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Flexible fuel vehicles have been a challenge for the automotive industry due to the chemical properties of ethanol combustion. Especially on days in which the ambient temperature is below 18 degree Celsius, flexible fuel starting is critical due to high ethanol flash point. To solve this problem, cold start systems have been implemented in flexible fuel vehicles. Cold start systems that inject gasoline to assist in starting have been widely used. However, they dramatically increase the level of pollutant emissions during the cold start phase and they depend on the driver interactivity to refill the system with gasoline. Cold start systems using electric pre-heating have been recently launched into the automotive industry.

Air cleaners are used in a wide range of automotive applications. From passenger cars to heavy duty trucks, there is always an air cleaner to keep inlet air free of impurities and air flow passage obstruction in low levels. Today's automotive air intake systems are developed to deliver maximum filtration efficiency, maximum dust holding capacity and maximum service interval range based on engine performance and reliability requirements [1]. In Brazil, some applications require outstanding performance for the air cleaners. One of them is at harvester application. In this case, vehicles are exposed to thin soil particles in high quantities due to harvester movement at plantation work. At the same time, engine performance needs to be kept during long journeys. According to this limitation, re-fuelling and components replacements are done direct at field. Any vehicle stop means lower productivity and more costs.

Water separation from diesel fuel is a critical requirement for modern diesel engines. The main reasons are: corrosion, wear on the fuel system, irregular combustion and acceleration of microbiological growth that clogs filters, pumps and prefilters. Due to this, agencies regulate water content in diesel (like DIN EN590 [1]) and biodiesel (like DIN EN14214 [2]). Also international institutes release standards to define the correct procedures, equipment and boundary conditions to confirm water separation filter efficiency (like ISO 4020 [3] and ISO/TS 16332 [4]). If you consider the Brazilian diesel conditions and fuel system configurations, the existing specifications, procedures and boundary conditions don't represent actual field conditions. The key differences are water droplet size, flow rate, temperature, biodiesel content and fuel aging effects which all impact the water separation properties.

The flex-fuel engine technology evolution and bio fuels increasingly market presence brings new challenges on components development requirements. One of the affected products is the fuel filter, where downsizing, dust holding capacity and filtration efficiency are the improvement goals. In order to attend these market demands, MAHLE has developed a new flex-fuel filter generation. This new product is able to double the dust holding capacity while maintaining the filtration efficiency. In addition, new product dimensions, like body diameter and distance between inlet and outlet, are the same found in current solutions. In this way, it can be used in many vehicles with none or few modifications at interface components. First optimization was done through changes in filter housing design and fuel system line connectors. Second optimization was single layer cellulose media improvement to multilayer concept.

At flex fuel technology introduction in the Brazilian market, new technical issues came-up due to ethanol chemical reaction with component materials developed only for gasoline aging. One of these items was the gel formation at fuel system. This gel flows through the fuel systems and clogs the fuel filters. And, as final result, the fuel pump is lost due to overpressure working condition. To implement solutions against this way of failure, it was necessary to understand gel formation mechanism in laboratory level. In this investigation, many boundary conditions were changed and analyzed in order to identify contribution of each factor during gel formation process. As result, it was possible to implement a laboratory gel formation test for fuel filters, not depending any more from field tests and allowing test repeatability to develop an improved fuel filter.