Abstract:
Engine reconfiguration kits are developed for NOx emission reduction in Electro-Motive Division of General Motors Corporation model 645 diesel engines. The kits feature improved unit fuel injectors providing better fuel atomization with retarded injection timing and other improvements. Included new higher efficiency four pass counterflow aftercoolers provide reduced airbox inlet air temperatures. New connector pipes for the counterflow aftercoolers may also be included. Optional higher compression ratio pistons are available for increased fuel efficiency in some engine types. The kits reduce NOx emissions without increasing smoke, CO or particulate emissions or reducing performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/434,860 filed Dec. 19, 2002. 

   TECHNICAL FIELD 
   This invention relates to Electro-Motive Division (EMD) of General Motors Corporation model 645 two-cycle diesel engines and, more particularly, to emission reduction kits for such engines. 
   BACKGROUND OF THE INVENTION 
   In response to a United States Environmental Protection Agency requirement, EMD has developed a family of kits including components to be substituted for the corresponding components originally provided with various types of 645 model engines in order to meet a requirement for reduced emission of nitrogen oxides (NOx). It is known that NOx emissions can be reduced by retarding fuel injection timing. However, this generally leads to an increase in smoke, CO and particulate emissions. It is also known that reducing engine airbox temperature contributes to lower NOx emissions. Previously, the 645 model engines had used two pass parallel flow aftercoolers. However, improved four pass counterflow aftercoolers were known to provide reduced airbox temperatures. 
   SUMMARY OF THE INVENTION 
   In order to meet the EPA requirements, approximately two dozen separate kits have been developed containing replacement components for model 645FB, 645E3B and EC3 and 645E3 engines, as well as 645E and 645E-SW engines. 
   In general, the E-SW switcher models required only changes in the injectors to meet the requirements. The 645E models required new injectors and a replacement oil separator element. For the remaining models, the kits all included substantially improved unit fuel injectors and four pass counterflow aftercoolers replacing the original components. 
   A basic feature of the kits is inclusion of a pin stack-low sac injector nozzle designed by Interstate-McBee to timing retard specifications provided by EMD. The following commonly assigned United States patents cover various features of these injectors: U.S. Pat. No. 6,321,723B1 issued Nov. 27, 2001; U.S. Pat. No. 6,012,433 issued Jan. 11, 2000; U.S. Pat. No. 6,007,000 issued Dec. 28, 1999; U.S. Pat. No. 5,797,427 issued Aug. 25, 1998; U.S. Pat. No. 5,725,157 issued Mar. 10, 1998 and U.S. Pat. No. 5,467,924 issued Nov. 21, 1995. The disclosures of all these issued patents are incorporated by reference in this application. 
   Additional basic features of the kits are higher efficiency four pass counterflow aftercoolers which replace the two pass parallel flow aftercoolers of the previous model 645 engines. The number of fins in the aftercooler cores has also been increased to provide better cooling efficiency. The new aftercoolers are effective to lower airbox temperatures by approximately 20% and NOx emissions by about 7% compared to the original aftercoolers. The kits also include revised pipes for connecting new aftercoolers into the engine cooling system. 
   For the E3B type engines, an alternate fuel package is also available which includes, in addition to the injectors and counterflow aftercoolers, higher compression ratio pistons. These increase the cylinder compression ratio from about 14.5 to about 16 to 1. This package provides improved fuel efficiency for the engines while continuing to meet the requirements of the new regulations. 
   These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary cross-sectional view of a prior art EMD model 645 engine showing the left bank aftercooler and a cylinder unit injector; 
       FIG. 2  is a transverse cross-sectional view of the engine of  FIG. 1 ; 
       FIG. 3  is a side view showing connections of the right bank aftercooler to the engine cooling system; 
       FIG. 4  is a top view of the aftercooler pipe connections; 
       FIG. 5  is an end view of the aftercooler pipe connections; and 
       FIG. 6  is a schematic cross-sectional view of a four pass counterflow aftercooler according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIGS. 1 and 2  of the drawings, numeral  10  generally indicates an EMD model 645 two cycle diesel engine. Engine  10  includes a crankcase  12  including two banks  14  of longitudinally aligned cylinders  16 . The crankcase  12  further defines right and left bank airboxes  18  which are pressurized to provide scavenging and charging air to the cylinders  16  through ports  20  formed in cylinder liners  22 . Individual cylinder heads  24  are fixed to the tops of the liners  22  and include exhaust valves  26  for controlling the exhaust of combustion products from the cylinders. Each head also carries a fuel injector  28  for injecting diesel fuel into the cylinders in accordance with a predetermined injection timing setting. 
   The injectors are mechanically actuated unit injectors wherein a plunger actuated by a camshaft and rocker arm is reciprocated to inject fuel at a predetermined timing setting. The volume of fuel injected each stroke and the time of injection is controlled by a helix on the plunger which is rotated by a mechanically actuated rack to control the proper amount and timing of the fuel injected at each piston stroke. Further details of the operation of the injectors and their various features are described in the previously mentioned United States patents, which have been incorporated herein by reference. 
   The engine has a cooling system  29 , which includes coolant manifolds  30  extending longitudinally through each of the airboxes  18 . The coolant manifolds are connected to the cylinder liners for providing coolant for cooling the engine cylinders during operation. External radiators, not shown, cool the heated coolant, which is pumped through the manifolds  30  by engine mounted water pumps, not shown. 
   As shown in  FIG. 1 , the engine also includes a turbocharger  32  mounted on the engine crankcase and driven in part by a mechanical gear train and by engine exhaust gases. The turbocharger  32  delivers pressurized air to the engine airboxes  18  for scavenging and charging the cylinders. 
   Between the turbocharger compressor outlets, not shown, and each of the engine airboxes  18 , there is mounted an aftercooler  34 , one for each bank of cylinders. The aftercoolers  34  are connected with the coolant manifolds  30 , which provide the aftercoolers with cooling water for cooling the inlet air delivered to the engine airboxes from the turbocharger. 
   Referring next to  FIGS. 3-5 , there are shown respectively side, top and end views of the portions of the engine cooling system which connect with the aftercoolers  34 . At the rear face of the engine crankcase, right and left bank feed pipes  36 ,  38  are connected between the coolant manifolds  30  and inlet ports  40 , located at the bottom of each manifold header  42  and offset toward the engine side of the respective aftercooler  34 . At upper ends of the headers  42 , return pipes  44 ,  46  are connected between an outlet port  48  at the end of each header farthest from the engine to a return connector  50  that returns cooling water to a coolant gallery  52  in the crankcase between the engine cylinder banks. 
   Referring now to  FIG. 6  of the drawings, there is shown schematically an operational view of the interior of one of the aftercoolers  34 . Each aftercooler includes a core  54 , which is open at opposite ends for the passage of air flow in the direction of the arrows  56 . In the new aftercooler core  54 , the fin-tube fin density has been increased from 11 to 16 fins per inch to provide more efficient cooling of the air passing through the core. 
   On the sides of the core are provided a main header  58  and a return header  60 . The headers  58 ,  60  are arranged to divide the water tubes  62  of the core into four groups which provide first, second, third and fourth passes  64 ,  66 ,  68  and  70  for water flow through the core from the inlet port  40  to the outlet port  48 . The main header is provided with dual inlet ports  40  and dual outlet ports  48  so that the aftercooler may be installed on either side of the engine. 
   The arrangement defines a four pass counterflow aftercooler wherein air flow passing through the core first contacts the last pass  70 , which has the warmest water, and then contacts sequentially passes  68  and  66 , passing last through the first pass  64  which carries the coolest water. With this arrangement, maximum cooling of the charging air for the engine cylinders is obtained since the charging air is last in cooling communication with the first pass of the aftercooler which carries the coolest water. 
   For non-turbocharged engines, some of the SW kits only require new injectors. The 645E kits additionally require new oil separator elements as well as new injectors. The remaining kits for turbocharged engines all include new injectors and the new four pass counterflow aftercoolers  34 , previously described, as well as new counterflow pipes  36 ,  38 ,  44 ,  46  for connecting the aftercoolers into the engine cooling system. A special fuel package for the E3B engines includes higher output injectors and new pistons which increase the engine cylinder compression ratio to about 16 to 1 from the 14 to 1 compression ratio of the original engines. 
   In operation of the 645 engines modified by their respective kits, the injection timing is retarded by an average of about 4-6 degrees of crankshaft rotation which reduces the formation of NOx in the engine cylinders. The high injection pressure and better atomization of the fuel provided by the new injectors avoids increasing of smoke, CO emissions and particulates in the combustion process. The counterflow arrangement and increased fin density of the four pass aftercoolers results in a reduction of airbox temperatures of about 20% with the resulting lowering of NOx emissions by about 7% compared to the original aftercoolers. 
   The aftercoolers are sized to fit into the same space occupied by the original two pass aftercoolers and the fuel injectors are designed to fit into the same space occupied by the original unit injectors. Further the injector design is such that setting of injector timing by the engine mechanic can be done with exactly the same tools and settings utilized with the original injectors so that no confusion arises as to the setting of the injector timing with the new injectors. Internal features of the injectors include reduced needle valve weight, smaller fuel volume between the needle valve and the internal plunger and reduced sac volume below the needle as compared to the original injectors. These features all assist in providing the improved combustion and reduced emissions which the injectors assist in providing. 
   The replacement pipes for connecting the aftercoolers with the engine are designed to be easily assembled into the engine with the aftercoolers themselves. The replacement pistons utilized in the special fuel package for E3B engines provides a compression ratio increase which provides better fuel efficiency for the engines involved. The piston crown configurations are designed to match the injector characteristics so as to provide a maximum of operating efficiency and power production. 
   The selection, development and evaluation of the new engine components including the improved fuel injectors and their respective timing settings for each of the particular engine models for which an emission kit was designed, together with the four pass counterflow aftercoolers, have provided the ability to operate at reduced NOx levels without sacrificing engine performance or creating additional smoke, CO or particulate emissions. Development of these kits for engine modification was accomplished over an extended time period requiring many tests to determine the ideal injection timing for each engine model. The results of these tests then determined the proper injector construction features and the characteristics of the aftercoolers that form major features of the kits. 
   While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.