Environment & Energy
In reply to the discussion: Mileage (mpg) Using Ethanol Seen 20% Higher Than EPA Says - Bloomberg [View all]leveymg
(36,418 posts)Last edited Fri Sep 20, 2013, 09:33 AM - Edit history (1)
while Indy series alcohol engines are limited to 1.5 bars. By comparison, modern high-performance diesels routinely pull 30 peak pounds (2.0 bar.) Part of the reason that diesels can pull more boost is that diesel fuel contains 11% more energy than gas and diesel engines generally favor torque production and have much longer strokes and heavier reciprocating components with resulting lower rpms (and horsepower potential) than a similar boosted gasoline engine. Alcohol by comparison has 33% less energy potential than gasoline, so I would think an an alcohol fueled engine that operates at 2 bars plus to compensate for the lower energy potential would be very highly stressed (and short-lived), indeed.
Gale Banks has a very informative article on diesel turbocharging and he goes into some of this, here: http://www.bankspower.com/techarticles/show/27-why-diesels-make-so-much-torque
On edit: While we're in a practical vein, here's an article in HotRod about a comparison of using E85 vs 104 Octane racing fuel. Indeed, it does allow one to bump the ignition curve and increase compression/boost levels, but it does come at a cost of a 25% loss in fuel milage compared to gasoline. Some older cars will need attention to fuel system components to run E85. Flame travel is slower with E85 so there may be a problem with detonation, but that can be managed by shaping the combustion chamber and piston tops to reduce hot spots. Otherwise, this article says the 85/15 alky/gas mix works remarkably well for high performance engines. http://www.hotrod.com/techarticles/hrdp_0801_e85_ethanol_alternative_fuel/viewall.html