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Hydrogen-Enhanced Combustion Engine Could Improve Gasoline Fuel Economy by 20% to 30%

An HECE test engine

Work being done by ArvinMeritor, IAV (Ingenieursgesellshaft für Auto und Verkehr) and MIT on enhancing gasoline combustion with a small hydrogen gas stream is pointing toward a potential estimated improvement in gasoline fuel economy of 20% to 30%, depending upon the baseline engine.

Writing in the October issue of MTZ (Motortechnische Zeitschrift), Utz-Jens Beister from IAV and Rudy Smaling from ArvinMeritor describe their progress with the Hydrogen-Enhanced Combustion Engine (HECE) concept, as applied to an SUV-class 3.2-liter V6 test engine.

The premise of HECE, on which the research collaborative has been working for a number of years, is that the addition of a small amount of hydrogen to the cylinder charge can allow homogeneous charge ultra-lean-burn combustion engines to operate much leaner than otherwise possible.

That in itself is not a new discovery. What brings HECE closer to operational reality is the ArvinMeritor/MIT on-board, compact plasma reformer (earlier post) that can take a fraction of the conventional fuel, reform it in real-time and add the resulting hydrogen-rich gas to the remaining fuel-air mixture flowing into the engine.

In the plasma fuel reformer, air is metered into a plasma generator located upstream of a combustor. High voltage is applied to the air stream, forming high-temperature plasma. This high-temperature plasma torch flows into the combustor, initiating vigorous combustion of a rich fuel-air mixture. Within the plasma fuel reformer, partial oxidation reactions occur in the high-temperature gas phase created by the plasma, eliminating the need for a reforming catalyst.

The shift of combustion limits with hydrogen-enhanced combustion.

Adding hydrogen gas to the homogeneous fuel charge improves the ignitability of the mixture, and increases flame speed and combustion stability. In theory, the combination of a lean-burn engine with the plasma reformer could support an ultra-lean and turbocharged engine that would reduce NOx emissions to the point of not requiring aftertreatment in the exhaust stream.

Researchers at the Sloan Automotive Laboratory at MIT also discovered that both hydrogen and carbon monoxide (both products of the partial oxidation process of the reformer) act as octane enhancers. Adding the reformed fuel gas to the engine thus also supports a substantial increase in compression ratio.

Once an engine is developed that operates ultra-lean, is turbocharged—or super-charged—and is better able to withstand engine knock, engine downsizing while maintaining performance becomes a credible option that can lead to significant additional fuel economy and performance benefits.

—Beister and Smaling

Such an ultra-lean-burn, high compression-ratio, turbocharged HECE could exhibit the following characteristics:

  • Extremely low engine out NOx emissions requiring little or no exhaust emissions control

  • Reduced pumping losses (~5-10% efficiency gain)

  • Improved thermodynamics (~10-12% efficiency gain)

  • Reduced friction (downsizing) (~5-8% efficiency gain)

ArvinMeritor is targeting release of the HECE for approximately 2008.



Jesse Jenkins

So the small amounts of hydrogen used in this system are reformed onboard out of the gasoline fuel? Am I right that this system does not need an external hydrogen fuel supply?


That’s correct. The on-board reformer takes a little bit of the gasoline and converts it to the hydrogen-rich gas. No external H2 supply is used.


Thats so cool. Sci-fi stuff, accept without the fiction.


20-30% more efficient? Isn't that called a `diesel'?



"Adding hydrogen gas to the homogeneous fuel charge improves the ignitability of the mixture, and increases flame speed and combustion stability."

Correct me if i am wrong, how can H2 improve flame speed when H2 has a slower flame speed then gasoline?

"High voltage is applied to the air stream, forming high-temperature plasma."

So can a car alternator supply this kind of high voltage?

Lance Funston

This development combined with the very interesting work Honda is doing on HCCI systems could continue to drive serious improvments in the basic ICE.

Were these technologies compatable (HCCI adds say 30% efficiency plus H2 injection adds another 20% efficiency) and soon you're seeing some very impressive numbers even before you add your start-stop and/or hybrid systems.

This could get your average passenger car from 25 mpg to 50 mpg without hybrid, and perhaps beyond 60 mpg with hybrid. Now put it on a diesel...

Harvey D

Lance: Yes, if all the most efficient technologies were integrated in the same diesel engine, a compact car could easily do 80 + m/gal. This car already (almost)exist, a small super sleek roadster made in Germany, but only a few hundred were produced. It's called the JetCar and you may look it up on the WEB.


I ride to the shops every once in a blue moon on my bike just because its close enough. Otherwise all car.

Never do I see anybody jogging or even walking their dog.
Some dude in a magazine said that the generation before us walked something like 30 times more. Its not like they didn't have cars back then.

Maybe half the problem with the modernised world is people rely too much on automobiles when alternatives are just as good.

In conclusion, a further 10% saving in fuel if you do your daily meager shopping using a backpack and a bicyle.


I believe the H2 system is for spark ignition ICE, because they mentioned improving flame speed. With hydrogen rich gas less fuel is needed to make the mixture explode inside the cylinders.

HCCI engines suppose no need to worry about flame speed because the ignition happened almost simultaneously(and here's where the efficiency come from).

H2 system on a HCCI engine. IMHO, will increase the efficiency by having a higher compression ratio. Because with H2 gas maybe the mixture can withstand greater compression before auto ignite.

Now put tat thing on a start stop hybird. And adjust the powerplant to drink diesel.

It can be done, nothing can't. All we need is lots of money and time.

20 years?



The JetCar is sort of a motorbike with roof. Just like the discontinued VW 1L if i remember correctly.

Harvey D


It is a beautiful, aerodynamic, very light weight 4-wheel, very sleek, 2-passenger roadster with a 800 cc 3-cyl diesel engine, 6-gear transmission, max speed 160 Kmh, trunk space 181 liters, fuel consumption 2.5 liter/100Km, Co2 = 66 g/Km

Fran Giroux

Hydrogen injection in ICE engines has been around since at least 1920, patented. Many companies produce electrolyzers for vehicles, spark ignition and diesel. Hydrogen Boost offers hydrogen injection and other mileage enhancement devices and procedures. We have achieved 100 mpg on three vehicles. Two are 4-5 passenger cars in mileage competition type driving conditions and the third is a two wheeled enclosed vehicle called a personal transport vehicle seen on the bottom of this page driving at normal highway speeds.
50-60 mpg in my Hydrogen Boosted Saturn SL1 is common.


While I've long argued that the hydrogen fuel cell technology is a waste of time, I haven't argued against hydrogen as a fuel or fuel-enhancer applied to Hybrids. The 'Plug-in' hybrid drive train is still the most practical and advantageous vehicle technology. Vehicles need weight to perfect handling, stability and crash tests. Adding the weight of plug-in batteries is desirable for this vehicle safety factor and creates an invaluable homepower supply. Energy corporations do not wish to have their cash cow gored and so oppose Plug-in Hybrids.

I argue that 'Start-Stop' Hybrids should not be classified as true hybrids. The 'start-stop' feature produces minimal fuel economy and emission reduction. It is the automobile industry's idea for maintaining bumper-to-bumper gridlock.

Carl Dunphy

As I presently own a gasoline powered vehicle, to utilize the hydrogen fuel cell technology, would necessitate the purchase of a new vehicle, which I am not prepared to do.
For this reason, I have been searching for an alternative and practical way to use hydrogen as a fuel. A Canadian company has developed an on board hydrogen generator to inject a hydrogen additive to the fuel line and enhance the mileage by as much as 20-25%, using only water in a holding tank. This has been the closest anyone has come, so far,to what I am looking for, however, I would like to cut the gasoline out of the equation altogether. Everyone seems to be plunging into developing a better fuel cell- why is no one looking at a way to develop an on board system to efficiently produce only the hydrogen necessary to fuel an internal combustion vehicle as it runs. No hydrogen storage tanks-liquid or compressed-just water tanks. I read about a car an Israeli company is developing but the changing of a large coil at regular short intervals seems to be required and seems quite cumbersome. It involves service stops to vacuum out metabolic waste as well. Perhaps if someone was to use a voltage inverter on one of these mileage enhancing devices he may come closer to my dream.


"Produce the hydrogen required to fuel the vehicle on board; just water tanks" So what do you plan to use as a power source? Or would this be a highly advanced perpetuummobile?

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