Most current flex-fuel vehicles are capable of operating on gasoline/ethanol blends from E0 to E85. The presence of gasoline in the fuel enables cold startability because some of its more volatile components can still vaporize at cold temperatures and produce an ignitable mixture. However when E100 is used, other means are required for cold starting because of ethanol's relatively low vapor pressure at low temperatures. A common technique is to employ an auxiliary gasoline fuel system for use only when temperatures are too low for the vehicle to start on E100 alone. But the added cost, complexity and maintenance of such systems have driven the search for a simpler approach.
One such technique is to heat the fuel prior to injection. Fuel systems currently exist where heating occurs within the main conduit of the fuel rail. Another method is to heat the fuel within each fuel injector. A common misconception is that heating the fuel locally at the injector does not create a sufficient quantity of heated fuel capable starting and maintaining engine operation until the engine can run on unheated fuel.
This paper offers a summary of Delphi's development of a viable heated injector system. Along with injector design optimization techniques, vehicle test results showing improved cold start times and reduced emissions are presented. These efforts have helped produce an injector design and control strategies yielding improved ethanol cold start times compared with existing heated rail systems. Consequently, heated injector production is scheduled to begin during the second quarter of 2012.