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 2003-01-2070 A Contribution to Understanding Automotive Fuel Economy and Its Limits Gino Sovran Troy, Michigan Dwight Blaser Washington, Michigan Government/Industry Meeting Washington, D.C. May 12-14, 2003Downloaded from SAE International by University of Minnesota, Tuesday, July 31, 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: [email protected]: 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 [email protected] ISSN 0148-7191Copyright © 2003 SAE International Positions 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 University of Minnesota, Tuesday, July 31, 20182003-01-2070 A Contribution to Understanding Automotive Fuel Economy and Its Limits Gino Sovran Troy, Michigan Dwight Blaser Washington, Michigan Copyright © 2003 SAE International ABSTRACT The fuel economy of an automobile is a highly complex function of the detailed characteristics of the vehicle and its subsystems (particularl y the engine, transmission and drivetrain), as well as being dependent on the manner in which the vehicle is driven. For existing vehicles, automotive manufacturers utilize laboratory test procedures to evaluate fuel economy. However, during new-vehicle design, and to assess the fuel economy potential of new technologies , computer programs that simulate the operation of the vehicle system over prescribed driving schedules are used. Of particular interest are the integrated fuel consumptions on the EPA Urban and Highway driving schedules since these are subject to Federal regulation. Since neither detailed subsystem test data nor simulation programs are typically used by those outsi de the automotive industry, the physics of fuel ec onomy is not always well understood. This paper presents the physics of motor vehicle fuel economy in an accurate, concise, and understandable form so that meaningful discussion/debate on the prospects for, and the limitations of, fuel economy improvements can be facilitated. INTRODUCTION Automotive fuel economy is again a national issue as the regulated Corporate Average Fuel Economy (CAFE) and the levels that must be achieved by automobile manufacturers are being debated. It is driven by a variety of concerns, including the following: 59% of the oil consumed in the U.S. in 2001 was imported (Ref. 1); the possibility of global warm ing and the contribution that CO 2 produced by motor vehicles might make to it; the environmental impact of exhaust emissions generated by road vehicles. About 44% of the oil used in the U.S. in 2001 was for motor gasoline (Ref. 1). This is primarily consumed by Light Duty Vehicles (LDVs), and these are the subjects of Federal fuel economy regulati on. The objective of this paper is to present the controlling physics of motor vehicle fuel economy in an accurate, concise and understandable form so that meaningful discussion/debate on the prospec ts for, and limi