Bi-fuel systems: natural gas for spark-ignition engines
When compressed natural gas (CNG) is burned, roughly 25 percent less carbon dioxide is released than with gasoline. CNG exhaust fumes are odourless and do not contain any particulate matter. In addition, the fuel does not require any additives, and its production does not involve any complex refining. Methane, the main component of natural gas, can also be produced in an eco-friendly way: either from biomass or using electricity generated from renewable sources such as the wind or sun. Although the network of CNG filling stations is growing all the time – CNG is available at some 1,000 filling stations in Germany – today’s vehicles are usually fitted with bi-fuel systems, so that they can run on both CNG and gasoline. Bosch supplies the entire injection system for bi-fuel operation. Known as NG-Motronic, it comprises the engine management system, the NG12 CNG injectors, fuel rails, and sensors for gas, tank pressure, low pressure, and temperature. Thanks to the strong antiknock qualities of CNG, natural gas engines can be further optimised. In conjunction with turbocharging, they can be downsized, thereby improving their efficiency and power.
FlexFuel technology: port fuel and direct injection systems for engines running on ethanol
In South America, plant-based ethanol is an important supplement to conventional gasoline. The fact that this fuel is made from renewable raw materials means it has a notable positive impact on carbon footprint. In the United States, more and more FlexFuel vehicles are being registered that can run on gasoline blends with up to 85 percent ethanol. Bosch developed the FlexFuel technology for these vehicles. The system allows spark-ignition engines to be run on varying mixtures of gasoline and ethanol – from gasoline to pure ethanol (E100). The engine control unit automatically adjusts injection, ignition, and other system parameters to the respective ethanol admixture and to operating conditions. FlexFuel systems are available for spark-ignition engines with both port fuel and direct injection. Because of its chemical properties, ethanol can adversely affect starting behaviour and engine running, especially at low temperatures. For this reason, Bosch has extended its range to include the Flex-Start system. If required, this system’s electrical heated rail preheats the fuel, thus allowing trouble-free starting and driving even when temperatures are low. As a result, vehicles equipped with this system no longer require a second fuel system solely for gasoline.
Bio-fuels in the diesel engine
Biogenic fuels can also be used in a diesel engine, where they improve this engine’s already very favourable carbon footprint: apart from bio-diesel, which already constitutes seven percent of the regular diesel available at filling stations, hydrogenated vegetable oils and second-generation bio-diesel can also be mixed with diesel. In this case, the admixture can be even higher than with conventional bio-diesel, yet without any need for adjustments to the injection system.