on the other hand burns faster and produces more power (due to the
faster burn, not the energetic content). However, it also
typically yields worse gas mileage than diesel, combusts less
completely (in well-maintained engines), usually
requires a spark to ignite, and produces more pollutants and
Researchers at the University of
Wisconsin-Madison, led by Professor Rolf Reitz have come up with an
innovative solution -- an engine which blends
diesel and gasoline fuels to get the best of both worlds.
They have designed an engine which they say will be 20 percent more
efficient than traditional gas engines, while also lowering the
emissions. The new engine works via a technique called
"fast-response fuel blending", which means that the engine
mixes the diesel and gas to the perfect ratio for the current
Heavy loads (like that of commercial trucks) would
warrant a 85 percent gasoline to 15 percent diesel mix, while light
loads would typically induce a roughly 50-50 mix. Normally the
gas wouldn't combust in a diesel engine, but by adding just the right
amount of diesel fuel, combustion is achieved. In fact, the
special mix lowers engine temperatures by as much as 40 percent
drastically reducing the amount of energy lost to waste heat.
This allows the diesel engine to use cheaper low-pressure injection
(typically in gas engines only), and burns the fuel more cleanly,
producing less pollutants.
The researchers estimate that if
all cars and trucks in the nation adopted the new engine, it would
cut U.S. oil consumption by a third -- by 4 million barrels per day.
States Professor Reitz, "That's roughly the amount that we
import from the Persian Gulf."
The engine was developed
using theoretical models, then built using a Caterpillar heavy-duty
diesel engine as a base. The new engine achieved 53 percent
thermal efficiency, an admirable result, considering the best diesel
engine -- a massive turbocharged two-stroke used in the maritime
shipping industry -- gets 50 percent.
concludes, "For a small engine to even approach these massive
engine efficiencies is remarkable. Even more striking, the
blending strategy could also be applied to automotive gasoline
engines, which usually average a much lower 25 percent thermal
efficiency. Here, the potential for fuel economy improvement would
even be larger than in diesel truck engines. What's more
important than fuel efficiency, especially for the trucking industry,
is that we are meeting the EPA's 2010 emissions regulations quite
The one major downside is that the engine
necessitates a second tank. However, in order to meet EPA
nitrous oxide emission regulations the only alternative for large
diesel vehicles would be urea injection -- which would likely be more
expensive, less efficient, and still require a second tank.
While there's no telling how soon the engine will start popping up in
cars and trucks, it appears to be the best solution yet and the best
alternative to mild hybrids. Of course it could be combined
with hybrid electric technologies for even great fuel
quote: But then all you're really doing in the end is lowering your power output as you drop the octane rating.