400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2003-01-3438 “The Influence of Idle, Drive Cycle and Accessories on the Fuel Economy of Urban Hybrid Electric Buses – Chassis Dynamometer Tests” Edward Bass and Timothy Alfermann Allison Transmission General Motors Corporation 2003 SAE International Truck and Bus Meeting and Exhibition Fort Worth, Texas November 10-12, 2003Downloaded from SAE International by Univ of California Berkeley, Thursday, July 26, 2018All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: permissions@sae.orgFax: 724-772-4891Tel: 724-772-4028 For multiple print copies contact: SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: Customer Service@sae.org ISSN 0148-7191Copyright © 2003 SAE InternationalPositions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE.The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the pap er if it is publishe d in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send themanuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by Univ of California Berkeley, Thursday, July 26, 20181ABSTRACT Fuel economy can be part of a business case for a fleet making the decision to buy new HD hybriddrivetrain technologies. Chassis dynamometer testsusing SAE Recommended Practice J2711 on a busequipped with an Allison E P SYSTEM TMhybrid system and operated on standard bus driving cycles haveproduced impressive gains of over 60%. Preliminaryurban bus field tests, on the other hand, have shownlower fuel economy gains. The difference can beattributed, in part, to the use of accessories - mostimportantly air conditioning - which are parasitic loadson the vehicle. In this paper the characteristics ofdriving cycles are studied to determine those factorswhich have the strongest influence on fuel economy forhybrids. The data show that the number of stoppingevents in a route or cycle is a strong influence as is theaverage vehicle speed. Energy analysis will show therelationship of fuel economy benefit and battery energywithin a driving cycle. Transit managers can use thisinformation to get the most from the hybrid vehicles intheir fleet by assigning them to the most effectiveroutes. INTRODUCTION In 1998 General Motors Corporation launched an initiative to develop hybrid-electric propulsion systems for heavy-duty vehicles in urban vocations of class 3 through 8 vehicles. The propulsion system that has emerged, the Allison EP SYSTEMTM, is a patented, two-mode, compound-split, parallel hybrid-electric drivethat combines power from both an advanced nickel- metal hydride (NiMH) battery energy storage system (ESS) and a clean diesel engine. Production is currently underway. The targeted applications for the release of the product are transit buses and coaches that operate in congested urban areas. LAB DYNAMOMETER TESTS Independent laboratory tests, using SAE Recommended Practice J2711(1), have demonstrated the emissions and fuel economy (FE) benefits of thistechnology. These benefits are made possible by the EP SYSTEMTMin several ways: buffering the engine from transients, decoupling the engine from road load,and by reducing the work or energy required from the engine. This study will concentrate on the last of these hybrid attributes. Fuel economy