Designing engines to exploit ethanol's important advantage over gasoline

In the January 20, 2009 post of Robert Rapier's R-Squared Energy Blog (one of my energy-blog favorites), Rapier makes a compelling case that ethanol-fueled engines need to be designed to exploit the much higher octane rating, thus greater efficiency of ethanol over gasoline. With its higher octane rating, ethanol does not easily pre-ignite. Thus, if an engine were designed with a much higher compression ratio to exploit this advantage, it is conceivable that cars could actually go further on a gallon of ethanol than on a gallon of gasoline, even though ethanol only has 2/3 the BTU's per gallon that gasoline has. This is an interesting observation from Rapier who has to remind people from time to time that he really isn't anti-ethanol in spite of some earlier posts. This particular post is well worth reading, as is Rapier's entire blogsite. The above picture is of a high-compression ethanol/biodiesel engine built by Swedish automaker Scania.