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The accurate measurement of air volume is one of the critical issues in an LPL-EGR system, which has a large intake volume from the EGR valve to the combustion chamber compared to an HPL-EGR system. This includes the difficulty of measuring the flow rate of the LPL-EGR accurately. In this study, we investigated the EGR rate estimation logic with the cylinder pressure for an LPL-EGR system. This methodology is characterized by an EGR rate estimation, which uses the polytrophic change during the compression stroke, depending on the mixture and EGR rate. The polytrophic index is mainly changed by the EGR rate and the airflow rate. The EGR rate is estimated by the difference between measured pressure with sensors, and referenced pressure, which is calculated by measured parameters before compression with the assumption that the EGR rate is zero. To calculate the exact EGR rate, the influence of the air fuel ratio on the cylinder pressure was also taken into account.

Osaka University Formula Racing Club (OFRAC) [1] won the first prize in the 8th Student Formula SAE Competition of Japan [2] organized by the Society of Automotive Engineers of Japan (JSAE). The technical developments, especially on the power train system, acted very important roles for this winning. Three technical developments were introduced to meet the machine concept “Get more performance at corner exit.” They are; (1) Dry sump lubrication system to reduce the height of the center of gravity (C.G.), (2) Rotary throttle valve system to get more power and (3) Semi-automatic shift up assist system to reduce the loss of traction force during shifting up. In this paper, these unique technologies, which were originally student-developed, on the power train of our championship car, ‘OFRAC Naniwa-X,’ are focused [3].

A fuel supply system and characteristics of CVT (Continuously Variable Transmission) were changed to get better dynamic performance of an engine and axle output, respectively. A fuel supply system were changed from carburetor to fuel injection to improve an engine power. Engine power and torque with fuel injection system were higher than that with carburetor system by approximately 19% and 21%, respectively. In the power transmission system, the effect of spring constant of pressure spring and weight of flyweight on engagement speed and shift speed were investigated to improve an acceleration performance. Engagement speed and shift speed were higher as spring constant of pressure spring increases and weight of flyweight decreases, respectively.