How a Hydrogen-Boosted Gasoline Engine Works

BMW's recent concept car, the hydrogen-powered 7-Series, is still a long way from arriving at dealerships.

Faced with the ever-increasing cost of gasoline, automakers worldwide are working overtime to cost-effectively improve vehicle fuel economy while still meeting today's strict emissions requirements. One promising way to boost fuel economy is to add hydrogen to the fuel/air mixture in a conventional gasoline engine. It's called a hydrogen-boosted gas engine. However, since hydrogen isn't readily available at your local filling station, selling a hydrogen-boosted gas engine hasn't been on any automakers' short list. Until now, that is.

In this article, we'll explain a new technology that utilizes a fast-response on-board reformer to generate a small amount of hydrogen from gasoline. This hydrogen is added to the engine's normal air/fuel mixture. Engines designed to run on a mix of hydrogen/gasoline can see a fuel-economy gain of 20 to 30 percent with no requirement for control of harmful NOx emissions, oxides of nitrogen. On the next two pages, we'll tell you how this new fuel-saving engine works and why it looks like it has the potential to become a viable, fuel-saving technology. We'll address the following issues regarding this new technology:


  • What Is a Hydrogen-Boosted Gasoline Engine?A small amount of hydrogen made on-board by the reformer is added to the normal intake air and gasoline mixture in the vehicle's engine. This greatly improves overall combustion quality by allowing nearly twice as much air for a given amount of fuel introduced into the combustion chamber. This is more energy efficient because it saves energy by reducing the amount of engine pumping needed. Learn what the experts are saying about this new technology.
  • The Future of Hydrogen-Boosted Gas EnginesThe race is on for the fuel-economy leadership position. Where will the hydrogen-boosted gas engine fit in with other fuel-saving technologies like hybrid cars, E85 ethanol-powered vehicles, and new clean diesel-powered cars. How much gas does it save compared to other alternative fuel-powered vehicles? Will consumers begin seeing this type of engine in cars in the near future? Find out in this section.

ArvinMeritor This prototype reformer, mounted close to the engine for testing in a V6 SUV, is 18 inches long by 4 inches in diameter.

Hydrogen-boosted gasoline engine technology is new and just now beginning to emerge from the laboratory. It offers the prospect of an economic way to produce a small amount of hydrogen from gasoline with an on-board system designed to do so. Invented by scientists at the Massachusetts Institute of Technology, and being perfected by auto industry supplier ArvinMeritor in cooperation with the German automotive engineering firm IAV, this system may provide a cost-effective alternative to fuel-cell technology and traditional gasoline- and diesel-combustion engines. It's possible that hydrogen-boosted engines could bridge the gap between today's gasoline-powered vehicles and the fuel-cell vehicles of the future.

While fuel-cell vehicles may hold long-term promise, the reality is that they are years away from mass production. Critics cite the high cost of fuel-cell stacks, hydrogen fuel mass-production issues, and general fueling problems as key stumbling blocks. Some believe it may be decades before fuel-cell vehicles become widely available. European automakers have already turned to more expensive diesels but their cost and related complexity is increasing with stiff new emissions requirements for control of particulate matter and NOx emissions.

U.S. carmakers faced with the same concern about diesels are reluctant to commit to the huge expense required by the changeover from gasoline to higher-cost diesel. For example, consumers currently have to pay about a $3000 premium for a diesel-powered light truck vs. a conventional gasoline-powered vehicle. This will increase in the future to compensate for the rising costs associated with making sure diesel vehicles meet forthcoming emissions regulations. The EPA has recently granted diesel vehicles a break by easing near term NOx requirements, but only through 2009 and the high-mileage emissions requirement has been tightened as a trade-off.

What the Experts Are Saying

According to experts at ArvinMeritor, and executive engineers Rudy Smaling and Jens Beister at IAV, the facts about a hydrogen-boosted gasoline engine and its advantages are clear.


A small amount of hydrogen made on-board by the reformer is added to the normal intake air and gasoline mixture. This greatly improves overall combustion quality by allowing nearly twice as much air for a given amount of fuel introduced into the combustion chamber. This is more energy efficient because it saves energy by reducing the amount of engine pumping needed.

Fuel efficiency is also gained through the use of higher engine compression ratios made possible by the hydrogen-rich charge characteristics. A hydrogen-boosted fuel system also saves energy because of the remarkably low amount of electrical energy needed to power the reformer. According to the developers, it needs less than 75 watts, which is less than the electric needs of one standard headlight.

An industry-accepted virtual vehicle analysis based on engine test data indicated the potential for a 20 percent to 30 percent improvement in fuel economy for a turbocharged downsized version of the hydrogen-boosted engine when compared with conventional gasoline engines.

Next, we'll explain what's in store for this technology and where consumers will begin to see it. 

Imagine a full-size SUV like the Toyota Sequoia [bottom] that gets the fuel economy of a large sedan like the Ford Five Hundred [top]. The hydrogen reformer could make that a reality.

Hydrogen-boosted gasoline engines have the potential to considerably improve fuel economy. A major cost and environmental advantage of the hydrogen-boosted lean system engine are low amounts of NOx emissions gasses, hence, complete elimination of the need for external NOx emissions control. Currently, NOx emissions control is a major cost problem for diesels which use expensive traps to meet emissions standards. Diesel particulate emissions must also be collected by a filter that must be periodically regenerated.

Hydrogen-boosted gasoline engines require neither NOx or particulate control filters and require only a low cost oxidation catalyst to control small amounts of exhaust (unburned hydrocarbons) formed mostly during engine start-up and early warm up. Additional cuts in emissions control requirements stem from the engine's ability to use only the clean hydrogen enriched charge during the cold start phase when 90% of emissions are generated in the emissions test.

The hydrogen-boost system is effectively a bolt-on technology that can be added to an existing vehicle's engine compartment. According to the developers, the cost of the system is less than half of the added cost for diesels. U.S. auto industry production costs for tooling diesels to replace gasoline engines are enormous and would be difficult for U.S. makers currently struggling with financial difficulties.

A prototype hydrogen-boosted engine is now being installed in a V6-equipped SUV that has sufficient free space for the reformer and its related system. The start of long-term road testing for performance, reliability, and durability information is planned for later this year with the first production application marketing expected for 2010.

Performance data generated during the early phase of testing is certain to be watched intensely by virtually everyone concerned with automotive and energy environmental matters in part because the system is associated with the buzzword "hydrogen."

High on the list of interested parties are makers of the large SUVs and vans for which government regulators are seeking 10 percent higher average miles per gallon vs. the 2007 level of 22.2 mpg. The new level of 24.1 mpg is to be adhered to by 2011.

Four-cylinder vehicles will likely also be prime candidates for the technology as high gasoline prices continue to generate competition among the high fuel economy models seeking mpg leadership. A contributing factor in the compact car market may be a concern with hybrid vehicle lifetime cost due to system complexity and battery replacement, reported in some cases to be as high as $5000. This is just now beginning to be reflected in low resale values as early production hybrids reach high mileage.

The hydrogen-boosted engine will not be alone, however, in the race for fuel economy leadership position. Advanced turbocharged downsized direct injected variable valve engines, common-rail diesel engines, hybrids, and flex-fuel vehicles are all vying for the automaker's attention in the fuel-economy race.

None of these technologies can boast all of the advantages of the hydrogen-boosted engine, namely dramatically increased fuel economy, minimal emissions control, and overall cost-efficiency. In the end, it will take a combination of many technologies to address this nation's thirst for driving freedom, but it's likely that we'll hear a lot more about the hydrogen-boosted engine in the future.