Title: Application of semi-direct injection for spark-ignition engine

Authors: Yuh-Yih Wu, Bo-Chiuan Chen, Anh-Trung Tran

Addresses: Department of Vehicle Engineering, National Taipei University of Technology, No. 1, Sec. 3, Jhongsiao E. Rd., Taipei 10608, Taiwan. ' Department of Vehicle Engineering, National Taipei University of Technology, No. 1, Sec. 3, Jhongsiao E. Rd., Taipei 10608, Taiwan. ' Department of Vehicle Engineering, National Taipei University of Technology, No. 1, Sec. 3, Jhongsiao E. Rd., Taipei 10608, Taiwan

Abstract: This paper proposes an application of a motorcycle engine lean-burn system for improving engine efficiency and reducing exhaust emissions. This Semi-Direct Injection (SDI) system consists of a high swirl charge, injection during intake-valve opening, and air-assisted fuel injection. The fuel enters the cylinder directly through the intake valve near the middle intake stroke for a richer mixture around the spark plug. A 125 cc, 4-valve, Port-Fuel-Injection (PFI) engine was retrofitted by designing a control plate to enhance the swirl. The swirl ratio was increased to 3.8 and the lean limit was extended to 1.7 of lambda (excess air ratio). The engine was tested at the low-load region, which includes most operation points of the ECE-40 driving cycle. A complete engine performance map was conducted for comparison between SDI and original PFI engines. The results show that Brake-Specific Fuel Consumption (BSFC) decreased by 11.3%. Brake-specific exhaust emissions of NOx and CO decreased by 32.0% and 92.9%, respectively. The HC emission increased by 47.7%.

Keywords: motorcycles; motorbikes; SI engines; lean burn; air-assisted fuel injection; semi-direct injection; spark ignition; motorcycle engines; engine efficiency; exhaust emissions; vehicle design; fuel consumption.

DOI: 10.1504/IJVD.2010.036841

International Journal of Vehicle Design, 2010 Vol.54 No.4, pp.356 - 370

Received: 31 Dec 2009
Accepted: 11 Jun 2010

Published online: 12 Nov 2010 *

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