Alan C. Lloyd, Ph.D. Agency Secretary

The energy challenge facing California is real . Every Californian needs to take imm ediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs, see our Website: http://www.arb.ca.gov

. California Environmental Protection Agency

Printed on Recycled Paper 

# Air Resources Board

9480 Telstar Avenue, Suite 4 El Monte, California 91731 www.arb.ca.gov Arnold Schwarzenegge r Governor

June 22, 2005

MANUFACTURERS ADVISORY CORRESPONDENCE (MAC) 2005-03

TO: ALL PASSENGER CAR MANUFACTURERS
ALL LIGHT-DUTY TRUCK MANUFACTURERS
ALL MEDIUM-DUTY VEHICLE MANUFACTURERS
ALL OTHER INTERESTED PARTIES

SUBJECT: Optional Test Procedure For Certifying 2008 and Lat er Model-Year Gasoline-Fueled Zero-Fuel Evaporative Vehicles

This letter notifies industry that the Ai r Resources Board (ARB) has approved, with modifications, the test procedure proposed by the Alliance of Automobile Manufacturers (AAM) and the Association of International Automobile Manufacturers (AIAM) for certifying 2008 and later model-year (MY) gasoli ne vehicles to the optional zero-fuel evaporative emission standards. Beginning with MY2008, m anufacturers should use the procedure described in this MAC in lieu of the procedure outlined in MAC 2001-03 to demonstrate compliance with the zero-f uel evaporative emission standards. Other procedures may be used if approved, in advance, by the ARB.

In summary, the modifications to MAC 2001-03 include, use of 150,000 mile fuel evaporative emission level from rig tests as a deterioration factor for whole-vehicle evaporative emission standard compliance, we t and dry rig stabilization protocol, addition of manufacturer’s ARB-approv ed bench aging procedure to age wet rig, addition of ozone exposure pr otocol, policy clarifying the carry-over and carry-across of 2007 and earlier MY zero-fuel evaporative rig emission data to 2008 and subsequent MY, and reordering of rig test des cription for overall clarity.

The Exhaust/Evaporative Emissions Trading Fa ctors provided in MAC 2001-03 remain
valid for MY2008 and later vehicles. The trad ing factors remain at 0.1 grams per test (g/test) of evaporative emissions per 0. 002 grams per mile (g/mi) of exhaust non-methane organic gas (NMOG). The trading factors and calculations for determining
the factors are included in this MAC for ease of reference.

If you have any additional questions, please contact Ms. Rhonda Runyon, Staff,
On-Road Certification/Audit Sect ion, at (626) 575-6653 or at rrunyon@arb.ca.gov

.

Sincerely,

/s/

Allen Lyons, Chief Mobile Source Operations Division

Attachment2 STATE OF CALIFORNIA

AIR RESOURCES BOARD

MANUFACTURERS ADVISORY CO RRESPONDENCE (MAC) 2005-03

SUBJECT : Optional Test Procedure For Cert ifying 2008 and Later Model-Year Gasoline-Fueled Zero-Fuel Evaporative Vehicles

APPLICABILITY : 2008 and later model-year (MY) gaso line-fueled and gasoline-fueled hybrid electric passenger cars (PC) and light-duty trucks (LDT) certified to the optional zero-fuel ev aporative emission standards

REFERENCES:

1. Title 13, California Code of Regulations, (13 CCR) Section 1976,

"Standards and Test Procedures for Motor Vehicle Fuel Evaporative

Emissions."

2. "California Evaporat ive Emission Standards and Test Procedures for 2001 and Subsequent Model Motor Vehicles."

3. 13 CCR Section 1961, "Exhaust Emi ssion Standards and Test Procedures -- 2004 and Subsequent Model Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles."

4. "California Exhaust Emission St andards and Test Procedures for 2001 and Subsequent Model Passenger Ca rs, Light-Duty Trucks, and Medium-Duty Vehicles," Part II, A, 100.3.1.

5. MAC 2001-03 – “Optional Test Procedure for Certifying Pre-2005 Model-Year (MY) Gasoline Fueled Ze ro-Evaporative Vehicles and For Offsetting Evaporative And NMOG Emi ssions For Such Vehicles.”3 The following sections and topics will be presented in this MAC.

I. Background and Discussion

II. Whole-Vehicle Emissions Test Procedure Overview III. Fuel-Only Emissions Test Plan Overview A. Fuel System Rig Design B. Wet Rig Aging (Prior to Testing) C. Stabilization Preparat ion Events for the Wet Rig D. Wet and Dry Rig Stabiliza tion (Prior to Testing) IV. Fuel-Only Emissions Test Procedures A. Dry Rig Test #1 B. Wet Rig Test C. Dry Rig Test #2

V. Calculations VI. Carry-Over and Carry-Across VII. Exhaust/Evaporative Emissions Trading Factors A. Offset under 13 CCR 1976(b)(1)(E) B. Offset under 13 CCR 1961(a)(11)

I. BACKGROUND AND DISCUSSION

Title 13 CCR Section 1976 (b)(1)(E) es tablishes the optional zero-fuel evaporative emission standards fo r the three-day and two-day diurnal-plus-hot-soak (3D+HS and 2D+HS, respectively) tests, which are:

A. ”Whole vehicle”

• 0.35 grams per test (g/test ) hydrocarbons (HC) for PC;

• 0.50 g/test HC for LDT with a gross vehicle weight rating (GVWR) of

6000 pounds and under; and

• 0.75 g/test HC for LDT with a GVWR from over 6000 to 8500 pounds; and

B. ”Fuel-only”

Zero (0.0) g/test of HC fuel evaporative emissions.

In lieu of demonstrating compliance with the “fuel-only” zero (0.0) g/test of HC fuel evaporative emissions over the 3D +HS and 2D+HS tests, a manufacturer may submit, for advance ARB approval, a test plan to dem onstrate that the vehicle has zero (0.0) grams of HC f uel evaporative emissions throughout its useful life. Manufacturers have the opt ion of submitting for ARB approval an alternative test protocol demonstrating compliance with the zero-fuel evaporative emission requirements that is different from the one presented in this MAC.4 MAC 2001-03 provided guidance to manufactu rers for developing an interim test protocol to demonstrate zero evaporativ e emissions from the vehicle’s fuel system. Several issues identified in MAC 2001-03 needed furt her investigation by industry to resolve concerns raised by ARB staff with the test procedure the

MAC contains. Staff held several meet ings with industry in 2003 and 2004 to discuss a number of industry proposal s, including variations of the vehicle-minus-fuel system procedures, to re solve these concerns. During these discussions, manufacturers were allo wed to continue using MAC 2001-03 for certifying MY2005-2006 gasoline zero-fuel evaporative vehicl es. Ultimately, industry proposed a revised rig test for certifying MY2007 and later gasoline zero-fuel evaporative vehicles assuming accelerated approval by June, 2004.

While some of the ARB’s concerns are addr essed in this new protocol (e.g., aged parts, ozone exposure), other issues hav e not been fully resolved to staff’s satisfaction (e.g., rigorous permeati on stabilization procedure for permeable parts, and rigorous determination of repr esentative vapor losses from the air induction system and engine seals). Howeve r, in order to move forward with the improvements that have been id entified for certification of vehicles to the 2008 and subsequent zero-fuel evaporative emi ssion standards, the ARB is accepting the March 9, 2004, industry-pr oposed test protocol, with ce rtain modifications. The ARB may revise this guidance in the future if additional data become

available that warrant r eassessment of the test protocol and parameters

identified herein.

II. “WHOLE VEHICLE” EMISSION S TEST PROCEDURE OVERVIEW

To demonstrate compliance with the “whole vehicle” evaporative emission standards, manufacturers shall conduc t both the 3D+HS and 2D+HS test sequence with a vehicle that has been “ aged” to 15 years/150,000 (150K) miles useful life. Manufacturers may use their ARB-approved evaporative bench aging procedures or may propose alternat ives. When using bench aging, the degradation of the ev aporative emission control system must be equivalent to 15 years or 150K miles of customer us e. The 150K-mile fuel evaporative emission levels determined from rig testi ng may be used as the deterioration factors (DFs) when demonstrating co mpliance with the “whole-vehicle” evaporative emission standards.

If a manufacturer’s evaporative emission control system design includes an air induction system (AIS) carbon filter, the carbon element shall not be preconditioned nor shall it be removed from the vehicle during the vehicle preconditioning prior to the 3D+HS or 2D+H S tests. (The AIS filter, which is intended to control evaporative emissions during the hot soak portion of the evaporative test procedure, will have been purged completely once the vehicle is operating, hence no additional or s pecial preconditioning is allowed.)5 III. “FUEL-ONLY” EMISSIONS TEST PLAN OVERVIEW

The “fuel only” emissions test plan includes the testing of two fuel system rigs. One is never exposed to any fuel ("dry" rig), and the other is exposed to fuel ("wet" rig). These rigs shall undergo both 3D+HS and 2D+HS tests. However, manufacturers may provide an engineeri ng evaluation in lieu of conducting the 2D+HS test. If an engineerin g evaluation is used, it must include data showing

that the carbon canister’s st ate at the end of the vehicl e drive in the 2-day test sequence will be sufficient to control tw o days worth of diurnal emissions.

The results of the "dry" rig testing ar e used to determine non-fuel (background) HC emissions from rig components. The “d ry” rig’s results are then subtracted from the "wet" rig’s results to determine the total fuel-onl y evaporative emissions. The following procedures should be followed in the design and preparation of the rigs.

A. Fuel System Rig Design

Two rigs of identical design are assembl ed from the same batch of components. The manufacturer shall use good engineer ing judgment to ensure that the components included on the rigs cover all components that are exposed to liquid fuel or fuel vapor during the course of operation on a vehicle. Typically, these components include the fuel tank assembly (i ncluding the fill neck, fuel cap, fuel tank, and all tank fittings and valves), the fuel metering system (including the fuel pump/sender, fuel filt er, fuel lines, fuel rail assemb ly, pressure regulator, and fuel injectors), the fuel vapor control system (including all fuel vapor tube assemblies, the purge control valve, and the car bon canister assembly), and the AIS assembly of the engine (including the intake manifold, the air "breathing" tube, air filter assembly, and any fuel vapor control device in the AIS). Any "holes" that may be present in rig components that are a result of missing vehicle components (e.g., the "hole" in the inta ke manifold where the cylinder head is normally located) may be sealed before testing.

To make the rigs more easily trans portable, each rig may be supported on a movable fixture (e.g., tube metal or a portion of the vehicl e underbody). The lengths of metallic fuel lines may be reduced to allow the rig to be more compact. However, the dimensions of all fuel-pe rmeable components ar e to be production vehicle representative.6 B. “Wet” Rig Aging (Prior to Testing)

1. Fuel Injector Mechanical Operation

For the "wet" rig only, the fuel inje ctors must be aged to a 150K-mile test condition. This aging may be achiev ed by installing the injectors on a representative vehicle or engine and oper ating for 150K-mile equivalent, or by pulse cycling the injectors to a 150K-mile aged condition, using a bench aging procedure that has been approved by the ARB for this purpose.

2. Carbon Canister Purge/Load Cycling

For the "wet" rig only, the carbon cani ster must be aged to a 150K-mile test condition. This aging may be achiev ed by installing the canister on a representative vehicle and driving the v ehicle for 150K miles, or by cycling (loading and purging) the carbon cani ster to a 150K-mile aged condition, using a bench aging procedur e that has been approved by the ARB for this

purpose.

3. Other Critical Evapor ative Component Aging

For the "wet" rig only, besides the fuel injectors and carbon canister, all other rig components that a manufacturer bench ages for evaporative deterioration factor determination purposes shall be bench aged to a 150K-mile aged condition, using a bench aging procedure that has been approved by the ARB for establishing such DFs.

4. Ozone Exposure

Previously, manufacturers provided dat a to demonstrate the robustness of materials to ozone exposure for the equiva lent of 10 years of use by using ASTM test methods and exposure to 50-pphm ozone for 170 hours. Manufacturers may use the same protoc ol to demonstrate 15-year durability for materials vulnerable to ozone attack provided the exposure to ozone at 50 pphm is for 568 hours. This duration was determined based upon the cumulative ozone exposure expected for 15 years in the south coast air basin. Manufacturers may furnish a lis t of fuel system materials that are impervious to ozone or have demonstr ated durability to 15-year ozone exposure. These ozone-durable mate rials will not be required to undergo additional ozone durability demonst rations for certification.7 C. Stabilization Preparation Events for the "Wet" Rig

1. The aged fuel injectors shall be installed onto the rig (note: fuel injector seals may be replaced with new seals to ensure the injectors can be properly installed onto the rig).

2. The fuel tank shall be filled to a 40 percent nominal fill with California certification test fuel (as defined in Pa rt II, A, 100.3.1 in "California Exhaust

Emission Standards and Test Procedur es for 2001 and Subsequent Model Passenger Cars, Light-Duty Trucks, and Medium Duty Vehicles").

3. The fuel pump shall be operated to bl eed air out of the fuel rail and to expose the injectors to fuel. The bleed air may be vented, for example, through a special (non-production) service port on the fuel rail or through the fuel injectors.

4. The special fuel rail service port (if used) shall be sealed and the fuel pump operated momentarily to pre ssurize the fuel rail.

5. The intake manifold may be flushed with fresh air. (This also may be

conducted after stabilizati on, but before testing.)

D. “Wet” and “Dry” Rig Stabilization (Prior to Testing)

All components on both the "w et" and "dry" rigs shall be baked at a temperature of 40oC for 3360 hours (140 days) cumulative. The “wet” rig shall be baked while exposed to fuel or fuel vapor as appropr iate. Baking at higher temperatures (up to 60oC) for an accelerated duration is a cceptable, using the guideline that the time to reach stabilized permeation is acce lerated by a factor of two (2) for each

10 o C increase in soak temperature (about 7% acceleration for every 1 o C soak temperature increase). Other methods for accele rating the permeation stabilization process may be used with advance ARB approval. Manufacturers have the option of removing both the ca rbon canisters and AIS components prior to this stabilization period.

IV. “FUEL-ONLY” EMISSIONS TEST PROCEDURES

The California test fuel and temperatur es shall be used in all test procedures. Two separate “dry” rig tests shall be c onducted to address concerns with SHED background variability. The "dry" rig is test ed first, followed by "wet" rig testing, followed by repeat "dry" rig testing. All hot soak tests for bo th rigs are to be conducted in the same SHED, and the SHED may not be used for any other testing purposes between rig tests. All diurnal tests for both rigs are to be conducted in the same SHED, and the SHED may not be used for any other8 purposes between rig tests. The requireme nt to conduct tests in the same SHED may be waived if the manufacturer provides a compelling reason to do so. To request a waiver, the manufacturer must provide data for advance ARB approval demonstrating SHED-to-SHED corre lation of emission results.

A. "Dry" Rig Test #1

The stabilized "dry" rig shall undergo the 3D+HS and 2D+HS (if required) test procedures, including the required 6- to 36-hour soak between the hot soak and diurnal tests. All normally required vehicl e procedures prior to the hot soak test, such as fuel fills, preconditioning, ex haust and running loss tests, etc., may be eliminated from the pr ocedures. Only the first 24-hour diurnal period of the test procedure is required (i.e., the test may be stopped after 24 hours).

B. "Wet" Rig Test

The carbon canister from the st abilized and aged "wet" rig must be preconditioned to represent the st ate of the canister just pr ior to the hot soak test. This canister preconditioning may be achi eved by installing the canister on a representative vehicle and prepar ing the vehicle for the hot soak test (including a vehicle preconditioning drive, 300-bed-vo lume canister purge, appropriate canister load, cold and hot start exhaust tests, and, for the 3D+HS test sequence, a 105oF running loss test). Alternatively, the carbon canister preconditioning may be achieved by completing the following steps: 1) a 300-bed-volume canister purge, 2) appropriate canister load, and 3) a canister purge in a laboratory simulation, based on an engineering evaluat ion, to represent the net mass of

butane desorbed from the canist er during the drive cycle of the tests. This alternative method provides manufacturers flexibility fo r potential special cases in

which canister removal is difficult.

The "wet" rig shall be temperature soaked at the required test temperature for the six hours immediately precedi ng the hot soak test. The carbon canister may be disconnected from sources of fuel vapor du ring this temperature soak to maintain its preconditioned state; however, the cani ster shall be properly connected during the subsequent hot soak and diurnal tests. The fuel pump shall be operated momentarily to pressurize the fuel rail pr ior to the hot soak test. The "wet" rig shall undergo the procedures of the 3D+HS test, and, if required, the 2D+HS test, starting with the one-hour hot soak test and including the required

6- to 36-hour soak between the hot soak and diurnal tests. Manufacturers must rely on one of the three options below in order to demonstrate the heat load from the engine which is absent from the rig:9 1. Simulate Engine-C ompartment Temperature

At the beginning of the hot soak test, each fuel-permeable engine-compartment rig component will be heated to an elevated temperature. This elevated temperat ure used during this "pre-test heating" must be based on the engine-compartment temperature at the location of these components in a test vehicle at t he beginning of the hot soak test. If these engine-compartment component tem perature data are unavailable, a temperature of 220oF shall be used.

2. Additive Temperature Correction Factor

The "pre-test heating" described above ma y be excluded from the procedure

if the manufacturer su bmits data, based on good eng ineering judgment, to quantify the difference in hot soak te st data when comparing test data with and without the "pre-test heating." Th is quantity would then be added to the hot soak test data in which "pre-tes t" heating was not conducted, and used toward demonstrating compliance wit h the 0.0 grams HC standard. One acceptable method to determine this quantit y is to measure the difference in permeation of the fuel -permeable engine-compartment components (including their end connections) for one hour at tw o separate temperature conditions: (1) a constant temperature of 105oF, and (2) a temperature-time profile based on the temperatures these components are exposed to in a test vehicle during the hot soak test.

3. Engineering Evaluation of Temperature Effect

If the manufacturer has submitted dat a demonstrating that the difference between conducting and not conduc ting the "engine-compartment temperature” bake results in a negligible difference in emission measurements (that is, less than 2 mg durin g the hot soak test), then all fuel system components may be soaked at the test temperature.

C. "Dry" Rig Test #2

Following the completion of the “wet” rig test, the second te st of the “dry” rig shall be performed in the same manner as “dry ” rig test #1. (see A. above)

V. CALCULATIONS

A. Standard calculations for hot -soak and diurnal tests apply.

B. The “dry” rig’s D+HS HC evaporative emissi on shall be the mean of the “dry” rig’s test #1 and test #2 results. The “dry” rig’s D+HS emission level for each test is10 the sum of the HC emission level of the one-hour hot soak test and the 24-hour

diurnal test HC emission level.

C. "Wet" rig’s D+HS HC ev aporative emission is calcul ated as the sum of the

emission level of the one-hour hot soak test and the highest 24-hour emission level during the diurnal test. If "pre -test heating" of engine-compartment rig components is not conducted before the hot soak test, the factor developed according to section IV.B.2 (unless negligib le) shall be added to the hot soak test

data to account for the increase in permeation that would occur had the components been pre-heated.

D. Total fuel evaporative emissions sha ll be determined by subtracting the mean "dry" rig D+HS HC evaporative emissions value from the "wet" rig D+HS HC evaporative emissions value.

E. For rig testing, net enclosure volume is calculated by subtracting 5 cubic feet (or a manufacturer-determined rig volume that has received advance ARB approval)

from the enclosure volume.

F. The manufacturer may submit fuel evapor ative emission calculations for advance ARB approval if the test plan is expanded to include additional tests on the "dry" and "wet" rigs, as well as testing of mo re than one "dry" or "wet" rig.

G. Total fuel evaporative emissions less than or equal to 54 mg HC for both the 3D+HS and 2D+HS (if required) tests dem onstrate compliance with the optional zero-fuel evaporative emission standard.

VI. CARRY-OVER and CARRY-ACROSS

Subject to ARB approval, ca rry-over (C/O) and carry-acr oss (C/A) of zero-fuel evaporative emissions data used for MY 2007 and earlier certification may be allowed for MY2008 and subsequent certif ication. A C/O-C/A request must include an engineering ev aluation that assesses the impacts on measured evaporative emissions resulting from changes in the test protocols (data

determined under the MAC 2001-03 protocol versus the prot ocol in this MAC or other approved protocol). The engineeri ng evaluation must also address the impacts on evaporative emissions resulti ng from any differences between the current vehicle and the pre-MY2008 vehicle that provides the C/O-C/A emission

results.11 VII. EXHAUST/EVAPORATIVE EM ISSIONS TRADING FACTORS

Title 13, CCR Section 1976 (b)(1)(E) provid es manufacturers that are seeking partial zero-emission vehicle (PZEV) cr edits the option of having the measured fuel evaporative emissions reduced, in 0.1 gram HC incr ements, for all certification and in-use testing, if t he measured NMOG exhaust emissions for the vehicle are proportionately increased for a ll certification and in-use testing. Additionally, 13 CCR Section 1961(a)(11) allows an exhaust NMOG credit to be applied against the measured NMOG emissions in certification and in-use testing

for vehicles that were certified to t he zero-fuel evaporative standards but did not

seek a PZEV credit.

The ARB approved method for calculat ing the exhaust/evaporative emission trading factor for purposes of 13 CCR Section 1976(b)(1)(E) and 13 CCR Section 1961(a)(11) is explained bel ow. The calculations establish a trading factor of 0.1 g/test HC evapor ative emissions per 0.002 g/mi exhaust

NMOG emissions.

A. Offset Under 13 CCR 1976(b)(1)(E)

The LEV II regulations provide manufacture rs of vehicles seeking a partial ZEV credit with additional flexibility in comp lying with the zero-fuel evaporative emission standards, including the ability to offset a vehicle’s measured HC fuel evaporative emissions by proportionat ely adding NMOG emissions to the

vehicle’s exhaust emissions te st result. Manufacturers electing to use this option must offset the fuel evaporative emissi ons in 0.1 grams HC increments. The ARB staff has developed the following eq uation to calculate the appropriate

increase in a vehicle’s measured NM OG exhaust emissions for a corresponding 0.1 grams HC per test reduction in t he vehicle’s measured fuel evaporative

emissions:



### E exh 

### [g/mile] = E evap 

### [g/day] x F adj 

### D
ave 

### [mile/day]

Where:

E exh is the amount of NMOG emissions (to be added to the exhaust test emissions).

E evap is the amount of HC evaporativ e emissions (in 0.1 grams HC increment) (to be subtra cted from the fuel ev aporative emissions).

F adj is 0.67, a factor used to adjus t the certification evaporative temperature conditions to sout hcoast ozone planning temperature12 conditions (EMFAC 2000 model was used for calculating this adjustment factor).

D ave is 36 miles per day, the average vehi cle miles traveled per day in the

South Coast Air Basin.

Example 1 : Assume that a manufacturer is seeking to offset 0.1 grams HC per day of fuel evaporative emi ssions from a SULEV PC vehicle for which it is also seeking a PZEV credit. Then the followi ng amount of NMOG emissions would be

added to the vehicle’s exhaust test NMOG emissions:



### E exh 

### [g/mile] = 0.1 x 0.67 = 0.002 g/mile

36

Example 2 : Assume that the MY2007 SULEV PC vehicle in Example 1 above has the following emissions before offset s: 0.006 g/mi NM OG and 0.067 g/test fuel evaporative HC emissions during cert ification, and, a few years later, 0.009 g/mi NMOG and 0.078 g /test fuel evaporative HC emissions during in-use testing. Assume further that all other emissions of this vehicle comply with the

SULEV PC emission standards during certification and in-use testing. Apply the 0.002 g/mi for 0.1 g/te st offset. For certification purposes, this vehicle will be deemed as having the certification levels of 0.008 (=0.006+0.002) g/mi NMOG and –0.033 (=0.067-0.100) (cons idered 0.000) g/test fuel evaporative HC; the vehicle is qualified for and will be granted a PZEV credit. However, this vehicle will be deemed as having in-use emissi ons of 0.011 (=0.009+ 0.002) g/mi NMOG and -0.022 (=0.078-0.100) (considered 0.000) g/test fuel evaporative HC; the

vehicle has exceeded its in-use NMOG standard and is subject to corrective

actions.

B. Offset Under 13 CCR 1961(a)(11)

The LEV II regulations provide an NMOG offset factor, to be determined by the Executive Officer, for non-PZEV vehicles that are certified to the optional zero-fuel evaporative emission standard. This reactivity-adjusted offset factor is used for subtracting from the measured NMOG emissions during certification and in-use testing. The ARB staff has developed the NMOG of fset factor of 0.002 g/mi as follows.

The basic 0.002 g/mi NMOG per 0.1 g/test evaporative HC offset is the same as that developed for 13 CCR 1976(b)(E) abov e. The difference between the non-zero-fuel and optional zero-fuel evapor ative standards is 0.15 g/test. The

NMOG offset before reac tivity adjustment is, therefore, 0.003 g/mi (=0.002 * 0.15 / 0.1). Bec ause evaporative HC emissions are less reactive than exhaust NMOG emissions, ARB staff has determined that the reactivity-adjusted13 NMOG offset of 0.002 g/mi is appropriate for non-PZEV vehicles certified to the optional zero-fuel evapor ative emission standard.

Example 3 : Assume a MY2007 PC vehicle has 50,000- and 120,000-mile NMOG certification emissions of 0.041 and 0.050 g/ mi, respectively; all other emissions comply with the PC ULEV II standards. Furthermore, the manufacturer has elected to comply with the zero-fuel ev aporative standards. Apply the 0.002 g/mi

offset. The vehicle is then deemed as having 50,000- and 120,000-mile NMOG certification emissions of 0.039 (=0. 041-0.002) and 0.048 (=0.050-0.002) g/mi, respectively. The vehicle is therefore eligible to be certified to the ULEV II emission standards as request ed by the manufacturer.