Development and Testing of Optimized Engine Oils for Modern Two-Stroke Cycle, Direct-Fuel-Injected Outboard Engines

摘要

Despite the recent increase in fuel prices, the multibillion dollar recreational boating market in North America continues to experience solid momentum and growth. In the U.S. economy alone, sales of recreational boats continue to increase with over 17 million boats sold in 2004. Of that share, outboard boats and the engines that power them, accounted for nearly half of all boat sales. Though there has been a shift in outboard technology to four-stroke cycle engines, a significant number of new engine sales represent two-stroke cycle engines employing direct fuel injection as a means to meet emissions regulations. With the life span of modern outboards estimated to be 8 to 10 years, a significant base of two-stroke cycle engines exist in the market place, and will continue to do so for the foreseeable future. Most of the major original equipment manufacturers (OEMs) offer a choice of engine technology to meet emissions regulations in the form of four-stroke or direct-fuel-injected (DFI), two-stroke cycle engines, with both segments representing a near equal share of the large engine market. Since the first DFI two-stroke cycle engines were introduced in the mid to late 1990's, significant strides have been made in further improving engine performance. However, the move from conventional carbureted two-stroke cycle engines to DFI technology introduced a more severe environment for the engine lubricant. With the advent of DFI, overall engine operating temperatures have increased resulting in greater demands being imposed on the engine's lubricant. In some severe duty applications, field problems have been experienced with some outboard engine oils leading to excessive liner wear and even engine scuffing. To address this deficiency, lubricant formulations were developed and a laboratory engine test procedure was designed to quickly simulate and replicate observed field conditions. The test protocol allowed for quick screening of candidate formulations with improved overall engine performance. To validate the results, field trials were conducted under severe real-world conditions. In summary, the established test protocol and methodology allowed for the rapid development of new and improved formulations for modern two-stroke cycle DFI outboard engines.