THE MID-TERM OUTLOOK FOR AUTOMOTIVE FUELS AND ENGINES

Two powerplants which are capable of substantially improved fuel economy over the conventional spark ignition engine are the diesel engine, which offers 20%-60% fuel economy gain at somewhat reduced acceleration performance; and the direct-injected, stratified charge (DISC) engine (an improved spark ignition engine) of which the Ford PROCO (programmed combustion) engine is an example. The diesel engine's market penetration will depend on resolution of exhaust emission problems (particulates). The early version of the DISC engine also had unaccepatable emission characteristics. An added advantage of the DISC engine is its ability to accept a wide variation in fuel composition. Other types of powerplants under study are electric powered vehicles (depending mostly on improved battery design), gas turbine engines (high cost, poor fuel economy, and high emissions), and Rankine and Stirling cycle engines (not likely to be produced). Alcohols as fuel or as extenders for gasoline have the appeal of availability from domestic nonpetroleum sources. Gasohol (90% gasoline, 10% ethanol) is currently being marketed in limited quantities. Use of pure alcohol depends on the design of new engines with higher compression ratios and improved cold start performance. Larger fuel tanks will also be required. Cost and availability of alcohol are subject to future variation, but ethanol from fermentation of biomass will be much more expensive than gasoline and more costly than methanol from coal. The production of ethanol from grain absorbs more energy than the product furnishes; alcohol production from waste material would be more cost/effective. Phase separation is a serious problem with alcohol, especially methanol. Synfuels (liquid hydrocarbons from oil-shale and coal) are being considered as an essential part of the national energy plan. "Broadcut fuel," with a wide range of component boiling points, is a possible candidate, although it will require a new family of engines to accommodate its use.