MIT engine boosts mileage by 30 percent

Researchers at MIT say they can boost mileage in cars by as much as 30 percent, depending on the car, by a carefully planned injection of ethanol in the cylinder.

The engine, which is only about half the size of a conventional gas engine, could be on the market in about five years and could add about $1,000 to the cost of a car. That's less than the $3,000 to $5,000 added by a hybrid engine. Thus, consumers will recover the cost more quickly (because the engine uses less gas) and get about the same mileage as a hybrid.

If all of today's engines had the technology, MIT estimates, it could cut U.S. auto fuel consumption from 140 billion gallons to 110 billion gallons annually.

The ethanol injection suppresses the spontaneous combustion inside the cylinder. Spontaneous combustion creates an aggravating knocking sound, but with the knock eliminated, engine manufacturers can then adopt two design conventions common in diesel engines. With one, the engine can be highly turbocharged, which means that more air and fuel can be squeezed into the chamber.

Also, the engine can be designed with a higher compression ratio (the ratio between the compression chamber before and after compression). This allows the gas to expand more, releasing more energy.

With more gas working more efficiently in the chamber, mileage goes up about 30 percent. Leslie Bromberg and Daniel Cohn, at MIT's Plasma Science and Fusion Center, and John Heywood, director of the Sloan Automotive Lab and professor of mechanical engineering, have run simulations, and Ford is testing the concept with Ethanol Boosting Systems, the company formed by the three.

Gasoline and the ethanol would be kept in separate tanks.

"To actually affect oil consumption, we need to have people want to buy our engine, so our work also emphasizes keeping down the added cost and minimizing any inconvenience to the driver," said Cohn in a prepared statement.

[bigduke]

Alcohol boosted engine

The article mentions simulations. Has even a single cylinder engine been tested?

Fifty years ago I visited MIT Sloan lab and saw test engines on test. Is everything now in the silicon CPU and not real measurements?

My take is that a small true diesel and hybrid might be a better path. The motor would provide fast energy to drive train, and the engine would power steady state requirements. Add to that the energy recovery of braking dynamically.

[robmx]

30% More

And nothing says you couldn't make this engine one element in a hybrid. The story suggest that this engine matches a hybrids 30% savings. If this were one element in a hybrid does that mean we save 60%?

And the story says that this engine is half the size of a regular engine. Does this imply half the weight? If so is that fact and the added weight savings in the infrastructure of the entire car been taken into account in figuring the 30% savings and if not how much more savings would we save at this much reduced overall weight? Are we now up to 75%?

Only 25% to go. What we need is a small six pound fusion engine.

[robmx]

30% More

And nothing says you couldn't make this engine one element in a hybrid. The story suggest that this engine matches a hybrids 30% savings. If this were one element in a hybrid does that mean we save 60%?

And the story says that this engine is half the size of a regular engine. Does this imply half the weight? If so is that fact and the added weight savings in the infrastructure of the entire car been taken into account in figuring the 30% savings and if not how much more savings would we save at this much reduced overall weight? Are we now up to 75%?

Only 25% to go. What we need is a small six pound fusion engine.

[sugarfrosted]

A gas-powered diesel?

Hi, guys,

Based on the article, here's a viable alterative view of how they may have achieved their results:

It sounds like they've designed a gasoline-powered diesel, with a twist.

They just squirt a little soothing, cooling ethanol into the cylinder during peak demand (e.g., during high acceleration, hill climbing) to degrade performance. Yes, degrade!

This turns out to be more efficient in the real world, because that way you can run with higher compression ratios most of the time; however, when you really mash on the gas pedal, you won't damage the engine because it will never get to redline, thanks to a shot of cooling, pressure-lowering alcohol.

This approach allows you to have a smaller, lighter, higher-mileage engine because you're running it closer to redline, rather than a big V8 just loping along.

The higher-compression and lighter-weight engine
gives you the better mileage.

On the downside, the engine has to be more stoutly made, and with higher tolerances (like a diesel engine) which adds weight and increases machining cost. But even so, it's still worth it.

Anyhow, that's my theory and I'm sticking to it for now.

Sugar Frosted