According to a recent WardsAuto.com article, when Toyota Motor Corp. introduced its 3.5L, DOHC V6, 2GR-FSE, many eyebrows were raised. The reason? The engine would be the first to combine direct-injection gasoline (DIG) fueling with conventional port fuel injection (PFI). The engine was launched in the 2006 Lexus IS 350, and has won two consecutive Ward’s 10 Best Engines awards.
Toyota indicated that the engine was developed in order to increase performance while at the same time reducing emissions. Now, others in the industry are “migrating to DIG fueling as a way to improve performance and fuel consumption” according to the article. Using direct injection alone forced Toyota to make certain compromises when developing engine technologies, for DIG used alone tends to limit volumetric efficiency and wide-open throttle engine performance. When combined with port fuel injection, an engine with DIG fueling would not experience curbed volumetric efficiency or high levels of cold-start emissions.
Toyota’s twin-injection design is called D-4S, a variation of the D-4 architecture which has been used since 1996 for four-cylinder engines and is now used in the inline 6 and V6 engine families. The D-4S delivers fuel in a “more evenly distributed spray pattern in the cylinder, precluding the need for high levels of charge motion,” according to the article. There is a DI injector and a port injector for each of the engine’s six cylinders. Toyota engineers say that brake-specific fuel consumption is improved by 4% and start-up emissions are reduced by 20%. The PFI system typically operates on its own during the actual cranking part of the engine startup phase. It is during this time that a substantial portion of the “raw” emissions of a cold start are produced. During high-load operation, only the DI injectors are used, which maximizes the DI’s ability to deliver a cooler and denser air/fuel mix. This promotes maximum power and torque.
As these types of technologies are further developed and improved upon, we should expect to see more of them in a wider range of vehicles, not just the premium brands. Automakers are continually finding ways to make more power and torque while at the same time creating engines that are more fuel efficient.Source: Visnic, Bill. (July 23, 2007). “Toyota V6 Twice-Injected With Innovative Thinking.” WardsAuto.com. Retrieved July 23, 2007 from www.wardsauto.com.