OMS Advisory Circular May 1, 1987

United States Off ice of A/C No . 52A
Environmental Protection Air and Radiation Fade 1 of 5
A9enCV _ Wash.ng.on. DC 20460 _ May 1 1987

QMS

Advisory Circular
Subject;: EPA MVEL Laboratory Correlation

I. Purpose

The purpose of this advisory circular (A/C) is to describe to motor
vehicle manufacturers and motor vehicle manufacturers' associations the EPA
MVEL correlation policies that will be used to conduct correlation testing.

II. Background

This circular supercedes A/C No. 52 (January 20, 1976) and defines
guidelines for laboratory correlation.

III. Applicability

The provisions of this A/C are applicable to all light-duty vehicle
correlation programs which are requested either by manufacturer(s) ,
manufacturers' associations, or by EPA. Under the provisions of
§86.088-29(a)(3)(ii) and §600. 008-77 (g), EPA may reject manufacturer's test
data if an unacceptable level of correlation exists between the manufacturer
and EPA. Also, current EPA policy places increased emphasis on correlation
programs, in that results may be used to determine the number of certification
vehicles to receive confirmatory tests by EPA.

IV. Definitions

A. General Correlation Program - As used in this document, a general
correlation program is defined as a series of tests at a manufacturer's
laboratory and at EPA to establish confidence in test site equivalency and to
provide known relationships between EPA and the manufacturer's laboratory.
Testing may consist of, but is not limited to: diagnostics, statistical data
evaluation, calibration gas analyses, or emission testing.

B. Specific Correlation Program - As used in this document, a specific
correlation program is defined as a series of tests at a manufacturer's
laboratory and similar tests at EPA using a program plan designed to isolate
the cause of specific emission or fuel economy offsets. Testing may consist
of, but is not limited to: diagnostics, statistical data evaluation,
calibration gas analyses, or emission testing.

C. Manufacturers' Association - A manufacturers' association is
defined as a national or international organization which has been recognized
by EPA to represent geographic areas or other common interests. Examples of
manufacturers' associations include: MVMA (Motor Vehicle Manufacturers
Association of the U.S.) and JAMA (Japan Automobile Manufacturers Association).

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U.S. Environmental OAR/OMS A/C NO. 52A
P’otection Agency PAGE 2 OF 5
V. EPA Correlation Program Policies
A. EPA or Nanufacturer Requested Programs - To ensure that an
acceptable level of correlation exists, general or specific correlation
programs may be conduc ted for the following reasons:
1. Paired data offsets and correlation uncertainty.
2. Changes in testing procedures or equipment.
3. Changes in the emission standards or the regulation of new
emission constituents.
B. General Correlation Program - General correlation programs
involving EPA will be conducted, unless otherwise agreed upon, using the
procedural outline described in Standard Programs (Part VI of this A/C) and
the following guidelines:
1. All requests for general correlation programs will be
submitted in writing to the Director of the Engineering Operations Division
before the start of any tests. Each request should include the following
information:
a) Purpose of the program.
b) The manufacturer’s laboratories to be involved.
c) A test plan, subject to EPA approval, which includes:
— the number and types of tests.
— the number and types of vehicles.
— the information expected from each type of test.
d) Preferred and acceptable dates of testing at EPA.
2. Because of the inherent efficiency, priority will be given to
correlation programs which involve a number of laboratories.
3. Priority will also be given to those programs which use
“instrumented” test vehicles. The required instrumentation is specified in
Part VI.B.l. of this A/C.
4. Bequests for general correlation programs from individual
manufacturers not represented in multiple manufacturer correlation activities
will also be considered if the rationale and justification why the program is
not being requested in coordination with other manufacturers is presented.
However, the allocation of EPA laboratory time . to any such individual programs
must on an “as available” basis, and sometimes may not be possible.
Barring . unusual circumstances, it is intended that any general correlation
study with an individual manufacturer will be limited to once a year, and two
correlation vehicles.

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U.S. Environmental OAR/OMS A/C NO. 52A
oEPA P’otection Agency PAGE OF 5
5. As a supplement to all correlation activities, manufacturers
may be required to submit data to EPA describing their equipment which
includes, but is not limited to: dynamometer, CVS, gas analysis system, air
handling, soak area, evaporative emission measurement equipment, particulate
measurement equipment, vehicle cooling system (fans), driver’s aid, data
reduction, data validation, calibration gas, test procedures, fuel analysis,
training, and computer programs. Diagnostic data may be requested immediately
before and after the correlation program.
6. EPA may determine that other checks may be required to provide
information to determine the reasons for an offset, including data on
manufacturers’ intra-labora tory correlation.
7. When scheduling a correlation program among a number of
laboratories, testing at EPA shall be scheduled last before returning to the
sponsoring laboratory for final testing. Variations from this policy will be
allowed only if it is necessary for improved testing efficiency.
8. Complete vehicle information (i.e., the information requested
on the “Vehicle Information Data Sheet,” Attachment I) is required at least a
week prior to any testing at EPA. Prior to conducting any correlation tests
at EPA, all data from similar tests at the manufacturer’s laboratories will be
submitted to EPA. Final test data must be submitted within ten days of the
last test from a correlation program with an individual laboratory.
Manufacturers’ association final test data shall be submitted to EPA no later
than fifteen days from the completion of testing. All data shall be submitted
using the “Manufacturer’s Laboratory Correlation Data Sheet,” Attachment II.
All relevant raw data (i.e., sample and background concentrations for test
phases, ambient conditions data, CVS data, test site identification, and
driver) may be requested in addition to the usual composite test results. In
general, data from all participating laboratories will be required prior to
the release of any correlation results by EPA.
9. One week of laboratory testing at MVEL is considered an
adequate period of time for any participant in a correlation program. It is
requested that all single manufacturer correlation tests be executed and
concluded as soon as reasonably possible, but always within a one—month
period. Manufacturers’ associations’ general correlation programs are to be
completed in a timely fashion , dependent on the number of laboratories
included in the program. -
C. Specific Correlation Programs
1. Requests for specific correlation programs will be submitted
in writing to the Director of the Engineering Operations Division and will be
evaluated individually. A specific correlation program may be scheduled as a
result of a general correlation program or from an individual request only if:

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U.S. Environmental OAR/OMS A/C NO. 52A
oEPA Protection Agency PAGE 4 OF 5
a. The manufacturers can demonstrate, and EPA agrees, that
there is a significant emission or fuel economy offset.
b. The manufacturer has thoroughly investigated the cause of
these differences and can find no reason for the correlation problem. The
request will include:
1) A list of what was investigated.
2) The reasons these items were investigated.
3) Any data generated.
4) A summary of the results and any conclusions drawn.
c. The manufacturer adequately demonstrates that tests at
EPA will be necessary to isolate the cause of the specific correlation problem.
2. EPA may request specific correlation programs when
circumstances warrant such a program.
3. Specific correlation programs involving EPA, while tailored
from the outline described in Standard Programs (Part VI of this A/C), will be
designed to address the manufacturer’s specific correlation problem. The
guidelines which describe test priority, reporting of supplemental
information, submission of intra—laboratory data, data entry forms, and test
time allocation are the same as those described in Part B, General Correlation
Programs, Sections 3, 5, 6, 8 and 9.
VI. Standard Programs
The events associated with a general correlation program and, if
appropriate, specific correlation programs, are shown in Figure 1, the
Correlation Flow Chart. This chart is a guideline showing the sequence of
events which occur during a typical correlation program. Each correlation
program is unique, and therefore certain programs will dictate that EPA be
flexible in its adherence to this flowchart. Deviations from this chart will
be permitted to enhance the effectiveness and efficiency of a particular
correlation program.
A. Testing — The actual test design will vary depending upon the
purpose of the general or specific correlation program.
B. Vehicle — Vehicle(s) shall be submitted for testing as follows:
1. Baseline tests must be conducted on the vehicle(s) to
establish stabilization before the program begins at the manufacturer’s
laboratory. The number of baseline tests will be a function of the test
repeatability. An assessment of the baseline adequacy will be made by EPA.

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U.S. Environmental OAR/OMS A/C NO. 52A
SEPA P’otection Agency PAGE_ 5 OF 5
2. Because fuel flow measurements and total cumulative torque
measurements are valuable diagnostic tools for analyzing correlation
anomalies, EPA requests that all vehicles submitted for testing be equipped
‘with a temperature compensated fuel flow measurement system and a totalizing
wheel torque measurement system. The fuel flow measurement system shall be
capable of providing volumetric or mass fuel flow measurements for individual
test phases. The torque measurement system should totalize positive and
negative torque separately for each phase of the driving cycle.
3. It is further recommended that all electronic measurement and
recording equipment be installed in and remain with the vehicle throughout its
test program to minimize measurement discrepancies caused by differences in
equipment type, calibration, etc. All equipment is to be designed to operate
on 120v, 60HZ AC current, or from the vehicle’s power.
C. Analysis — The program evaluation will be based on appropriate
statistical analysis to test for the existence of significant differences
among test sites and test conditions. The factors of interest include, but
are not limited to: test site equipment, time, ambient test conditions,
vehicle repeatability, and phase and composite emission and fuel economy
values. Other variables will be analyzed where, in EPA’s judgment, they are
re qui it d.
VII. Reports
A report summarizing the results of the general or specific correlation
program shall be prepared by the individual manufacturer or the manufacturers’
association and submitted to the Director of the Engineering Operations
Division. The report should be submitted within four weeks of final testing
for an individual manufacturer and within eight weeks of final testing for an
association.
EPA will analyze the results of all general and specific correlation
programs after all the manufacturer’s data are received. When the results of
a correlation program warrants an EPA prepared report, one will be prepared
and made available to the public. In addition, a copy will be forwarded to
the Director of the Certification Division for further action as required.
tirector, es
Attachments
‘7
fice of Mobile
0643c

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Figure 1
Correlation Flow Chart
EPA Data Analysis and
Report if Required
DDV 3/5/87

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