If your vehicle is fuel injected, and is 1995 or newer, you will only need two things in order to convert your engine to flex fuel. You will need an electronic control module that plugs in between the fuel injectors and the factory fuel injector electrical connectors. There are a number of companies that manufacture these units and you can find them for purchase online without too much trouble. The other part needed which is an absolute must is a fuel sensor that detects the alcohol/gasoline ratio. This fuel sensor is connected to the electronic control module you just bought above, and is used by this module to determine how much fuel flow is needed based on how much ethanol or methanol is in your fuel. The higher the alcohol content, the higher the fuel flow needs to be.
Can there be problems? Yes – E85 and M85 are used in Europe, and since methanol is so clean when burning, it is important to have fresh O2 sensors and a very well-tuned up car. Ethanol and Methanol can affect seals in your fuel pump if they are rubber. Buna-N and Viton are synthetic rubber sealing materials used in many vehicle fuel pumps and works just fine with gasoline and alcohols. Buna-N seals are gasoline, methanol and ethanol proof and can be found on many US and foreign vehicles. Check with your mechanic.
Will a conversion kit void my manufacturer’s warranty? No – US Code – Title 15, Chapter 50, Sections 2301-2312. Legally, a vehicle manufacturer cannot void the warranty on a vehicle due to an aftermarket part unless they can prove that the aftermarket part caused or contributed to the failure in the vehicle (per the Magnuson Moss Warranty Act (15 U.S.C. 2302(C)).
The so called flexible fuel vehicle (FFV) runs on normal gasoline but also blends of gasoline and alcohol (ethanol or methanol). The limit in alcohol content is set to avoid cold starting problems during cold weather. Due to the lower energy density of alcohol compared to gasoline, the fuel economy is reduced in engines not specifically designed for alcohol use. However, the performance of the engine remains the same.
There are flexible fuel vehicles that adjust the fuel injection rate based on the oxygen sensor’s signal. The stoichiometric air/fuel mixture for gasoline is 14.7 whereas for E85 the required mass of air is 8.7 times the mass of the fuel to be burned in the cylinder and M85 due to its higher oxygen content only 6.5 times for methanol. If the alcohol content in the fuel increases the oxygen sensor will indicate a lean mixture and the ECM will adjust the amount of fuel injected. When using this method any change in the air/fuel ratio will result in an adjustment of the fuel injection, even though the change might be related to some failure in the system. Therefore, it is more accurate and reliable to employ a flex-fuel sensor. The sensor determines the alcohol type and content before it is injected. For an immediate response the location of the sensor is chosen as close to the injector as possible.
The picture above shows the measurement cell of the sensor. It is basically a cylindrical capacitor consisting of two tubes, the inner and outer electrode. The fuel flows through the gaps between. An AC voltage is applied to the electrodes. The relative permittivity of the fuel changes with the ethanol content, which leads to a change in the capacity accordingly (picture on the left). As the capacitance increases with increasing ethanol content, the oscillation frequency in the system will decrease and vice versa.
The analog frequency output is tied to a microprocessor which determines the capacitance by working backwards from the measured frequency. Due to the correlation between alcohol’s permittivity and the fluid’s temperature, the microprocessor corrects the capacitance for temperature variations in the fuel according to the output from an NTC (Negative Temperature Coefficient) thermistor. In addition, errors caused by the different conductivities of gasoline and methanol or ethanol are corrected.
The frequency of the single-wire output of the microprocessor to the ECM indicates the percentage of alcohol in the fuel. If required by the OEM the pulse width of the signal will indicate the fuel temperature. The ECM adjusts the injection according to the blend of the fuel, which leads to a more complete combustion.