Startup Working to Commercialize Direct Injection Ethanol Boosting + Turbocharging
25 October 2006
|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
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.
Posted by: allen_Z | 25 October 2006 at 12:00 PM
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.
Posted by: Sid Hoffman | 25 October 2006 at 12:36 PM
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).
Posted by: Rafael Seidl | 25 October 2006 at 01:19 PM
"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.
Posted by: allen_Z | 25 October 2006 at 01:33 PM
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.
Posted by: Sid Hoffman | 25 October 2006 at 01:57 PM
...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.
Posted by: Patrick | 25 October 2006 at 02:14 PM
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.
Posted by: mahonj | 25 October 2006 at 02:41 PM
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
Posted by: paul | 25 October 2006 at 02:57 PM
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.
Posted by: MadMax | 25 October 2006 at 03:01 PM
By the way, could this system work with methanol or buthanol as well?
Posted by: MadMax | 25 October 2006 at 03:04 PM
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.
Posted by: MadMax | 25 October 2006 at 03:07 PM
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.
Posted by: Sid Hoffman | 25 October 2006 at 03:23 PM
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.
Posted by: Harvey D. | 25 October 2006 at 03:31 PM
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.
Posted by: Mike Z | 25 October 2006 at 06:56 PM
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.
Posted by: Engineer-Poet | 25 October 2006 at 07:37 PM
Methanol would work great in this application because MIT is relying on the Latent Heat of Evaporation (methanol has a way higher LHE than ethanol) and Octane of the fuel to lower the knock limit. Since they are using small amounts, methanol would be even better than Ethanol.
Butanol would not work as well because it has a lower LHE and lower octane than either methanol or ethanol.
Also, the ECU would really not care what fuel(s) are used as long as there is a wide band sensor and the long term and short term trims are able to adjust to a wide variety of AFRs.
Posted by: Joe | 25 October 2006 at 07:43 PM
Methanol injection could act as a form of intercooling past the turbo compression stage. There might not be a need for an intercooler.
Posted by: SJC | 25 October 2006 at 09:13 PM
This sounds like a good idea, but for an estimated cost increase of only $1000, it is way too optimistic. The turbocharger with intercooler and wastegate control etc. will cost ~$2000 USD extra. And then, there is another set of high-pressure alcohol direct injectors with at least four of them, AND another high pressure fuel pump for these alcohol direct injectors, which will cost at least another $1000 USD. Plus an alcohol reservoir that must be strategically placed and protect from collision-induced fire hazard, since alcohol can burn without a flame that would at times be even more hazardous than gasoline with yellow flame. This is a concern in Indy Car Racing which uses methanol. Plus more careful calibration and higher quality sensors, better programming, etc. to avoid catastrophic engine destruction at high boost. It doesn't take long or much to destroy an engine from preignition at high boost.
Can ethanol injection be done via the same gasoline port injectors? Probably not, due to lead volume inside the injector, the time lag in introducing the ethanol hence the power boost may be longer than the driver would want when instant power boost is needed.
So far, I've tallied over $3000 USD to $3500 USD of extra cost for ~30% gain in fuel efficiency. By comparison, a Camry hybrid at 40mpg is 42% better than a 4-cyl Camry at 28mpg, and costs ~$4000-5000 USD more when compared to a 4-cyl Camry loaded with similar luxury options. The Camry hybrid accelerates much faster than the non-hybrid version, so some of the $4000 cost increase in the Camry hybrid is justifiable based on the increase in performance alone. Now, if the Camry hybrid was made to use the Prius' engine and drive train, the mpg improvement would be even more dramatic, perhaps at 60-70% that of the 4-cyl Camry, at comparable or slightly slower acceleration, but with even less cost differential, given the fact that Prius drive train is smaller hence cheaper and mass-produced at higher number.
Posted by: Roger Pham | 25 October 2006 at 09:29 PM
this sounds much better than hybrids:
no heavy unmaintainable battery pack waiting to die and cost $$$ to replace
more easily scaled up to high output
improvement in steady 70 mph efficiency, not just stop and go efficiency like hybrids
Posted by: shaun mann | 25 October 2006 at 11:33 PM
My Lord, what a shame for MIT.
Dual-fuel injection is established practice in performance cars for years. Port injection was proven decades ago to yield the best results because of:
1) evaporation of fuel in intake air makes air more dense;
2) cooled air has way lower viscosity, unlike liquids.
The best results are achieved with methanol/ethanol mixed with water injection, not just high-octane fuel. The practice of water injection into intake air is routinely employed on diesel engines. On high-performance gasoline engines it is standard feature even on semi-production performance cars.
Optimization of dual-fuel injection to downsize engine, boost effective compression ratio, and hence yield better fuel efficiency is really something new, but yield could be in the range of 5% gain max.
This hype is surely to compete with my “scum of the year” award with EESTOR and Hy-Drive.
Posted by: Andrey | 26 October 2006 at 02:07 AM
Fraid you're wrong there Andrey, DI even with gasoline achieves far better charge cooling that port injection as the fuel evaporates directly into the intake air during the induction stroke and does not pick up heat from the inlet valve and port wall which is what actually happens in a port injection engine.
This whole proposal could be massively simplified by just running the entire car as an FFV with boost pressure a function of alcohol fraction. Quite easy to acheive without the addition of a separate fuel system.
Most of the knock advantages can easily be achieved with DI and twin phasors by using alternative charging methods. Sounds like these chaps need to spend some more time playing with DI VVT....
Posted by: Ruaraidh | 26 October 2006 at 02:35 AM
Good old GM tried a version of this Circa 1962. Note the serious performance with only 5psi of boost, a single barrel carb, and no intercooler. The engine mentioned is currently still in use in Land Rovers. As for # of cylinders and small displacement, The Benelli Sei has a 750cc six, and is as smooth as a 3phase induction motor @ 60hz, IMO.
In 1961, the F-85 had a 155 HP version of the 215 ci. (3.5L) engine, and the Cutlass had a 185 HP version. The 1961 versions of the motor were rated at 155 hp, but later years saw increases - up to 200 hp normally aspirated for the Buick version and 215 hp in turbocharged form from Olds (the 62-63 Jetfire).
In 1962, Olds, along with AiResearch, introduced a 'turbocharged' (called Fluid Injection) version of this engine, which put "Turbo Rocket Fluid" (½ distilled water, ½ methyl alcohol) into the carb. Along with a 10.25:1 compression ratio, yielded 0-60 in 8.5 seconds (with the manual tranny). The turbo was a Garrett TO-3 with an integral wastegate, the first. Unfortunately, due to the 10:1 compression ratio, boost was limited to only 5 psi, not the best use of a turbo.
The induction setup itself is fairly sophisticated (especially for 1962), with something like 54 separate connections to the intake system. The turbo has an integral wastegate, being the first mass production turbo application to use a wastegate. This was arguably the most complex induction system build to that time, with something like 50 different hose connections in the intake system (pressure sensors, wastegate, fluid injection, fuel, etc).
Olds attempted to get around the boost lag problem by using a high compression ratio (10:1!), which limited boost to only 5 psi. Fluid injection (Turbo Rocket Fluid) was used (a water/alcohol mix) to suppress detonation. Properly running cars will not go into boost if the "Turbo Rocket Fluid" reservoir is empty. There is an automatic shutoff for this. Parts for this injection system are even harder to get than the turbo parts.
The carb is a rare single barrel Rochester side-draft unit, whose only other application was on the Corvair Turbo. While they resemble the Corvair carb, they are much larger.
The Olds' turbocharged Jetfire was supposedly quicker than the 4V version, but it had maintenance problems due to its complex mechanics for that era. It attained the magic goal of 1 HP per CID. A power boost on the order of 40% was claimed. The automatic Cutlass with 10.75:1 compression gave 195 HP @ 4800 and 235 lb/ft @ 3200. The Jetfire's 10.25:1 compression gave 215 HP @ 4800 and 300 lb/ft @ 3200.
Of course SAAB can give you this performance today with 140 ci (2.3L) or less.
Increasing BMEP is the answer, and biohols are the correct fuels for doing this in SI engines. Any serious arguments against MIT's work in this area have pretty much been made moot by Harry Ricardo. One would do well to start their research by reading his works.
Posted by: John Schreiber | 26 October 2006 at 03:03 AM
Think you'll find the P51 Mustang had water alcohol injection in WWII...
No ones arguing that alcohols aren't a way forward, just that this proposal is more complex than it needs to be to achieve the desired results.
I think you'll find the engine you're referring to hasn't been fitted to a Land Rover product for quite a while!!
Posted by: Ruaraidh | 26 October 2006 at 03:50 AM
I hope you're not working in purchasing. Your estimates regarding the extra cost are way too high. Turbos have become pretty cheap since European diesels all use them and, GDI is well on its way to becoming a commidity subsystem as well. Don't assume that just because US engine technology generally lags Europe and Japan by at least a decade that it cannot catch up quickly.
Posted by: Rafael Seidl | 26 October 2006 at 04:52 AM
I don't think that this will be cheaper to build than a Euro 6 turbo-diesel. Neither will it have the low-end torque needed for downsizing. Ford is probably looking for options to boost it's new 3.5L V6.
Posted by: JC | 26 October 2006 at 06:01 AM