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The new technology was tested on a Caterpilllar heavy duty diesel engine. It achieved a thermal efficiency of 53 percent much better than the most efficient auto diesel engines (about 45 percent) and better even than the most efficient diesel engine in the world -- a turbocharged maritime engine that is 50 percent efficient.  (Source: Caterpillar Equipment)

The new engine could cut U.S. oil consumption by 4 million barrels a day -- roughly the amount that the U.S. imports from the volatile Persian Gulf.  (Source: Flickr)
New engine could get better gas mileage than mild hybrids even

Diesel and gasoline are both great fuels from a chemical standpoint, each with its own unique advantages.  Diesel burns more completely, lubricates the engine better, produces less carbon monoxide, and is safer as it does not produce as much flammable vapors.  However it has its disadvantages -- older engines can have a greater danger of incomplete combustion, overall engine power is a bit lower, and diesel engines weigh more.

Gasoline 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 flammable vapors.

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 conditions.

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.

Professor Reitz 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 easily."

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 efficiencies.



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RE: Very cool!
By FITCamaro on 8/4/2009 3:14:37 PM , Rating: 3
Imagine though if you could have the torque and mpg of a diesel, and the horsepower of a gasoline engine. I'm not sure if it can work that way though. Transition from one fuel to another as rpms rise.


RE: Very cool!
By Keeir on 8/4/2009 3:34:33 PM , Rating: 2
I think.... from reading the article, the Engine would essentially "revert" to Diesel like operation at low power demands. You would only get the mpg of a diesel (actually even better) at steady state operation. Accelerating would get you the power of gasoline, but at much closer to gasoline mpg. Torque would be up in the air... I think it could probably be tuned to give closer to an ideal torque-->power transition since essentially your burning the "ideal" mixture at any one time.


RE: Very cool!
By Johnmcl7 on 8/4/2009 3:52:52 PM , Rating: 2
You don't need the horsepower of the petrol engines, the diesels do just fine on their own - while on paper they may look slower due to being down on power and slower 0-60, their fast midrange acceleration makes up for it. The Skoda Fabia VRS has a 130bhp 1.9 TDI PD engine (VW), it was able to outpace its Mini Cooper rival on the racetrack due to its straightline speed and is faster than a BMW 330i 50-70 despite being slower 0-60.

Seat currently run diesel Leons in the WTCC (they run under the same rules as the petrols), they took the manufacturer's championship last year and look to do the same this year as the petrol powered BMW's have been unable to match the performance of the Leons. Rather oddly BMW have been complaining about the Seat diesel engines despite making some outstanding diesels for their roadcars at the moment.

Diesel performance in Le Mans hasn't been too shabby either, a petrol car hasn't won it for a while and even rules put in places to reduce performance of the diesel cars hasn't stopped them winning


RE: Very cool!
By FITCamaro on 8/4/2009 9:56:09 PM , Rating: 3
A diesel only revs to 5000 rpm tops. If the motor can transition from diesel to gas as rpms rise, then it can rev to 6-7000 rpm like a normal motor. Thus increasing the powerband of each gear.


RE: Very cool!
By mindless1 on 8/9/2009 6:45:35 PM , Rating: 2
0-60 is largely irrelevant for mass consumer automobiles, no sane person floors it from 0 to 60 out of need unless it's a very rare situation.

How odd it is that people are thinking performance, as if they fancy themselves race car drivers. That's the opposite of good fuel economy, self-defeating sillyness.


RE: Very cool!
By DeepBlue1975 on 8/5/2009 9:59:24 AM , Rating: 2
There are some european models that achieve this.
For example, BMW's 1 series Diesel version is the same size as its gas counterpart (2 liter) and features 177bhp versus 170bhp that the gas version has.
The mileage is much better on the diesel one as the torque figure is... The only disadvantage is that you get a slightly noisier engine (you'll only notice that when outside the car in practical situations), and that the diesel engine does not rev as high as the gas one (I don't consider this a disadvantage at all, rather a simple difference).

And also diesel cars usually outlive their gas counterparts, even though the maintenance costs are a bit higher (the oil changing intervals and other routine maintenance tasks do have shorter intervals than on gas versions).

I like diesel better than gas. More efficiency, less need to rev high to get a good performance (talking about high power diesel engines, and not older designs that only had great mileage but also really awful performance figures), and they don't sound nearly as crappy as they did some years ago.

Nevertheless I would think that from a pure cost-benefit standpoint, this new breed of "gasesel" engines isn't as promising as using pure diesel engines is.
For transitional purposes (I mean: transition towards alternative fuels), all electrics and gas/diesel electric hybrids look as a better path of development in the long run, at least IMO, and even though those technologies are priced on the steep side as of now.


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