Flex fuel vehicles from Bosch have an injection system which can be operated with gasoline, with any mixture ratio of gasoline and ethanol or with pure ethanol. Regardless of the supply situation concerned, end customers are flexible when it comes to the choice of fuel and are able to respond to any price developments immediately.
Ethanol as a fuel
Derived from plants, ethanol is an alcohol that can be used as a fuel. Ethanol is added to the gasoline, the ethanol proportion can be between 5 and 85 %. E100 is a fuel with 93 % ethanol and 7 % water, with no gasoline admixture.
The combustion basis of flex fuel and Flexstart systems forms the tried and proven port fuel injection technology. The networked system components precisely detect the ethanol proportion at all times. The control unit adjusts the air/fuel ratio accordingly, in order to transmit the requested torque cleanly and economically. Thanks to continuous further development, Bosch offers systems for direct injection too.
Flex fuel und Flexstart systems
Because ethanol is difficult to ignite at temperatures below 13 °C, vehicles with the flex fuel system have a small auxiliary fuel tank onboard. On the basis of sensor data, the control unit automatically switches to gasoline drive to guarantee a reliable and convenient start. After a short heat-up phase, the system reverts to ethanol drive.
Moreover, Bosch has expanded its range by the innovative Flexstart system. It heats up - where necessary – the fuel via electronically-controlled heating elements in the fuel rail, which, thereby permitting a smooth start and drive even at low temperatures. Consequently, the second fuel system and the auxiliary tank for pure gasoline are not required in these vehicles, and start comfort on cold days can be optimized.
Flex fuel with direct injection
Through consistent further development, Bosch also permits flex fuel systems to be used in combination with direct injection. Flex fuel systems with direct injection (such as flex fuel and Flexstart based on intake manifold fuel injection) use a mixture of ethanol and gasoline as a fuel. Engines with direct injection generate the air/fuel mixture in the combustion chamber itself. The fuel is injected directly into the combustion chamber via high-pressure injection valves.
The flex fuel system with direct injection offers additional advantages over flex fuel systems with port fuel injection. Air and fuel are precisely metered, prepared and distributed for each combustion cycle. The result: reduced consumption and lower emissions with higher engine output.