Optimization Design Of Reducing Fuel Consumption For 4G6 Engine

Higher requirements for the development of technology of finished automobiles and engines have been put forward as the national laws and regulations of fuel consumption and exhaust are becoming stringent increasingly. Part of the old types of engine without WT and S-CHG and other new technologies are facing the risks to be wiped out from the market. Some automobiles mounted with 4G6 type engine have not met the needs of the limited fuel consumption value of the second stage since the national standard GB19578-2004-the Limited Fuel Consumption Value for Passenger Automobiles was published, and this is the very background for us to improve the 4G6 type engine.Optimized design to 4G6 engine have been made as following in order that the cars with this type of engine can satisfy the demands of the second stage in the national standard GB 19578-2004 and extend its life circle in the market, promoting its dynamic and lowering its fuel consumption.1. Improving the compression ratio of 4G6 engineThe compression ratio of 4G6 engine has been increased to 10 from the 9.5 via the redesigned piston with changing its pit form into plain head. High compression ratio can perfect the burning, improve the cycle thermal efficiency and hence increase the dynamic of the engine and reduce the fuel consumption.2. Anodized process to the top and ring land of the pistonThe higher compression ratio may increase the piston's thermal load. In order to decrease the damage to piston caused by thermal load, anodized process has been applied to the top and ring land of the piston, increasing the piston's capability to resist the thermal stress.3. Adding solution heat treatment in the process of piston heat treatingThe increased compression ratio will also increase the exploded gas pressure in the cylinder that piston should bear. Addition of solution heat treatment into the piston heat treating process may improve hardness, tensile strength and elongation of the piston, increasing its capability of mechanical load.4. A V groove made in the second ring land of the piston The special technology of making a V type groove in the second ring land of piston, introduced from Mitsubishi, Japan, can reduce the grease wear of the engine.5. Graphite coatings sprayed on the skirt of the pistonThe graphite coatings on the skirt of the piston can lower the friction loss, enhance the mechanical efficiency, boost the dynamic of piston and decrease the fuel consumption.6. Lowering tension of the piston ring groupsThe functions of each piston ring have been detailed analyzed in this paper, and target values of tension of each piston rings have been determined according to the experience diagram, and decrease the tension value of piston ring group by 25%, lowering the friction loss of the engine.7. Reasonable design for the height of each ringThe heights of the second ring and the oil ring have shortened except for that of the first one, resulting in light weight of piston, reduction of friction, decrease of forms of HC and improvement of anti-flutter.8. Reasonable design for surface pressure of the pistonTo keep surface pressure of the oil ring the not changing and maintain its shaving oil ability as far as possible, the surface pressure of the fist ring may be adequately increased to improve the sealing effect, and that of the second ring will be determined by its designed values of tension and ring height.9. Verifying the follow-up coefficient to guarantee the shaving oil ability of the nngThe radial thicknesses of the piston rings have been redesigned to increase the follow-up coefficient k, it is verified that the coefficients k of the first ring and the oil ring have been increased with that of the second ring slightly decreased, and it is found that the follow-up coefficient of the second ring can meet the need of application in accordance with the experience diagram from Mitsubishi.10. Dynamometer verifyingFirstly, the engines are recalibrated on the test bed to get new ECU data, then the actual effects of every optimized designs are verified by the original engine compared with the improved one, including tests of external features, universal characteristics and fuel consumptions, etc. the tested results are well as excellent as what have been expected. And the life test of the improved engine has been made; the newly designed parts totally passed the test.11. Finished automobile test verifyingThe improved engine is mounted with a finished car and is calibrated optimized to collect the final data, and then the fuel consumption is determined by the work test machine of wheel hub. The results shown prove that the fuel consumption of the automobile with improved 4G6 engine fully meets the demand of the second stage described in the national standard GB19578-2004-the Limited Fuel Consumption Value for Passenger Automobiles.The conclusion comes below when the project is finished:1. Increase of the compression ratio of the engine can improve the combustion and promote dynamic and economy of the engine, but it can also cause some negative influence, for example, the higher thermal load and mechanical load of the parts may bring about knocking and surface ignition. These factors restrict the higher compression ratio and other better measures should be worked out to eliminate the negative sides.2. The reformed plain head can reduce the thermal load and mechanical load of the piston.3. The anodized process and solution thermal process to the piston can effectively improve piston's resistance against thermal load and higher mechanical load.4. The V groove opened on the second ring land can be good for lowering fuel consumption.5. The coatings on the piston skirt can improve the dynamic and economy of engine, to avoid extra abrasion and prolong the life cycle of the motor.6. Fuel can be saved if tension of piston ring group is lowered, but the grease wear in engine may rise because too low tension may decrease the function of the ring.7. Detailed analysis of designs of tension, surface and ring height has been made based on the functions of each ring. The first ring may ensure the gas sealing; its surface pressure and tension should be higher enough without causing extra friction loss. The second ring lower the minimum tension, so that the improvement of second ring decides the friction loss. And the surface pressure of oil ring should keep stable or slight decrease, and the follow-up coefficient k must be verified after the final designs of each piston rings.