As highlighted previously in this blog, the Department of Energy (DOE) is supporting engine and vehicle research to investigate the potential of high-octane fuels to improve fuel economy. Given that ethanol has very high research octane number (RON), the alternative fuel makes an excellent spark ignition engine fuel, scientists say.
Even more research is emerging, showing that the prospects of increasing both the ethanol content and the octane number of the gasoline pool has the strong potential to enable improved fuel economy in future vehicles with engines that will be downsized and capable of maintaining cruising speeds with reduced revolutions per minute (RPM).
The latest report, which is from experts at the DOE’s Oak Ridge National Laboratory (ORNL), describes a study that explores the potential performance benefits of high-octane ethanol blends in the legacy fleet of nearly 18 million flex-fuel vehicles (FFVs) that are on U.S. roads today, all capable of using any fuel ‑ from straight gasoline with no ethanol blended, to a blend of 85 percent ethanol (E85).
The researchers say that if a future high-octane blend for dedicated vehicles is on the horizon, the nation is faced with the classic chicken-and-egg dilemma – can a market be built for FFVs if there are no high ethanol blend fuels available, or why produce higher-blend fuels if there are no FFVs to use it. However, the ORNL team says, if today’s FFVs can see a performance advantage with a high octane ethanol blend such as E25 or E30, then perhaps consumer demand for this fuel can serve as a bridge to future dedicated vehicles.
Experiments were performed with four FFVs using E10 with 92.4 RON (an 88 pump octane) and an E30 fuel with a 100.7 RON (a 94 pump octane). Two of the vehicles had gasoline direct injected (GDI) engines, and two featured port fuel injection (PFI). Significant wide open throttle (WOT) performance improvements were measured for three of the four FFVs, with one vehicle showing no change.
Additionally, a conventional (non-FFV) vehicle with a small turbocharged direct-injected engine was tested with a regular grade of gasoline with no ethanol (E0) and a splash blend of the same fuel with 15 percent ethanol by volume (E15). RON was increased with the ethanol blend, from 90.7 for the E0 to 97.8 for the E15. Significant wide open throttle and thermal efficiency performance improvement was measured for the vehicle, which achieved near volumetric fuel economy parity when tested under high-speed, aggressive driving conditions, demonstrating the potential for improved fuel economy with high-octane fuels in the smaller, RPM-reduced engines expected to come.
Currently, ethanol use in FFVs is nowhere near the available capacity, a shortfall often attributed to limited E85 infrastructure. However, if a new high-octane mid-level ethanol blend for future vehicles is on the horizon, it could be beneficial to begin building out this fueling infrastructure now. Many Flex Fuel blender pumps offer a range of fuels today, often including E30. Marketing a fuel such as high-octane E30 as what the DOE scientists call a “Renewable Super Premium for your FFV” could increase demand and help grow the infrastructure, provided the fuel is priced and marketed effectively.
The research team notes that EPA’s Tier 3 rule, which sets new vehicle emissions standards beginning in 2017, does contain language that allows manufacturers to request approval for an alternative certification fuel such as a high-octane E30. However, before vehicles requiring this fuel can be offered for sale, the fuel needs to be widely available ‑ much like unleaded gasoline was available in 1975 before vehicles requiring it were sold. Given that nearly 18 million FFVs on the road today can legally use such a fuel, consumers will need some incentive to purchase the fuel.
Three of the four tested FFVs showed performance improvement with high-octane E30 compared to regular E10, indicating that marketing E25 or E30 to FFV owners as a performance fuel may enable greater ethanol utilization in the near term, the scientists say. That could then help encourage the installation of additional refueling infrastructure – pumps, storage tanks ‑ to enable manufacturers to build dedicated vehicles designed for a high-octane midlevel ethanol blend.
The growing research continues to underscore the need by regulators to adopt policies that encourage the production of these high-octane ethanol blends as well as flex-fuel vehicles. Given that a significantly attractive prospect of such fuels is that they can be used legally in nearly 18 million FFVs on the road today, the current FFV fleet can serve as a bridge by providing a near-term market for the fuel, making it widely available and enable future vehicles optimized for the new high-octane fuel to realize improved efficiency. The end result will be improvements in fuel efficiency and vehicle performance. And what’s not to like about that.