Development of internal combustion engine control system is currently oriented on exhaust emissions, performance and fuel efficiency. This is caused by fuel prices rising which led to a crisis on the transport sector; therefore it is crucial to develop a fuel-efficient vehicles technology. Gasoline engine fuel efficiency can be improved by several methods such as by controlling the air-to-fuel ratio (AFR). AFR technology currently still has many problems due to its difficulty setting characteristic since AFR control is usually as internally engine control. Fuel efficiency can be improved by influence of external engine system. Brake control system is an external engine system that used in this research. The purpose of this research is to design and implement the AFR and brake control system in a vehicle to improve fuel efficiency of gasoline engines along braking period. The basic idea is the controller has to reduce the consumption of fuel injection along braking period. The applied control system on vehicle works using smart controller, such as Fuzzy Logic Controller (FLC). When the vehicle brakes, fuel injection is controlled by the ECU brake control system. This control system works in parallel with the vehicle control system default. The results show, when the engine speed exceeds 2500 rpm, AFR value increased infinitely, so that maximum efficiency is achieved. At engine speed less than 2500 rpm, AFR value reaches a value of 22. The fuel measurement has been able to show a decrease in fuel consumption of 6 liters to 4 liters within the distance of 50.7 km. Improvement of fuel efficiency can be achieved by approximately of 33.3%.

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Abstract-Due to the needs of improving fuel economy and reducing emissions, it is increasingly important to achieve control over robustness behavior and meet performance objectives over the life of the vehicle. This requires the development of high performance and optimal power train controllers. The performance objectives are often conflicting, or at least interrelated. One way to potentially meet these performance requirements is to introduce a method of controlling engine torque of Spark Ignition (SI) engine using Linear Quadratic Integral Tracking (LQIT) optimal control. The goal is to develop simple algorithms which can control engine torque well, thus providing fuel control more efficient and simultaneously improving engine performance due to the needs of the driver based on throttle opening information. In this case, spark ignition engine with automatic transmission simulation model is used to meet a good performance under this controller design. Keywords-engine torque, LQIT optimal control, SI engineAbstrak-Berkenaan dengan adanya regulasi dan kebijakan pemerintah terkait dengan ketentuan teknologi otomotif yang hemat energi dan ramah lingkungan, maka pengembangan teknologi kontrol untuk memperbaiki waktu transien pada mesin kendaraan dengan menjaga kinerjanya tetap baik, menjadi permasalahan sangat penting. Untuk dua pekerjaan ini diperlukan pengembangan teknologi kontroler dengan kinerja tinggi dan optimal. Hal ini dikarenakan upaya untuk melakukan penghematan energi/bahan bakar dan menjaga kinerja mesin otomotif tetap baik merupakan upaya yang saling bertentangan atau paling tidak saling melemahkan. Salah satu metode kontrol yang secara potensial bisa dimanfaatkan untuk permasalahan ini adalah dengan melakukan pengaturan engine torque pada Spark Ignition (SI) engine dengan menggunakan Linear Quadratic Integral Tracking (LQIT) optimal control. Tujuan dari penelitian ini adalah membuat suatu algoritma kontrol torsi mesin sederhana yang dapat digunakan untuk penghematan penggunaan bahan bakar dan juga sekaligus menjaga kinerja dari mesin sesuai dengan informasi bukaan pedal gas yang diberikan pengemudi. Pada kasus penelitian ini akan digunakan model simulasi spark ignition engine dengan automatic transmission untuk menghasilkan pembangkitan torsi sesuai dengan metode kontrol tersebut.Kata Kunci-torsi mesin, kontrol optimal LQIT, SI mesin

At the time of deceleration, continuous LPG flow in LPG fuelled engine causing over fuel consumption and increasing exhaust emissions, while the engine does not need fuel. Therefore, this paper presents a simulation of deceleration fuel cut-off (DFCO) system. Given that the fuel system control is complex and non-linear, modeling with fuzzy logic controller (FLC) has been selected because of simple, easy to understand and tolerant to improper data. The engine modeling is divided into several sections, including intake manifold dynamics and engine dynamics. The input values were processed by the membership function. A series of simulation results indicate that DFCO can be applied. The combination of throttle valve position, engine speed and manifold pressure is able to cut LPG flow at deceleration. As a conclusion, DFCO system is promising to be applied on LPG-fuelled vehicles for saving fuel and reducing emissions.