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Experimental diesel/gas engine could give 2009 Saturn a big boost in fuel efficiency

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July 18, 2014

Prof. Rolf Reitz (center) and members of his student team with the RCCI-powered Saturn

Prof. Rolf Reitz (center) and members of his student team with the RCCI-powered Saturn

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Five years ago we first heard about a Caterpillar diesel engine located at the University of Wisconsin-Madison, that had been modified to run on an unlikely-sounding mixture of diesel and gasoline. Not only did the one-cylinder engine work, but it was more efficient than pure-diesel or pure-gas engines at converting the chemical energy of fuel into motion. Sitting in a basement lab, however, isn't the same as experiencing use in the real world. That's why students at UW-Madison, led by Prof. Rolf Reitz, have now put another diesel/gas engine into a 2009 Saturn.

The original Cat engine utilizes a system known as reactivity controlled compression ignition, or RCCI. It uses sensors and a computer system to continuously and instantaneously adjust the ratio of the two fuel types. Diesel is injected to start the engine, as it has a lower ignition temperature than gas. From there, the fuel blend varies depending on real-time operating conditions, with the goal of "exploiting each fuel’s strong points."

As a result, the lab-based engine currently has an efficiency of 59.5 percent – regular diesel truck engines manage no more than 52 percent, and the theoretical maximum is 64 percent.

Assistant professor Sage Kokjohn (left) and Rolf Reitz with the original Cat engine
Assistant professor Sage Kokjohn (left) and Rolf Reitz with the original Cat engine

The engine's high efficiency is due largely to the fact that it runs much cooler than a pure gas or diesel engine, so less heat is wasted by being absorbed into the engine block or radiator. That lower operating temperature also allows it to run cleaner, minimizing its production of soot and noxious nitrogen oxides. Additionally, the injected diesel doesn't need to be pressurized nearly as high as it does in a conventional diesel engine, thus saving costs and lessening complexity.

The new RCCI engine replaces the existing combustion engine in a 2009 Saturn Aura hybrid sedan, and runs on conventional gasoline and diesel fuel.

"The engine has a lot of controls, so when you put your foot on the gas, we automatically change the amount of diesel and gasoline to optimize the combustion process," said Reitz. "We can blend the correct dosage on a cycle-by-cycle basis."

Road tests have just begun, so we look forward to hearing about how it performs and what sort of mileage it gets.

Source: University of Wisconsin-Madison

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
12 Comments

Great idea and it works. What about duel fuel with gasoline and CNG? You can fill up at home to run on CNG plus go with regular gas when there's no place to fill up.

Rehab
19th July, 2014 @ 08:52 am PDT

Just make sure you don't put gas in the diesel tank.

Slowburn
20th July, 2014 @ 02:29 am PDT

Slowburn - IT WOULD NOT MATTER! IT ADJUSTS!

That is the point ... If there is even a little diesel left, the fuel ratio computer can cope.

The Skud
20th July, 2014 @ 08:56 pm PDT

@ The Skud

Not if it needs more diesel than is in the mix in the diesel tank.

Slowburn
21st July, 2014 @ 03:18 am PDT

@ The Skud

I suspect that it only adjusts pure diesel with pure gasoline. Once mixed it is like a bell. It cannot be unrung and the fuel cannot be unmixed. Slowburn is quite right, filling up at a gas station will be a nightmare. Surely the time has come for it to be impossible to put the wrong nozzle in the wrong filler pipe.

Seeing as it does not need the injection pressure to be as high as a normal diesel engine, I wonder if a feature of the design is delayed induction valve closure, thus maintaining a 'low' compression ratio compared to that of the expansion ratio. Then, of course, we have a problem in determining what metric to use for the capacity of the engine: effective compression swept volume, expansion swept volume or combustion chamber volume.

Mel Tisdale
21st July, 2014 @ 03:29 am PDT

Once again, a joke by what once was the greatest car-producing country on the planet. Cars, then planes, then rockets, now look at us...

Let's tinker around some more with fuel combustion engines and "Increasing mileage"...lol

Hyundai has a car running on water. And this is the best Saturn can do? Quit being bought and paid for by the oil companies and actually make a car worth a darn.

Chris Culpepper
21st July, 2014 @ 09:06 am PDT

Its brilliant and,as oil prices fall over the next 5 years, this will be both a good alternative to and a good range extender for battery powered cars and trucks. Insofar as cars running water (or any cracked water function, such as hydrogen) there is already a massive shortage of municipal and irrigation water - pretty soon it will cost more than gasoline. Economics and common sense (in terms of acceptable emissions coupled with existing infrastructure and jobs) will still play a big part in determining what products consumers will purchase. $125,000 USD for a Tesla that's no better than a fully loaded $32,000 Kia Optima is a hard pill to swallow unless your pocket book belongs to the 1% for whom its merely a third car.

Mirmillion
21st July, 2014 @ 09:58 am PDT

I do not know enough to dispute the idea of mixing & managing fuels on the run. But I do know that such a complex system has enough sensors and controls to be a giant pain in the ass to fix as it ages. An idea that works great, or seems to, as a labtoy is not necessarily going to ever work out well as a product. Think of all the products, (not just cars), that have a great reputation and one of the key features will be simplicity. I would much rather read about developments such as new battery technologies that displace fossil fuels and do so elegantly.

StWils
21st July, 2014 @ 10:36 am PDT

Who is going to manufacture the final version ? Is it going to be GM - a big no-no or Caterpillar ?

None are suitable candidates for mass production. First for quality and the latter for volumes.

pmshah
21st July, 2014 @ 09:27 pm PDT

@ pmshah

A lot of trucks are powered by Cat engines.

Slowburn
22nd July, 2014 @ 07:02 am PDT

@ The Skud yes it should work automatically. I cannot vouch for this setup but it should work on the lines as my Scania Truck that ran on a combination of Diesel LPG (propane). The governing factors were the load imposed on the engine by the gross weight of the Truck, the road conditions (hill,flat,downhill etc) and the drivers right foot or cruise control.

The computer worked it all out so the driver would just drive. The only option was to turn off the LPG with a simple switch on the dash

The idea behind it all was to save diesel fuel. The principle was that the Diesel Pentane rating would only produce a certain "bang for the buck" so to speak. The LPG would "up the rating" and add horsepower by up to 40% depending on the settings made at the time of installation and the intended use of the Truck. My Truck was factory rated at 420hp and was set to produce 520hp with the LPG system. It worked best when pulling heavy loads and going up long hills. The fuel savings were tremendous and achieved by basically creating extra horsepower when needed and using less (expensive) diesel which was substituted by a low percentage of (cheaper) LPG. During idle and the initial low revs the gas was automatically off but once the revs came in the gas would be on and went off again momentarily between gear changes (it was auto box transmission).

Pulling lighter loads over long distances it also had great advantages by not changing down on long hills especially when there were no other vehicles getting in the way (night trunking on freeways).

I also "raised the bar" on this quest to save fuel by pulling a gooseneck lowrider trailer which brought the top of the container to the same height of the cab therefore reducing wind resistance. I also had a few months running on rapeseed oil instead of diesel which again saved on the overall cost of fuel but the smell of the rapeseed oil in traffic was unbearable especially in the summer as it would smell like a rancid chip fryer.............this resulted in a smoke stack exhaust being fitted which cured the problem.

Overall I was saving around 35% in fuel costs. The drawback was not just the cost of the system but also the cost of the lowrider trailer and the need to keep the truck on the road as much as legally possible.

In the end, the constant night shifts and the time away from home killed off the project..............but yes it worked very well.

bf_308
22nd July, 2014 @ 11:19 am PDT

What needs to be done is build a diesel engine that will run injecting methane instead of diesel.

Slowburn
25th July, 2014 @ 12:30 am PDT
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