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Startup Working to Commercialize Direct Injection Ethanol Boosting + Turbocharging

Ebs1
Ethanol boost with turbocharging promises a cost-effective means to obtain high fuel efficiency in gasoline and flex ethanol/gasoline powered engines.

MIT scientists and engineers earlier this year founded a company—Ethanol Boosting Systems, LLC (EBS)—to commercialize their work on direct-injection ethanol boosting combined with aggressive turbocharging in a gasoline engine. (Earlier post.) The result is a gasoline engine with the fuel efficiency of current hybrids or turbodiesels—up to 30% better than a conventional gasoline engine—but at lower cost.

EBS has a collaborative R&D agreement with Ford, and anticipates engine tests in 2007 with subsequent licensing to Ford and other automakers. If all goes as expected, vehicles with the new engine could be on the road by 2011.

The foundation of the approach is the enhanced knock suppression resulting from the separate, direct injection of small amounts of ethanol into the cylinder in addition to the main gasoline fuel charge.

Efforts to improve the efficiency of the conventional spark-ignition (SI) gasoline engine have been stymied by a barrier known as the knock limit. Changes that would have made the engine far more efficient would have caused knock (spontaneous combustion).

The injection of a small amount of ethanol into the hot combustion chamber cools the fuel charge and makes spontaneous combustion much less likely. According to a simulation developed by the MIT group, with ethanol injection the engine won’t knock even when the pressure inside the cylinder is three times higher than that in a conventional SI engine. Engine tests by collaborators at Ford Motor Company produced results consistent with the model’s predictions.

With knock essentially eliminated, the researchers could incorporate into their engine two operating techniques that help make today’s diesel engines so efficient: a high degree of turbocharging and the use of a higher compression ratio.

The engine would operate with a wide range of ethanol consumption from a minimum of less than 5% up to 100%. A knock sensor would determine when ethanol is needed to prevent knock. During the brief periods of high-torque operation, fractions of up to 100% ethanol could be used. For much of the drive cycle, vehicles are operated at low torque and there is no need for the use of ethanol.

The combined changes could increase the power of a given-sized engine by more than a factor of two. But rather than seeking higher vehicle performance, the MIT researchers cut their engine size in half. Using well-established computer models, they determined that their small, turbocharged, high-compression-ratio engine will provide the same peak power as the full-scale SI version but will be 20 to 30% more fuel efficient.

The ethanol-boosted engine could provide efficiency gains comparable to those of today’s hybrid engine systems for less extra investment: about $1,000 as opposed to $3,000 to $5,000. The engine should use less than five gallons of ethanol for every 100 gallons of gasoline, so drivers would need to fill their ethanol tank only every one to three months. The ethanol used could be E85.

Given the short fuel-savings payback time—three to four years at present US gasoline prices—the MIT researchers believe that their ethanol-boosted turbo engine has real potential for widespread adoption.

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

—Daniel Cohn, MIT senior research scientist and CEO of EBS

Resources:

Comments

allen_Z

2 fuel tanks, one that collects water due to ethanol's chemical nature. The potential to downsize the engine is nice...but having E-85 or ethanol available at every other corner gas station is going to be a challenge.

Sid Hoffman

It doesn't need to be on every corner, you'd only fill up the ethanol tank every 3 to 10 refills depending on how big your gasoline tank is and how much high-torque operation you use. Once the ethanol runs out it would just limit the turbo boost to a very low level until you filled up the ethanol tank again. It's a very creative way to satisfy both the desire to run good old regular gasoline for economy but still have all the power of a big engine.

The only major downside I see here is that typically highly boosted engines have the most turbo lag since on a low bost engine, it just adds another 30% more atmospheric pressure to the manifold - this implies they're going to run 1 bar or more (100% or more additional manifold pressure) which tends to translate into a strongly felt rubber band effect common to older turbocharged engines.

Rafael Seidl

Interesting concept, though downsizing with regular GDI with cam phasers and intercooled turbocharging plus thermal management and mild internal EGR in part load already yields 15-20% today, without the need to maintain a second fuel tank.

Another general issue is customer acceptance of downsized engines, especially in upmarket models. Even with compensation shafts, a turbocharged I4 will exhibit greater vibration and a different sound than a V6. Turbo lag is perceived negatively. Moreover, high engine displacement has long been a status symbol.

Btw, turbo lag can be masked in a number of ways, e.g. with an electrically powered supercharger (e-booster). This requires either a high voltage grid or, power electronics plus dedicated supercaps. VGT turbos, which also sharply reduce turbo lag, cannot long tolerate the very high engine-out temperatures of SI engines running at nominal power. Either the duration of such excursions has to be managed via the engine controls or, very expensive exotic materials must be used (cp. current Porsche 911 Turbo).

allen_Z

"every other corner gas station"
Not at every corner, or even at every gas station. Most gas stations are at street corners/intersections. Perhaps it would be more accurate to say "every other gas station" or "every few gas stations", or something like that.

Sid Hoffman

If status is a big deal, you can do small displacement 6 and 8 cylinder engines. Mazda sold a 1.8 liter V6 in the MX3 in the 1990's. Ferrari actually had something like a 2 liter V12 if you go all the way back and sold a 3.5 / 3.6 liter V8 car in the 1990's and up until a year or two ago. V8's go very well with cylinder deactivation so there's nothing saying you can't have a 2.8 liter V8 with a turbocharger and cylinder deactivation. Most folks just care about the V8 status and having lots of power, not the displacement.

Patrick

...and in the early 90s Mitsubishi had a 1.6L V-6 in the Mirage Cyborg before they went to the 1.6L MIVEC I-4.

mahonj

Most engines in Europe are I4's. People do not have the V8 fixation that they have in the US. Could go well over here, although it competes with diesel which is already very efficient. However, it could be a good way to use up some ethanol.
What is most important is the way these guys are thinking "outside the box" and the ideas they might spark in other engineers.
Nothing like $60 a barrel oil to get a few ideas rolling.

paul

A very creative idea. I could see some usability issues i.e. what happens if you fill the ethanol tank with gas by accident or fill the gas with ethanol. This would need some extra safety controls. I would be fine with the idea. However, I could see non-technical people having a problem with two fuel systems

MadMax

If a full tank is 20 gallons, at 5% ethanol should be only one gallon. Then you do not need a pump, you can simply buy a can at the gas station to fill in.

MadMax

By the way, could this system work with methanol or buthanol as well?

MadMax

And there is no problem if the ethanol picks up a little water. If I remember the MIT paper ethanol with 5-10% water works equally good. And it is cheaper to produce.

Sid Hoffman

Methanol and butanol have totally different calorific count, or energy density, or whatever you want to call it.

Methanol: 55,000 btu/gal
Ethanol: 78,000 btu/gal
E85: 82,000 btu/gal
Butanol: 105,000 btu/gal
Gasoline (for reference): 110-114,000 btu/gal

It makes it extra hard to do precise fuel metering if you're not sure what's in the tank. The good news is all the alcohols have reasonably similar octane values, so in that sense, any of them would work reasonably well.

Harvey D.

At $1000 it sounds good for people who like/need frequent power boosts. Would it be effective on a Toyota Prius or Honda Hybrid? Would it allow the use of smaller, lighter ICE generator?

Adding a one gallon plastic ethanol tank should not be a major problem. Fill-ups with reusable one gallon ethanol Jerry cans such be simple enough.

Could it be combined with windshield wipers liquid? Low quality ethanol is a good glass cleaner.

Mike Z

Interesting idea, but couldn't a similar system use high octane gasoline? If there were a way to not destroy the catalytic converter such a system might get much higher MPG if the injector used 120 octane leaded gasoline. Nasty, but might be worth a cost/benefit before we judge it too much.

Engineer-Poet

One thing nobody's noted so far:  ethanol (and methanol) burn much cooler than gasoline, so operation on 100% alcohol for maximum power would stress the turbo's hot section a lot less.  Doubly so if there was a substantial fraction of water in the alky.

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