Implementation of engine turn off at idle is desirable to gain improvements in vehicle fuel economy. There are a number of alternatives for implementation of the restarting function, including the existing cranking motor, a 12V or 36V belt-starter, a crankshaft integrated-startergenerator (ISG), and other, more complex hybrid powertrain architectures. Of these options, the 12V belt-alternator-starter (BAS) offers strong potential for fast, quiet starting at a lower system cost and complexity than higher-power 36V alternatives. Two challenges are 1) the need to accelerate a large engine to idle speed quickly, and 2) dynamic torque control during the start for smoothness. In the absence of a higher power electrical machine to accomplish these tasks, combustion- assisted starting has been studied as a potential method of aiding a 12V accessory drive belt-alternator-starter in the starting process on larger engines. Approximately 4-6 % of the fuel economy advantage with many hybrids is due to an Idle Engine Off (IEO) strategy, which shuts the engine off under conditions where it would normally be idling. The engine is restarted as soon as the driver requests torque by, for instance, pressing the accelerator, or on command from the Electronic Control Module (ECM) based on other restart criteria. A cost effective option to only take advantage of the IEO would be using a lower' power belt starter/generator, (SG), which replaces the standard alternator and is mounted on the same location. An Energen 5 High Output BAS development unit from Delphi was selected to be applied to a GM V8 5.3L engine. For this study, the system was installed on a Chevrolet Silverado truck and evaluated for design feasibility, driveability, and emissions over the US FTP cycle. The combustion-assisted cranking system has been implemented on a 5.3L V-8 engine with automatic transmission in a full-size truck. Integration of the BAS system controls with powertrain fuel and spark management shows the importance of combustion-assist within the first several compression events. The use of a cylinder-event-based (CEB) spark strategy was found to benefit the feel of auto-starts, as measured by passenger seat track vibrations. Introducing fuel into the cylinders during the shutdown showed up to 40% improvement in engine start times. Furthermore, this paper reports the feasibility of auto-starts from shutdown fuel in terms of start consistency and shows the need for a quick synchronization process of the powertrain control module if a 12-volt system is to be successfully used.


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    Title :

    Combustion assisted belt-cranking of a V-8 engine at 12-Volts


    Additional title:

    Kraftstoffunterstütztes riemenangetriebenes Anlassen eines V-8-Motors bei 12 V


    Contributors:


    Publication date :

    2004


    Size :

    12 Seiten, 29 Bilder, 3 Tabellen, 3 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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