0 Psi

-10

0

10

20

30

40

50

60

70

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6961

High Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 6 - 9.0 PSI

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

High Temp Diurnal

Test 6961
 

76 

Effect of Non-Fuel Contaminants

Vehicle 6 - 9.0 PSI

0

100

200

300

400

500

600

700

800

900

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6961

Canister Breakthrough and Temperature

Vehicle 6 - 9.0 PSI

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25

Test Time - hrs

Temperature - deg F

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

Canister Breakthrough - grams

SHED Ambient

Fuel Temp

Breakthrough

Test 6961
 

77

Cumulative Permeation - Corrected Mass

Vehicle 6

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

Low Temp - 9 Psi

High Temp - 9 Psi
 

78 

1996 Chevrolet Cavalier Enhanced (with implanted leak) SHED SHED

Results Results Canister

mg/hr mg/hr mg/day mg/day Loss

Veh Fuel Test Type Date Test# (Raw) (Corrected) (Raw) (Corrected) g

7 7.0 Static Cap (.020") 11/14/06 6963 59.0

Fuel Incr. 2358.3

 7.0 Dynamic RL 11/17/06 25642 258.7 227.6

HS 149.3 129.0

RL + HS 408.1 356.6

7.0 24 DHB 65-105 11/21/06 6964 Day 1 21036 20704 0

7.0 24 DHB 85-120 11/30/06 6966 Day 1 27824 27384 0

Permeation

Static 86 F Permeation

Vehicle 7 (with implanted leak) - 7 PSI

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 59.0 mg/hr (1416 mg/day)

Incremental Incr. w/ Fuel Pump 'On' 2417.3 mg/hr

Steady State

Permeation

Power the

Fuel Pump 

Vehicle 6 Test 6963

Vehicle 7 
 

79

Running Loss and Hot Soak

Vehicle 7 (with implanted leak) - 7.0 Psi

y = -0.0525x2 + 6.756x

R2

 = 0.943

y = -0.0453x2

 + 8.8502x - 88.065

R2

 = 0.929

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Corrected Permeation - mg

Test 25642

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = .012 g/mi

Diurnal Time Response

Vehicle 7 (with implanted leak) - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-500

0

500

1000

1500

2000

2500

3000

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6964

Low Temp Diurnal
 

80 

Dynamic Diurnal

Vehicle 7 (with implanted leak) - 7.0 Psi

-500

0

500

1000

1500

2000

2500

3000

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6964

Low Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 7 (with implanted leak) - 7.0 PSI

0

50

100

150

200

250

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation + Leak - mg

R134a

Methanol

Low Temp Diurnal

Test 6964
 

81

Effect of Non-Fuel Contaminants

Vehicle 7 (with implanted leak) - 7.0 PSI

0

5000

10000

15000

20000

25000

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation + Leak - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6964

Diurnal Time Response

Vehicle 7 (with implanted leak) - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-1000

0

1000

2000

3000

4000

5000

6000

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6966

High Temp Diurnal
 

82 

Dynamic Diurnal

Vehicle 7 (with implanted leak) - 7.0 Psi

-1000

0

1000

2000

3000

4000

5000

6000

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Hourly Permeation - mg/hr

Test 6966

High Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 7 (with implanted leak) - 7.0 PSI

0

50

100

150

200

250

300

350

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

High Temp Diurnal

Test 6966
 

83

Effect of Non-Fuel Contaminants

Vehicle 7 (with implanted leak) - 7.0 PSI

0

5000

10000

15000

20000

25000

30000

35000

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6966

Cumulative Permeation - Corrected Mass

Vehicle 7 (with implanted leak)

0

5000

10000

15000

20000

25000

30000

35000

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation + Leak - mg.

Low Temp - 7 Psi

High Temp - 7 Psi
 

84 

1996 Ford Explorer SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

8 7.0 Static Perm 10/10/06 6949 6.8

Press. Incr. 2.3

Prs+Fuel Incr. 0.3

7.0 Dynamic RL 10/12/06 25641 171.3

HS 73.8

RL + HS 245.0

7.0 24 DHB 65-105 10/21/06 6954 Day 1 279.7 133.1 0.00

7.0 24 DHB 85-120 10/26/06 6956 Day 1 298.0 235.4 0.00

9.0 24 DHB 65-105 10/28/06 6957 Day 1 227.5 150.4 0.00

9.0 24 DHB 85-120 11/09/06 6962 Day 1 346.2 254.6 128.68

Static 86 F Permeation

Vehicle 8 - 7 PSI

210

212

214

216

218

220

222

224

226

228

230

0 20 40 60 80 100 120

Test Time - minutes

SHED Mass - mg

Basic Permeation Rate at 86 6.8 mg/hr (164 mg/day)

Incremental Incr. w/ pressurized tank 2.3 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.3 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6949

Vehicle 8 
 

85

Running Loss and Hot Soak

Vehicle 8 - 7.0 Psi

y = 0.0126x2 + 2.7798x

R2

 = 0.975

y = -0.0152x2

 + 3.1951x + 74.852

R2

 = 0.8487

0

50

100

150

200

250

300

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25641

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.009 g/mi

Diurnal Time Response

Vehicle 8 - 7.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-4

-2

0

2

4

6

8

10

12

14

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6954

Low Temp Diurnal
 

86 

Dynamic Diurnal

Vehicle 8 - 7.0 Psi

-4

-2

0

2

4

6

8

10

12

14

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6954

Low Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 8 - 7.0 PSI

-20

0

20

40

60

80

100

120

140

160

180

200

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

Low Temp Diurnal

Test 6954
 

87

Effect of Non-Fuel Contaminants

Vehicle 8 - 7.0 PSI

0

50

100

150

200

250

300

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6954

Non-Fuel Component Cumulative Permeation

Vehicle 8 - 7 psi

-20

0

20

40

60

80

100

120

140

160

180

200

0 5 10 15 20 25

Test Time - hrs.

Cumulative Permeation - mg

R134a

Methanol

Ethanol

Low Temperature Diurnal

Test 6954
 

88 

Diurnal Time Response

Vehicle 8 - 7.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

-5

0

5

10

15

20

25

30

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6956

High Temp Diurnal

Dynamic Diurnal

Vehicle 8 - 7.0 Psi

-10

-5

0

5

10

15

20

25

30

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6956

High Temp Diurnal
 

89

Non-Fuel Contaminant Cumulative Permeation

Vehicle 8 - 7.0 PSI

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

High Temp Diurnal

Test 6956

Effect of Non-Fuel Contaminants

Vehicle 8 - 7.0 PSI

0

50

100

150

200

250

300

350

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6956
 

90 

Diurnal Time Response

Vehicle 8 - 9.0 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

-5

0

5

10

15

20

25

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6957

Low Temp Diurnal

Dynamic Diurnal

Vehicle 8 - 9.0 Psi

-10

-5

0

5

10

15

20

25

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6957

Low Temp Diurnal
 

91

Non-Fuel Contaminant Cumulative Permeation

Vehicle 8 - 9.0 PSI

0

10

20

30

40

50

60

70

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

Low Temp Diurnal

Test 6957

Effect of Non-Fuel Contaminants

Vehicle 8 - 9.0 PSI

0

50

100

150

200

250

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6957
 

92 

Diurnal Time Response

Vehicle 8 - 9.0 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-5

0

5

10

15

20

25

30

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6962

High Temp Diurnal

Dynamic Diurnal

Vehicle 8 - 9.0 Psi

-10

-5

0

5

10

15

20

25

30

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6962

High Temp Diurnal
 

93

Non-Fuel Contaminant Cumulative Permeation

Vehicle 8 - 9.0 PSI

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

R134a

Methanol

High Temp Diurnal

Test 6957

Effect of Non-Fuel Contaminants

Vehicle 8 - 9.0 PSI

0

50

100

150

200

250

300

350

400

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6962
 

94 

Cumulative Permeation - Corrected Mass

Vehicle 8

0

50

100

150

200

250

300

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

High Temp - 7 Psi

Low Temp - 9 Psi

High Temp - 9 Psi

Temperature Effect

RVP Effect
 

95

1995 Plymouth Neon Pre-Enhanced SHED SHED

Results Results Canister

mg/hr mg/hr mg/day mg/day Loss

Veh Fuel Test Type Date Test# (Raw) (Corrected) (Raw) (Corrected) g

9 7.0 Static Perm 01/09/07 6975 37.8 27.3

Press. Incr. 0.0 0.0

Prs+Fuel Incr. 0.4 8.8

7.0 Dynamic RL 12/21/06 25646 209.3

HS 66.0

RL + HS 275.3

7.0 24 DHB 65-105 01/03/07 6973 Day 1 1633.6 546.7 0.13

7.0 24 DHB 85-120 01/06/07 6974 Day 1 1053.8 953.5 9.42

Permeation

Static 86 F Permeation

Vehicle 9 - 7 PSI

0

10

20

30

40

50

60

70

0 20 40 60 80 100 120

Test Time - minutes

Corrected SHED Mass - mg

Basic Permeation Rate at 86 27.3 mg/hr (907 mg/day)

Incremental Incr. w/ pressurized tank 0.0 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 8.8 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 

6975b

Vehicle 9 
 

96 

Running Loss and Hot Soak

Vehicle 9 - 7.0 Psi

y = -0.0522x2 + 6.7607x

R2

 = 0.9763

y = -0.0084x2

 + 2.3146x + 122.92

R2

 = 0.944

0

50

100

150

200

250

300

350

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25646

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.011 g/mi

Diurnal Time Response

Vehicle 9 - 7.0 Psi 

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-30

-20

-10

0

10

20

30

40

50

60

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6973

Low Temp Diurnal
 

97

Dynamic Diurnal

Vehicle 9 - 7.0 Psi

-30

-20

-10

0

10

20

30

40

50

60

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6973

Low Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 9 - 7.0 PSI

-500

0

500

1000

1500

2000

2500

3000

3500

4000

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Fuel Equivalent R134a

Actual R134a

Fuel Equivalent Methanol

Actual Methanol

Low Temp Diurnal

Test 6973
 

98 

Effect of Non-Fuel Contaminants

Vehicle 9 - 7.0 PSI

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

Low Temp Diurnal

Test 6973

Diurnal Time Response

Vehicle 9 - 7.0 Psi 

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 2 4 6 8 10 12 14 16 18 20 22 24

Test Time - hours

SHED AMbient Temperature - deg F

-10

0

10

20

30

40

50

60

70

80

90

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6974

High Temp Diurnal
 

99

Dynamic Diurnal

Vehicle 9 - 7.0 Psi

-10

0

10

20

30

40

50

60

70

80

90

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6974

High Temp Diurnal

Non-Fuel Contaminant Cumulative Permeation

Vehicle 9 - 7.0 PSI

0

50

100

150

200

250

300

350

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Fuel Equivalent R134a

Actual R134a

Fuel Equivalent Methanol

Actual Methanol

High Temp Diurnal

Test 6974
 

100 

Effect of Non-Fuel Contaminants

Vehicle 9 - 7.0 PSI

0

200

400

600

800

1000

1200

0 5 10 15 20 25

Test Time - hrs

Cumulative Permeation - mg

Raw SHED Mass

Corrected for R134a

Corrected for Methanol

Corrected SHED Mass

High Temp Diurnal

Test 6974

Cumulative Permeation - Corrected Mass

Vehicle 9

0

200

400

600

800

1000

1200

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

Lo Temp 7psi : Total SHED

Lo Temp 7psi : Non-Ethanol

Hi Temp : Total SHED

Hi Temp :Non-Ethanol

Ethanol Effect
 

101

1992 Toyota Camry SHED SHED

Results Results Canister

Permeation mg/day mg/day Loss

Veh Fuel Test Type Date Test# mg/hr (Raw) (Corrected) g

10 7.0 Static Perm 02/07/07 6977 80.5

Press. Incr. 13.2

Prs+Fuel Incr. 0.0

7.0 Dynamic RL 02/07/07 25648 1375.0

HS 977.1

RL + HS 2352.1

7.0 24 DHB 65-105 02/21/07 6984 3831.3 3773.7 0.00

Day 1 

7.0 24 DHB 65-105 02/23/07 6985 3150.4 3107.8 0.00

Day 1 

7.0 24 DHB 85-120 02/16/07 6983 1655.8 1689.3 4.98

Day 1 

Static 86 F Permeation

Vehicle 10 - 7 PSI

300

350

400

450

500

550

600

650

700

0 20 40 60 80 100 120

Test Time - minutes

Corrected SHED Mass - mg

Basic Permeation Rate at 86 80.5 mg/hr (1932 mg/day)

Incremental Incr. w/ pressurized tank 13.2 mg/hr

Incremental Incr. w/ Fuel Pump 'On' 0.0 mg/hr

Steady State

Permeation

Pressurize

the Tank

Power the

Fuel Pump 

Test 6977

Vehicle 10 
 

102 

Running Loss and Hot Soak

Vehicle 10 - 7 Psi

y = 0.4252x2 + 8.0915x

R2

 = 0.9989

y = -0.2872x2

 + 60.317x - 842.14

R2 = 0.9979

0

500

1000

1500

2000

2500

0 20 40 60 80 100 120

Test Time - minutes

Cumulative Permeation - mg

Test 25648

Running Loss Hot Soak

Running Loss Std. =0.05 g/mi

This Test = 0.025 g/mi

Diurnal Time Response

Vehicle 10 - 7 Psi

80 

85 

90 

95 

100 

105 

110 

115 

120 

125 

0 5 10 15 20 25

Test Time - hours

SHED AMbient Temperature - deg F

-50

0

50

100

150

200

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 
 

103

Dynamic Diurnal

Vehicle 10 - 7 Psi

-10

40

90

140

190

240

80 85 90 95 100 105 110 115 120 125 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6983

Diurnal Time Response

Vehicle 10 - 7 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25

Test Time - hours

SHED AMbient Temperature - deg F

-100

0

100

200

300

400

500

600

700

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6984
 

104 

Dynamic Diurnal

Vehicle 10 - 7 Psi

-100

0

100

200

300

400

500

600

700

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6984

Diurnal Time Response

Vehicle 10 - 7 Psi

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

110 

0 5 10 15 20 25

Test Time - hours

SHED AMbient Temperature - deg F

-100

0

100

200

300

400

500

600

Corrected Permeation - mg/hr

SHED Ambient

Hourly Permeation

Test 6984
 

105

Dynamic Diurnal

Vehicle 10 - 7 Psi

-100

0

100

200

300

400

500

600

60 70 80 90 100 110 

SHED Ambient temperature - deg F

Corrected Hourly Permeation - mg/hr

Test 6985

Cumulative Permeation

Vehicle 10

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 5 10 15 20 25

Test Time - hours

Cumulative Permeation - mg.

Low Temp - 7 Psi

Low Temp - 7 psi Repeat

High Temp - 7 psi