July 8, 2015

MEMORANDUM

SUBJECT:	A bug fixed in GEM manual transmission efficiency

FROM:	Houshun Zhang, OTAQ/ASD

TO:	Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles - Phase 2 - Docket EPA-HQ-OAR-xxxx-yyyy


A bug was identified recently in calculating the manual transmission mechanical efficiency.  In the GEM design, it is supposed that all gear mechanical efficiency should be set to 96% except the direct drive ratio with 1:1, which should be set to 98%.  However, GEM was set 98% to gear ratio number less than 1, and all others are 96%.  This is incorrect.  Consequently, the modification on GEM was conducted, making sure that only gear ratio of 1:1 is set to 98% and all others are 96%.  

It should be pointed out that this bug only affects the manual transmission and it doesn't affect all of other transmissions. 



