March 9,1999
   
   
   Document Released for Stakeholder Review and
Comment
   
   Exhaust Emission Temperature Correction Factors
for   MOBILE6:  Engine Start and Running LA4
Emissions for   Gasoline Vehicles
   
   EPA Publication Number EPA420-P-99-001
   
   MOBILE6 Report Number M6.STE.004
   
        The Office of Mobile Sources, Assessment
and Modeling   Division, announces the release of
"Exhaust Emission   Temperature Correction Factors
for MOBILE6:  Engine Start   and Running LA4
Emissions for Gasoline Vehicles" for   stakeholder
review and comment.  This document  
M6STE004.PDF/M6STE004.WPD is available at the
MOBILE6   section of the OMS Web Site:
        (http://www.epa.gov/omswww/models.htm).
   
        For MOBILE6, the existing MOBILE5
temperature   correction factors will still be
used.  However, they will   be applied separately
to cold start, hot start, and running   LA4
emissions rather than weighted together into an
overall   FTP correction using the operating mode
temperature   correction factor inputs like in
MOBILE5.  For MOBILE6, the   Bag1 temperature
correction factor will be applied to the   cold
start emissions (a 12 hour soak prior the start). 
The   Bag3 temperature correction factor will be
applied to the   hot start emissions (a 10 minute
soak prior to the start).    A VMT weighted
combination of Bag2 and Bag3 temperature  
correction factor will be applied to the running
LA4   emissions.  Linear interpolation between the
hot start (10   minute soak) and the cold start
(12 hour soak) will be done   to obtain
temperature correction factors for starts with  
soaks in between these two values.
   
        The document also describes the
methodology and data   used to update the effects
of the new Phase1 cold   temperature CO standard. 
The data which were used are from   a sample of
1997 model year vehicles certified to the  
tighter cold CO standards.  An improved
methodology is also   discussed in the document to
fix an inconsistency in the   MOBILE5b code in the
handling of cold temperature CO   emissions in the
event that a tighter Phase 2 cold   temperature
standard is implemented.
   
        Comments on this report and its proposed
use in   MOBILE6 should be sent to the attention
of Ed Glover.    Comments may be submitted
electronically to   mobile@epamail.epa.gov, or by
fax to (734) 214-4939, or by   mail to "MOBILE6
Review Comments", US EPA Assessment and   Modeling
Division, 2000 Traverwood Drive, Ann Arbor MI 48105.  
 Electronic submission of comments is preferred. 
In your   comments, please note clearly the
document that you are   commenting on including
the report title and the code   number listed.
Please be sure to include your name,   address,
affiliation, and any other pertinent information.
   
   This document is being released and posted in
on March 9,1999.  Comments will be accepted for
sixty (60) days,   ending May 10, 1999  EPA will
then review and consider all   comments received,
and will provide a summary of those   comments and
how we are responding to them in the form of a  
followup document after the close of the comment
period.
                              
   Thank you for your continuing interest in the
development   of MOBILE6.
   
   Sincerely,
   
Emission Inventory Group, Assessment and Modeling
Division
US EPA Office of Mobile Sources