Search Results

A survey is made of compression brake noise levels in heavy duty diesel trucks, using test procedures based on the ISO and EPA driveby acceleration noise tests. The data shows that compression brake noise levels are very high if worn out or open stack exhaust systems are used. Compression brake noise is also audible with OEM exhaust systems and, in at least one case, potentially objectionable. Two methods for reducing brake noise are investigated: improved mufflers and the use of an exhaust brake with the compression brake. Both techniques demonstrate a potential for reducing compression brake noise.

The EPA Heavy Truck Driveby Noise test is used to regulate trucks over 10,000 pounds GVW. The EPA test procedure is based on SAE J366. The EPA/J366 procedure is used both as a regulatory compliance tool and as a development tool. When the test procedure is used as a development tool, the goal is to determine the most cost effective means of meeting the legal requirement. Since J366 was not intended as a development tool, it can be difficult or misleading to use it to make decisions on product configuration. In order to use J366 successfully in vehicle or engine development, one must understand and properly account for the inherent variability of the J366 driveby test procedure. This paper examines both the extent and some of the sources of J366 driveby test variability. Strategies are proposed to ensure the proper interpretation of test results. Several repeat tests are required to accurately determine a small change in driveby noise level.

Reports of disabling diesel engine seal failures which accompanied the introduction of low sulfur diesel fuel in October '93 prompted an in-depth survey of diesel fuel chemical and physical properties. The purpose of the survey was to anticipate other possible problems which might arise with the newly introduced low sulfur fuels. The survey will produce a database containing over 1000 number 2 diesel fuels from various parts of the US. About 75% of the samples tested were on-highway low sulfur diesel fuels. Samples analyzed were from the D-A Lubricant Company, Cummins customers failures (truck fleets of various sizes), and a number of retail fueling stations. Properties under investigation are % Sulfur, Cloud/Pour Points, Viscosity, API Gravity, TAN/TBN, Boiling Range, Aromatics content, Heat Content, Lubricity, and Peroxide number.

Corrosive wear of non-ferrous engine components by lubricants is a concern of all major heavy duty diesel engine manufacturers since warranty on key engine components has been extended to 500,000 miles. Several commercial lubricants have been linked to premature cam and rod bearing failures induced by corrosion in certain fleets. Although the overall failure rate is low, specific fleets have experienced significantly higher failure rates due to the lubricants used. These failures usually occur at high mileages but less than 500,000 miles. This kind of slow corrosion easily escapes detection of engine tests contained in current oil specifications, and it represents a serious issue in long term warranty cost to diesel engine manufacturers. A comprehensive fleet database has been established to identify the most corrosive lubricants. These lubricants have served as reference oils to develop a corrosion bench test.

Data link interfaces are a very important part of the heavy duty vehicle industry; sharing information between subsystems is vital. SAE Recommended Practices J1708, J1587 and J1922 were developed to provide standards for proprietary communications, general information sharing, diagnostic definition and early powertrain controls. The industry realized, however, that these standards would not accomplish the ultimate goal-that of a high speed control and communications network. The development of more capable serial data communications for the heavy duty vehicle industry was prompted by the following: the desire of component suppliers to integrate subsystems for improved performance; the advancement of technology; customer expectations; and government regulations.

The continuing advances being made in microcomputer technology have resulted in its application to an ever increasing range of control systems. The improved performance and flexibility that would be achieved by a microcomputer based diesel engine fuel system cannot be matched by hydromechanical controls of the type currently used. Before an electronic system can be successfully introduced in the harsh heavy-duty truck environment, however, it must meet stringent reliability and durability goals at reasonable cost. This paper outlines some of the problems encountered and solutions implemented in the design of an electronic fuel pump for this market.