At the 2009 SAE World Congress, a Ford study revealed that a separate E85 direct injection boosting system combined with a petroleum port fuel injection makes an engine more efficient in its use of petroleum – and can be viewed as a more cost effective alternative to diesel.
The idea behind E85 boosting is that ethanol suppresses knock due to the large cooling effect it has on the air-fuel mixture when it is directly injected into the cylinder. The compression ratio can then be increased and the resulting higher BMEP levels mean the engine can be downsized at equivalent vehicle performance.
According to Robert Stein, the vehicle owner enjoys high fuel economy because the petrol, with its greater eating value per volume, is the fuel primarily used. Improved energy efficiency in turn leverages the effect of the limited supply of E85 compared to simply displacing petrol as with a flexible fuel vehicle.
The study saw the E85 boosting approach applied to two engines with the Ford team noting that the E85 DI and petrol PFI can be seen as an alternative to a modern diesel. There are several differences, however – the vehicle owner does not need to fill the E85 tank; and the engine is less expensive than modern high pressure diesel injection systems.
As a consequence, it is believed that the E85 DI and petrol PFI engine will cost significantly less than a diesel engine and be able to achieve more stringent emission standards reducing petrol consumption and the net CO2 emissions.
