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Ford E85 Direct Injection Boosting Study: A Less Expensive Alternative to Diesel

Using a separate E85 direct injection boosting system combined with gasoline port fuel injection (PFI) makes the engine more efficient in its use of gasoline, and can be viewed as a more cost-effective alternative to a modern diesel, according to a Ford study presented by Robert Stein, currently of AVL, formerly of Ford, at the SAE 2009 World Congress.

Proposed by John Heywood and colleagues at MIT in 2005, the basic premise of E85 boosting is that ethanol (or other lower alcohols) suppresses knock due to the large evaporative cooling effect it has on the air-fuel mixture when injected directly into the cylinder, supplemented by ethanol’s inherent high octane number. Using the E85 boosting concept requires two fuel tanks and vehicle owner acceptance of dual fueling.

With knock suppressed, the compression ratio (CR) can be increased; in a turbocharged or supercharged engine, even higher boost pressure can be used. The resulting higher BMEP levels allow downsizing of the engine at equivalent vehicle performance. The MIT team spun off a startup—Ethanol Boosting Systems, LLC (EBS)—in 2006 to commercialize the concept. (Earlier post.) EBS has a collaborative R&D agreement with Ford, and participated in the study reported at the World Congress.

The vehicle owner will realize high fuel economy because gasoline, with its greater eating value per volume, is the fuel that is primarily used for most driving modes. Furthermore, by enabling higher CR, downsizing and downspeeding, E85 DI + gasoline PFI makes the engine more efficient in itsusee of gasoline.

Improved engine efficiency leverages the effect of the limited supply of E85, compared to simply displacing gasoline as in an FFV [flexible fuel vehicle]...this leveraging can be very substantial, and has the effect of dramatically improving the net energy balance of ethanol, and therefore its beneficial impact on reducing petroleum consumption.

—Stein et. al. (2009)

In the study, Ford applied the E85 boosting approach to two engines: an early prototype 3.5-liter EcoBoost direct injection, turbocharged engine outfitted with PFI, and a 5.0L PFI engine in a Ford F-150 pickup truck.

Consumption of E85 varied under different operating and vehicle load conditions, and ranged from 1% to 48% for the 5.0L E85 DI + gasoline PFI engine in a pickup truck. Less E85 can be used by moderately retarding the spark timing, the researchers found, with a small effect on efficiency.

Among the conclusions reached in the study:

  • For a 5.0L E85 DI + gasoline PFI engine in an F-series pickup, the leveraging due to 12:1 CR is approximately 5:1 on the EPA M/H drive cycle—i.e., 5 gallons of gasoline are replaced by 1 gallon of E85. This leveraging effect will be significantly reduced for more aggressive drive cycles, they noted.

  • E85 usage in the scenario above is projected to be approximately 1% of the fuel for the EPA M/H cycle and 16% for the US06 aggressive driving cycle. With a 10 gallon E85 fuel tank, this rate of consumption would result in refueling intervals of approximately 20,000 miles on the M/H cycle and 900 miles on US06.

  • A 3.5L EcoBoost GDTI engine modified for E85 DI + gasoline PFI operation and constrained by a peak pressure limit of 125 bar demonstrated 27 bar BMEP at 2,500-3,000 rpm.

  • Achieving the full potential of an E85 DI + gasoline PFI engine requires an engine structure capable of at least 150 bar mean + 3 sigma peak pressure—comparable to a modern diesel.

  • An E85 DI + gasoline PFI engine is expected to have implementation advantages compared to a FFV GTDI engine operating on E85, including reduced dynamic range requirement for the DI pump and injectors, improved starting and emissions under cold temperatures, and potentially improved durability aspects (valve seat wear, bore wash, intake port/valve deposits.

  • There are a number of technical challenges associated with an E85 DI + gasoline PFI engine, including high peak cylinder pressures, combustion noise, and direct injector cooling.

The Ford team noted that the E85 DI + gasoline PFI can be viewed as an alternative to a modern diesel. Both engines use turbocharging, direct injection and an engine structure capable of high peak pressures; and both necessitate complex controls and calibration. A second tank is required for both: a urea tank for selective catalytic reduction (SCR) of NOx in the diesel, and the E85 tank for the DI + PFI engine.

There are a number of differences between the two, however:

  • If the vehicle owner does not fill the E85 tank, the engine can operate indefinitely with degraded performance using only gasoline. In comparison, a diesel SCR vehicle owner who does not refill the urea tank will experience a range of inducements including limited vehicle speed and eventually failure to start.

  • The DI + PFI fuel system of the E85 DI + gasoline PFI engine is less expensive than modern high pressure diesel injection system. The DI + PFI engine runs at stoichiometric air-fuel and uses a relatively inexpensive conventional three-way catalyst )TWC). The diesel requires more complex and expensive aftertreatment systems.

Because of these factors, the E85 DI + gasoline PFI engine will cost significantly less than a diesel engine, and will be able to achieve more stringent emission standards due to the extremely high conversion efficiency of a stoichiometric TWC aftertreatment system. The E85 DI + gasoline PFI engine also uses a renewable fuel in a leveraged manner to significantly reduce petroleum consumption and total net CO2 emissions.

—Stein et al. (2009)




Does this allow for the use of hydrous ethanol?


"E85 usage in the scenario above is projected to be approximately 1% of the fuel..."

SO for every five 20 gallon fill ups I need to add 1 gallon of E85. That does not sound bad at all.

Nick Lyons

It would be interesting to see and apples-to-apples comparison (performance, mileage) of vehicles equipped with this technology compared with current state of the art ICE. I can believe efficiency goes up--but how much, and how much better than simply downsized/turbo/DI (Ford EcoBoost, etc)?


"Using the E85 boosting concept requires two fuel tanks and vehicle owner acceptance of dual fueling"...which is why something like this will never be accepted by the masses...keeping track of one fuel level is nuisance enough, two fuel levels will be too much of a pain in the a s s.


I would say that if you injected E95 (5% water)you could get away with it. It is when you mix it with gasoline that you need to have no water. So you fill up with gasoline and the fuel station has E95 that you can fill the other small container with, it only has to be a gallon or so. Both fuel tank and container have level indicators on the dash. If you run out of gasoline you stop. If you run out of E95, no problem but no benefit either.


It is true that they would probably obtained the same result using water instead of E85(and that is not new at all, (Junker was using this trick on their WWII bomber aircraft) , and it would very easy to introduced. So much more hype than real


They wouldn't achieve the same result with water injection. Water injection does indeed retard knocking but the evaporative effect is about 1/2 that of an alcohol.

IMO, this seems like a very easy path to pursue. Advantages:

1. Diesel like efficiency
2. Gasoline or better emissions
3. Uses existing technology.
4. Minimial impact on existing infrastructure.

Aggressive downsizing while maintaining CR ~12:1, VVT on intake and exahust, mild hybridization, aggressive thermal management (ceramic thermal coatings inside cylinder, turbo, exhaust), and a multi speed or IVT would result in a 50+mpg with ~$2000 in additional equipment.

Roger Pham

This is great for performance-minded motorists looking to improve mpg at the same time. This is superior to the highly-powered fast HEV, like the Lexus 400H, Camry hybrid or the new Ford Fusion Hybrid, being too heavy (500-600 lbs over the comparable model). The extra weight of power HEV degrades handling and taking away trunk space.

However, an economy-optimized HEV like the new Honda Insight or Toyota Prius will still have an edge in term of maximum mpg gain per additional dollars in cost per pound of vehicle payload rating. With turbocharging and additional fuel injectors plus a second fuel tank plus additional sensors and electronics, there will be no saving in additional cost over that of the Honda Insight for fuel economy improvement.
Different strokes for different folks.


Green Please

Check your number the evaporative heat of water is way superior to ethanol


Actually Treehugger, the Germans only used straight water in emergencies. Their aircraft were designed to use MW50 (50% methanol, 49.5% water, and .5% anticorrosive oil). MW30, EW50 and EW30 were also used.

The only reason these people looked into E85 is that some gas stations are already selling it as a fuel, so you could have both FFV and Ethanol-boost cars refueling at the same pump.

Ofcourse if you only need to refill your alcohol tank once every 20,000 miles, and your car still runs fine without it, you don't have to do it at the pump. You could have it refilled when you go in for an oil change. This could be worked into a regular BFF(brakes, filters, fluids) servicing.

BTW a car designed to use 50/50 methanol and water could also use windshield washing fluid as a boost so maybe we don't need to add an extra tank, just enlarge one we already have.


Water is superior in that it has a high specific heat but it has a considerably higher flash point. An alchohol based fuel has the additional benefit of raising the affective octane of the fuel charge.

Any additional weight from injectors, fuel rail, lines, sensors, tank, turbo, etc. would be more than offset by a smaller engine and smaller gas tank. Gasoline weighs about 7lbs per gallon, Say ethanol weighs about the same. Say 1gal of ethanol allows us to reduce gasoline consumption by 40%, thus 40% less fuel is necessary onboard. Say the stock tank is 15 gallons. The net weight reduction would be 35lbs which should more than make up for the weight of an additional tank, injectors, etc.

Alex Kovnat

A nice thing about hybrid electric vehicles (perhaps using ultracapacitors along with lithium ion batteries) is, you can use stored energy in said capacitors and batteries to provide swift, smooth vehicle launch without using E-85 injection.

I still wish researchers all the best however, in solving the technical issues involved in breaking down cellulose from any plant source into sugar for fermentation into ethanol, so as to make E-10, E-15, or E-85 available for flex-fuel vehicles without using high maintenance crops like corn.


Here is a good read on methanol/water injection kits for turbocharged subarus...



FWIW, methanol/e85 injection also avoids issues of oil contamination that can occur with water injection if too much is used.


What I'd like to know is how much of a gain you could get with a retrofit? It's one thing to have a system that allows benefits through downsizing of the engine but what if you don't want/can't afford to buy a new car?


one big advantage to this system is that you can fill up both tanks with E85 if available and economical.. the engine will run just as well and efficiently.

If e85 is not available at the pumps then buy it in gallon containers at the local Ford dealership.

The disadvantage is that the engines will be as expensive (maybe a bit more, dual injectors) as diesel engines since they have to tolerate higher stresses, but perhaps not if mass produced like standard gasoline engines are.. and of course much cleaner emissions than even the cleanest diesels.

Looking forward to seeing this at the showroom.


Not necessarily more expensive than diesels. The primary fule line would be port injection (cheap) while the ethanol line would be direct injection (expensive). Overall, the cost due to injectors would be more expensive than even a modern DI engine but this would be offset by only needing a simple two way catalyst in the exhaust system.

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