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Mazda Delivers First Hydrogen Dual-Fuel Rotaries to Customers

Hydrogen RE with Iwatani International badging.

Mazda Motor Corporation has delivered one RX-8 Hydrogen RE vehicle each to its first two corporate customers for this model: Idemitsu Kosan Co., Ltd. in Tokyo, and Iwatani International Corporation in Osaka, Japan. (Earlier post.) This marks the first commercial leasing of a hydrogen-gasoline dual fuel vehicle.

The RX-8 Hydrogen RE is equipped with a rotary engine, and features a dual-fuel system that allows the driver to select either hydrogen or gasoline with the flick of a switch. The vehicles that have been leased to these first two corporate fleet customers are based on the original body design but with specially added company decals for each customer’s use.

We’re pleased to deliver these hydrogen rotary engine vehicles for fleet use in these two companies, which are participating in the Japan Hydrogen and Fuel Cell Demonstration Project (JHFC) and are actively engaged in advancing further uses of hydrogen energy.

And we are looking forward to hearing feedback from our customers about the cars. Mazda will continue its efforts to improve the performance of hydrogen-fueled rotary engine vehicles and do its part to help achieve a more environmentally friendly hydrogen energy society in the future.

—Akihiro Kashiwagi, RX-8 Hydrogen RE development program manager

The hydrogen range of the vehicle is limited: 100 km (62.1 miles). The car stores 110 liters of hydrogen compressed at 35 Mpa (350 bar).

The RENESIS Hydrogen RE incorporates an electronically controlled hydrogen gas injector system. The system draws air from the side port during the intake cycle and uses dual hydrogen injectors in each of the engine’s twin rotor housings to directly inject hydrogen into the intake chambers.

For future versions of the rotary hydrogen cars, Mazda plans to incorporate the RENESIS hydrogen rotary engine with the emerging Mazda Hybrid System and an electric-motor-assisted turbocharger to enhance efficiency as well as the driving experience.


Rafael Seidl

More greenwashing I'm afraid. Rotary engines have many great qualities but fuel efficiency is not one of them: the shape of the combustion chamber is very elongated, neccessitating two ignition points. The special geometry of rotaries precludes compression ratios high enough for diesel combustion.

On 91 octane gasoline, the RX-8 has an EPA rating of 22MPG combined, which is hardly stellar. Add to that that rotaries like to rev high, which means combustion is less isochoric and less complete, and you can see why this type of engine is the last thing that you should put on a steady diet of super-expensive hydrogen.

Paul Berg

Heeey Mr Rafael... It´s a beginning man...this kind of action is what we are all waiting for...production...so the prices can go down and the car industry is really starting to feel the heat of competition...100 km of hydrogen range is not enoguh that either but its better than 1 km of gasoline...right ? Best Reguard Paul Berg, Västerås, Sweden.

Rafael Seidl

Paul -

you can fool some of the people all of the time, and those are the ones they want. They being the California air resources board and various energy lobbies.

The list of problems with hydrogen as a transportation fuel is very long: production, distribution, storage at filling station, filling process, in-vehicle tank, engine/fuel cell, crash safety. Of these, hydrogen production is perhaps the most serious, as you either have to reform natural gas (produces a lot of GHG), sacrifice a lot of land to solar and wind parks (extremely expensive) or, build a lot of new nuclear power plants (somewhat dangerous and extremely dirty).

Better to spend the research dollars on improving fuel economy (plenty of opportunity for that left in ICE drivetrains and car chassis) and, on producing affordable renewable fuels (cellulose ethanol, biodiesel).

I suspect that like BMW, Mazda is just doing this to fulfill their California ZEV requirements. Those are starting to bite this year, and converting an ICE requires the least incremental engineering while making them look oh-so-green. Rest assurd they will actually build as few of these as possible, and IMHO that is wise.


These vehicles, of course, do not meet true ZEV requirements, unless, of course, you ignore the ghg released to reform the fuel. More bullshit from a company which should have mothballed their rotary engine years ago.

Paul Berg

The costs you are talking about are Zero compared to the cost our children will pay if we continue using gasoline as enegy source around the world. Even if the car companys try lowering the fuel economy in their cars we will still be screeaming to drastically lowering the amount of carbon dioxide levels. Ethanol and diesel as you mension are still letting out carb... We need many Zero emisson vihecles today...right now... the ice is melting you know...so lets give Mazda and all the great engineers of the world a BIG BREAKE !!! Many Reguards, Paul.



The climate has shifted several times over the past few thousand years (See: Medieval Warm Period, Little Ice Age). It's as much in our interest to prevent another Ice Age. The climate will go on changing no matter what we do. Adaptation is key. And we humans are nothing if not adaptable.

Rafael Seidl

t -

CARB actually tried to establish emissions limits for CO2 but was immediately taken to court because that would be an indirect way of dictating fuel economy. Legally, only the federal government - which is beholden to Detroit - is allowed to do that.

Paul -

I'm an engineer. Don't panic. The arctic still has an iceberg or two.

All I'm saying is there are quicker, less risky and above all cheaper ways to achieve far greater reductions in net CO2 emissions than switching cars to hydrogen.

Example: downsizing a regular gasoline engine, adding a turbo and adjusting the transmission shift points will improve efficiency by 10-15% by moving the engine operating point to higher load. Turbo lag and peak torque can be addressed with an ultracap-based parallel hybrid powertrain, yielding an extra 10% fuel economy. The result is a power plant that feels just like an aspirated engine with 1.5x the displacement.

Another example: air conditioning of buildings and artificial lighting each consume a big chunk of the total electricity generated in power plants. Shift the burden of taxation away from income and towards environmental damage and the picture will improve accordingly.

Final example: at least 100 billion m^3 of natural gas (roughly equal to the combined NG consumption of Germany plus France) are simply flared off in oil production every year, most of it in just 10 countries incl. Russia, Saudi Arabia and Nigeria.

When considering GHG emissions, you need to look at all global sources and options, not just one aspect of one sector of the economy of one state of one country.

Barry R. Guthrie

Forget about GHG with Mazda's rotary engine.
They have tremendous combustion process problems enough that they need to put unburned fuel into the EGR of the next engine cycle.

Although hydrogen has a faster flame front they will still have problems combusting all the fuel before exhaust. The hydrogen is so powerfully diffuse that much of the hydrogen will not go into the EGR of the next engine cycle but out of the engin into the exhaust.
Depending on the concentration this could be a big explosive problem. To account for this they will have to lean the fuel mixture more and loose power and performance.

It is highly problematic combustion/emission problem and worse with hydrogen. I'm not sure how they got the hydrogen emissions past CARB?


Barry, your facts are slightly wrong.

There is no EGR used in the renisis rotary as far as I know.

The prime reason that mazda use lean burn strategy when running on hydrogen is due to the fact that hydrogen burns EXTREMELY fast, its more like an explosion that a combustion event. To prevent shock damage to the engine internals, less hydrogen (with a large amount of excess air) is used. The air acts like a cushion, absorbing the energy released during the combustion event, and then releasing it in a more adiabtic fashion during rotor expansion.

As hydrogen burns so quickly and cleanly there is no question of unburnt hydrogen in the exhaust stream. The only issue I can think of would be high Nox emissions.
As hydrogen burns so fast it is an ideal candidate for use in such a long and thin combustion chamber, which does not lend itself to burning gasoling very well.

The rotary engine will actually be more mechanically efficient (BTU's of hydrogen in vs. kWh energy out) when running on hydrogen, but thats not saying much as its pretty crap to begin with.

I'm still not convinced about hydrogen as a vehicle fuel. I'm inclined to think that bio fuel is better along with conservation.
The technical challenges faced with hydrogen are just too great, unless someone comes along with a paradigm shift type invention, that completley moves the goalposts.
Even then, there's still basic physics to overcome, like the huge quantity of energy needed to create the H2 in the first place.



Whoa fellas, why the rotary bashing? The RX-8 is a lot of car to haul around, and if you like to have a little fun making the rev limiter go off on a regular basis, then yes...your mileage will be terrible. Go easy on it, and you will get respectible mileage. I averaged around 27 mpg in my 87 RX-7 on the highway and 25 mpg in my 90 RX-7 GTU-s at 80mph taching 4000rpm. The rotary is not a gas sipping design, its much better for its high power to engine package volume ratios. Why mazda is powering a 3200lb car with an engine you are supposed to cram in a 2000lb sports car is beyond me. Hydrogen combusts better in a rotary than a piston engine due to the relatively cool intake zone, as in it doesn't preignite and blow your engine as it does in piston engines without special control. Its hard to make a lot of power with H2 as well. At UCR we had a couple of guys running a 8L v8 shelby cobra on H2, and it would dyno at around 200hp at the wheels, and you were lucky if you could fill it up, then make it to the taco stand and back before running out of H2, because the H2 storage density was so low in the compressed gas tank.

Barry R. Guthrie

Hi Andy,

With the EGR I refer you to SAE 2004-01-1790 Developed Technologies of the New Rotary Engine (RENESIS).

The unburned HC which is significant in rotary gasoline engines, I agree will not be as bad in hydrogen version, will accumulate near the trailing side of the chamber near the apex seal. The old 13B has radial exhaust ports, but the new Renesis has axial exhaust ports that are above this concentration of unburned HC. The unburned HC are recirculated into the next cycle process. This is a big problem of the problematic incomplete combustion process creating thermal trottling of unburned HC EGR that reduces the fresh intake air volumetric efficiency. This reduces overall power and performance.

Mazda has developed a three staged Sequencial Dynamic Air Intake system (S-DAIS) that uses three different intake ports that open up in sequences as rpm increases. This does dramatically improve the volumetric efficiency, but is very complex, expansive, and operationally problematic. It may be good for high end racing applications, but not practical for normal everyday drivers. Brett may be the exception. :-)

The hydrogen Renesis sounds great for power and it does supply high power density to volume and weight, but the BTE is terrible and would require larger H2 storage capacity to be usable. The extra H2 storage would be much larger and more heavy weight that it would off set any benefit of high power performance and power density to volume and size benefits.

The BTE problem is even more problematic at higher rpm where you want your power. Even with very fast H2 laminar flame front speed it will still not combust before exhaust. Here again they would have to lean the mixure or reduce the rpm or risk H2 emissions.


why are we talking about ZEV requirements? as far as i know they were supposed to take effect in 2000 but then got lifted by the powers that be due to "difficulties" being experienced by automakers trying to comply.


Thanks for the backup Barry! Burning hydrogen just isn't really a practical idea. Fuel cell vehicles can't cram enough H2 on-board to run the vehicle over 400 miles, and they utilize it at a much higher efficiency than ICEs (roughly double). So unless some ridiculously high density H2 storage comes along, H2 ICE cars aren't going to run far before needing refueling.


Let me get it straight.

To begin with: put a most compact IC engine in FRONT of RWD performance coupe? With bulk weight of 3000+ lb?

Then add bulky hydrogen tank to fuel the least fuel efficient IC engine.

Then add heavy battery pack and make it a HYBRID.

Then add turbocharger to SI engine with hybrid drivetrain.

Then add electric booster to turbocharger.

And all these to reduce GHG emissions?


Zach Hall

Is there no way to make hydrogen on the fly from water? Couldn't there be a battery pack that is charged at home (or anywhere with an outlet), than the energy from the battery pack could be used for electrolysis of water to form hydrogen, then it could be combusted. I think a tank that holds water, a reaction chamber (where the electrolysis happens), and a battery pack would be less dangerous, more economical, and give a longer range than a pressurized hydrogen tank, as well as being more cost efficient. I agree that zero emmissions cars need to be available about now! Whatever the solution, I want to understand the technology that works and makes sense. Honestly I think that electric vehicles are probably one of the best ideas, or atleast hybrid (maybe a generator that charges batteries...different type of hybrid). I'm going to college to learn about all of this shit, I wanna make a difference! I agree, right now ethanol and biodiesel are options that need to undertaken now! Atleast blends to reduce the emmissions. I think any alternative fueled vehicle is great, atleast something is learned about the new technology. I like the positive criticism. Honda's FCX with the solar powered water-to-hydrogen fueling station is the shit. Anyways, couldn't help but comment with my (worthless)opinion. peace, zach

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