: KASTEC's System : LPG System Explanation : SYSTEM Characteristics : : System Diagram : Wiring Harness Connection Diagram : KASTEC's Bi-Fuel system is based on the gasoline EMS system, and is adapted to the only LPG specific components. Therefore LPG caburetor must be applicated, and electrical interfacing module is necessary to operate LPG components. And it is a kind of hybrid fuel system which has the best driveability in LPG fuel mode to be suitable to all driving conditions. For example, when you start the engine with just only LPG fuel in the every morning in winter, your vehicles may have the serious problems like as engine backfiring and worse startability than gasoline. But KASTEC's system is operated by gasoline at the beginning of start at the cold condition according to the signal of coolant temperature sensor against those problems forcibly,and when the engine reached the temperature to be suitable to be driven by LPG fuel,the fuels are alternated from gasoline to LPG by themselves. In this situation, there is no driver's operation to alternate fuels. This is one of the main characteristics of KASTEC's system. Besides, KASTEC's LPG(CNG) carburetor(Mixer) was designed to be the equivalent performance to the gasoline fuel mode at low engine speed condition, and to be the high stability at the engine idle condition, and to be minimized the TAR contamination of gasoline original components at the idle condition.   FCM(Fuel Control Module) detects the engine operating condition by the several input signals of RPM, throttle position, coolant temperature and oxygen density etc,. After determining the proper fuel to be used according to each engine conditions, it controls the actuator for LPG and gasoline fuel. And it controls LPG duty[%] solenoid valve for feed-back control which is mounted on LPG Carburetor(otherwise is called "LPG Mixer" or "Adaptor") for a constantly optimal air-fuel ratio. When engine is warmed-up, after calculating the input signal of oxygen sensor, FCM makes LPG duty[%] solenoid valve operated to be the stoichiometric air- fuel ratio which realizes the best conversion efficiency of the three-way catalytic converter. Normally the fuel control of open-loop means that the fuel supply is entirely dependent upon the one-sidely pre-determined value fixed in FCM or devices, which is not considering the value of input signals from each sensors. And it is classified into two kinds, one is to control engine when close-loop control is not available, the other is to control the whole engine operation condition by open-loop method unconditionally. When engine is cold, it starts by gasoline fuel, then operates until engine reaches the suitable temperature to be operated by LPG fuel. During the fuel alternating, FCM controls to be minimized the fluctuation of engine speed and Air/Fuel ratio by means of LPG density compensation program stored in FCM. And even if engine reaches the suitable temperature to be operated by LPG, until it is not warmed up fully, it operates by only open-loop method. This is for the reason that open-loop method makes engine normal faster than close-loop. At this time, the input signals of sensors are not considering. When engine has fully warmed up, basically engine operates by close-loop method. But also even if engine is warmed-up, when it needs higher or lower power than normal condition as like full-load condition and deceleration condition etc., it operates by the pre-determined value of open-loop method stored in FCM to increase or reduce engine power. This is for the reason that open-loop control is suitable for supplying engine with more or less fuel than close-loop control. Therefore the duty[%] values of open-loop control are depend on the pre-determined values stored in FCM at the specified engine condition, but when engine is operating in normal condition, the close-loop control is performed by the program stored in FCM. When engine has fully warmed up, it runs by the A/F control of close loop method according to the output signal of oxygen sensor, which is mounted on the exhaust manifold to detect oxygen density, at the normal driving condition. The oxygen sensor has the peculiar characteristics that its signal changes suddenly within a narrow zone, which is called "Window", of proximity to the stoichiometric air-fuel ratio, the catalytic converter is used to keep the gases CO, HC and NOx so little at the stoichiometric air-fuel ratio. To achieve this, the close-loop control is performed by the amount of duty[%] value of Feed-Back solenoid valve to prevent the oxygen density in exhaust gas from growing too great or too small. If the output voltage of oxygen sensor is over 0.45V, which is called "slice voltage" to be the criterion of "Lean and Rich", When FCM detects that the present A/F is rich, and keeps the duty[%] value of feed-back solenoid valve to be reduced until its output voltage is below 0.45V. Reversely when the output voltage of oxygen sensor is below 0.45volts, FCM keeps the duty[%] value of feed-back solenoid valve to be increased until its output voltage is over 0.45 volts. This process is done repeatedly to be toggled at nearby stoichiometric air-fuel ratio.   Normally the duty[%] solenoid valve is mounted on LPG carburetor(Mixer). The opening time of duty[%] solenoid valve is determined according to the valves of output signals of various engine management sensors by the program stored in FCM. Especially, for close-loop control, it is dependent upon the output signal of oxygen sensor and coolant temperature sensor, throttle position sensor.. By controlling air-fuel ratio at various driving condition, the conversion efficiency of three-way catalytic converter and vehicle driveability and fuel economy could be improved. The duty[%] solenoid valve operates with the frequency of 20Hz (50msec) in the method of "On/Off" operation element. When it is opened ("On"), the path of by-pass fuel is penetrated and the additional fuel is supplied to engine, reversely when it is closed ("Off"), the additional fuel is shut off. The fuel supply quantity of duty[%] solenoid valve is controlled by increasing or decreasing the length of time between the raising of the plunger and pulling down of it periodically. And the plunger of duty[%] solenoid valve operates in a period, is called "Cycle", and the duty[%] means the time ratio that it is open during a cycle. The large amount of duty[%] means that a lot of additional fuel is supplied to engine because of lean air-fuel ratio, reversely the small amount of it means that a little additional fuel is supplied to engine because of rich air-fuel ratio. ㆍAutomatic fuel selection according to ambient    temperature ㆍAutomatic fuel alternation without any driver's    operation ㆍEquivalent driveability to LPG dedicated vehicle ㆍDisplay LPG operating status by Lamp ㆍBoth fuel metering by 1-fuel meter in    instrument panel ㆍEasy and safe 2 level On/Off switch ㆍLPG density correction when fuel alternating ㆍVarious LPG fuel control algorithm equal to    LPG only dedicated vehicle ㆍSuitable to emission regulation test (LA-4)    condition ㆍEquivalent performance to gasoline at low    speed ㆍHigh idle stability equivalent to LPG dedicated    vehicle ㆍNo backfiring when engine starting ㆍNo failure of injectors and fuel pump by    occasional gasoline operation ㆍAvoiding the failure of Idle Air Control Valve for    gasoline ㆍNo engine dieseling when engine stopping ㆍAutomatic emergency LPG fuel cut-off ㆍCost reduction by using a LPG fuel cut-off    solenoid valve ㆍCommon use of system sensors for gasoline    fuel ㆍLow price LPG components ㆍEasy work       ㆍLPG Feed-Back Control ㆍLPG Density Compensation Control ㆍLPG Supply Display Control ㆍFuel Metering Control ㆍLPG Emergency Cut-off Control ㆍMixed Dual Fuel Control ㆍEngine Cold Condition Control ㆍIdle Close-Loop Control ㆍDecel Fuel Cut-off ㆍAccel Power Compensation Control ㆍSelf Diagnosis