Featured Mazda e-TPV to have Wankel dual fuel range extender

That’s really cool!

Wonder how the window sticker stacks up?

 

They did this back in 2007 with a Premacy(Mazda5). Well that was just a series hybrid, the battery wasn't big enough for EVing on just it, let alone work for a plug in. It may have had a plug, but I think that is in error. But it had a rotary and was dual fuel gasoline and hydrogen. It never got out of Japan, but the RX-8 dual fuel was available in Norway.
Mazda Premacy Hydrogen RE Hybrid - Wikipedia

If you are going to burn hydrogen in an ICE, a Wankel might be the best choice. Pre-ignition of the fuel is less likely in it for one reason. There are a couple others mentioned in a video at this link.
If you are going to burn hydrogen in an ICE, a Wankel might be the best choice.

In the non-hybrid RX-8 and BMW Hydrogen 7, using hydrogen meant a large cut back in power output(Mazda), or putting FSPs to shame in the fuel sucking(BMW). As a series hybrid, it sounded like the Premacy didn't suffer the power loss, but I could not find fuel economy numbers for it on the two fuels.

 

Given where I live, I’d only ever be able to feed it gasoline. But I reckon it’s a neat variation on the PHEV.

 

We may see a gasoline only variation down the line. At least those in California will.

 

From the link -

Hmm. The RX-8 dual fuel hydrogen car could only provide 100 km of range on hydrogen and the tank took up the entire trunk. Pressure is doubled but that would be what 200 km on the easy japanese test, maybe 80 miles on the EPA? Or perhaps they will add bigger tanks.

The latest guestimates I've heard is that if you are going build 10,000 psi tanks (700 bar) and related hardware to carry 5.6 kg of hydrogen costs may come down to $2000 per vehicle if you put them in 500,000 vehicles a year. Current world wide production is around 3500 vehicles a year and toyota may have costs down to around $6000/car as it has the highest production. This seems like a big waste of money and space if you aren't going to fill them and use them. Lets say a rotary hydrogen in that phev set up gets 40 mpge (the rx-8 was much worse) and 5 kg is usable then you are talking 200 mile range after taking up a lot more space than the trunk of the rx-8. At that same 500,000 vehicles a year why not use a 80 kw fuel cell which likely would be around $5K at those volumes and would be more efficient and not need nox after treatment. That rotary may be lighter and cheaper than a piston engine for hydrogen, but its not going to be as efficient as a fuel cell.

Flex fuel phev with 35.5 kwh battery? Sure that may make sense, and you could grab 3 cylinders of of mazda's 2L skyactiv-x or toyota's 2L dynamic force which may be slightly less efficient but proven in the real world. Fuel it with renewable methanol, and carbon footprint would be lower than hydrogen unless you greenwash it. That flex fuel engine and fuel tank would also weigh less, cost less, and be more reliable when including the cost of unsubsidized fueling. There is no reason a 1.5L 3 cylinder version of either of those extremely efficient engines would not be able to get around 50 mpge on methanol, ethanol, or gasoline (in any blend) on the highway. The 35.5 kwh battery should be able to provide fantastic city efficiency despite the higher weight.

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Mazda is a small Japanese car company. The Japan government is pushing hydrogen cars. Mazda didn't have the resources to developed more advanced engines and transmissions, and hybrids. Depending on Mazda leadership's views, a bi-fuel ICE car was the best they could do to support, or play along with, their government's hydrogen policy. They started this hydrogen/gasoline rotary project while Ford still had a large say in their operations. Partnering with Toyota or Honda for fuel cells wasn't option then.

A bi-fuel ICE is a more pragmatic approach than a PEM fuel cell. It acknowledges that hydrogen refueling infrastructure will take time to build, and it is easier to sell a car that isn't 100% dependent on it during that time. I disagree with using hydrogen for car fuel, but if that is the accepted goal, starting with hydrogen ICE is a good place to start building support. The fuel system will increase the car's price, but it is cheaper than also adding a fuel cell and battery while swapping the established ICE drive train to an EV one.

The 35.5kWh battery should be good for 125 to 150 miles of EV range. Plenty for most day to day uses. Add a range extender without the hydrogen silliness, and this could work for a lot of people. A rotary might have better packaging and NVH than a 3 cylinder. The A3 E-tron PHEV one was just 0.25L. We won't get any details on the engine until the production model is unveiled at the Tokyo Motor Show. InsideEVs is reporting that what was shown were prototypes built on the CX-30, they may have even been using ICEs from that model.
Mazda's First Electric Car Does Not Believe In Large Batteries
Plus a few more hints on the production model here.
We drive Mazda's first-ever electric vehicle | Stuff.co.nz

It is using a BEV platform, FWD that can be enlarged for larger models with possible RWD and AWD in the future.
The rotary isn't a one off. In addition to the EREV/REx, Mazda is planning a PHEV and series hybrid around it. What gets delivered will be market dependent.


What those articles, and two others, didn't mention was hydrogen. I can see Mazda offerring a bi-fuel version in those markets that have hydrogen available, they have already developed rotaries for that purpose, but I'm guessing that wasn't Mazda's main push with the presentation.

 

I really thought the poor fuel economy of the rotary mazda and the bmw ice hydrogen cars showed that you would need rather large tanks for decent range. Since this is a range extended phev, it requires a full electric drivetrain. It seems like a big complication to have BEV + liquid fuel tank and high pressure hydrogen tank plumbing. Mazda in the skyactiv-x (available in europe this fall) has one of the most advanced efficient engines.

Well audi built the prototype with a rotary then thought better about it. There is no denying that rotaries can not produce the efficiency of a modern efficient atkinson or miller cycle valved normal ice. Hydrogen does solve the problem of unburnt fuel, as leaking hydrogen does not cause pollution, but if its going to be bifuel then you need to have better pollution control for the unburnt hydrocarbons, and the NOx. Produce that hydrogen only rotary and who knows, you may get closer to mazda or toyota's efficient engines but not if you are going bifuel. In 2012 mazda told us they were making that rotary much more efficient, but no numbers have come out in the 7 years since that announcement.

My guess is they will have some built for hydrogen, some built for flex liquid fuels, and a few prototypes that are bifuel. Perhaps mazda will figure out how to do a ever phev better than the bmw i3 and will sell it decently. They will sell some hydrogen versions to governments like they did their rx-8. No need for trunk room. Hopefully they buy some cheap hydrogen tanks from toyota. I don't think rotary nvh is going to matter to potential customers.

 

Did you read the article? They’ve specifically made the claim that a rotary engine operated at fixed RPM can be more efficient than a piston engine. They acknowledged that rotary engines in automotive use typically used more fuel than piston-powered competitors, but writes it off to the dynamics of variable throttle operation.

Now, they need to actually prove this… but the way I’m looking at it, they’ve got a fluffy nice message with the hydrogen thing, and a practical range extender generator that doesn’t depend on that hydrogen fuel system- they could go into immediate production on the gas setup, big scale.

If the constant-throttle claim actually holds up, there’s officially another way to skin the PHEV cat.

 

Well it just is every rotary mazda has ever made is less efficient than their equivalent ice if you build an engine for a smaller power and rpm range you can make it more efficient. For gasoline the highest compression a rotary has been able to be made has a compression of 10:1. Beyond that seals have trouble.

Now a hydrogen only rotary could be more efficient, but then that bi fuel will probably kill it.

Sure absolutely. I read it, and don't believe it based on previous mazda promises and delivery. Show me the trifuel than the phev on gas and then I will believe.

Mazda says they have applied skyactiv-x tech to the rotary. There first skyactiv-x 4 cylinder supercharged engines will arrive in europe later this year. I can see some of this tech making the engine more effiecient than previous rotaries, but they still have to overcome the compression problem of rotaries to get to the same efficiencies. Say the more normal ice is 43% efficient, if the rotary is 38% efficient that is probably good enough. I can't see it having that efficiency on both gasoline and hydrogen though. I say bring it and prove it. For most of the world having those big hydrogen tanks and little infrastructure to fuel them makes a tri fuel phev for of a curiosity than a ground breaking car.

gm thought about doing this then rejected as did audi. you can do the trick without making it a rotary or burning hydrogen. To me saying it can burn hydrogen too is more a gimick than a feature.

 

I ain't defending hydrogen. I just understand why a car company without a fuel cell department would turn to ICE for using it when facing pressure to do so.

Where to put the fuel tanks is a question all bi-fuels face; hydrogen just makes the answer harder.

Audi had twenty prototypes of that A3 running around with a rotary. Even the designers admitted that a rotary wasn't likely to make it into a production model, but it was most likely the Recession that killed it than what ICE was running the genset. But this is Mazda, who has actually sold rotary engines in real cars. Their SkyActiv suite shows they have the expertise to make this work if possible. I knd of doubt the SkyActiv-X claims, so can wait and see for both.

We are talking about a large battery PHEV. Engine efficiency may not be the main priority. Packaging is an issue that can't ignored. Considering how Prime drivers here cry about the engine firing up, NVH may be more important on a PHEV.

Hydrogen wasn't even a footnote in other articles. I think the OP article latched onto it to further his anti-Tesla screed.

I agree Mazda will have a few hydrogen ones available, as they did in the past, but it might be less important to them than the Clarity FCEV is to Honda. I think Mazda will just be happy selling rotaries no matter what the fuel is.

 

Statement here that the new rotary can meet US emission regulations.
Mazda confirms flexible 'XEV' electric rotary driveline | Drive Car News

This is just a nice overview of the Wankel.
Mazda Might Actually Be Onto Something | CleanTechnica

One of those two mention the rotary on the PHEV could be fueled by propane for electric generation. I'm not expecting that to make it to a production model.

 

Next month at the Tokyo Motor Show...

First Mazda battery-electric vehicle will go on sale next year | Autoblog

 

I've dreamed about a concept like this for years. Like the BMW I3 but better. You can design the ICE differently when it is only being used as a generator. I've been following this company Liquid Piston, they have a rotary engine (not a wankel) that can run Otto, Atkinson, Diesel cycle or a new type of HCCI they have developed. They also mention water injection for waste heat recovery and engine cooling which is awesome. I know there's been lot's of companies like this, but they've been at it for a while and have some real progress to show which gives me hope; but I'm not holding my breath!

 

Hmm, when ever I’ve found metrics for dual fuel hydrogen car the numbers have been pretty scary.

I’ve often wondered why it couldn’t just be dual fuel hydrogen/ cng in the case of an oil burner, you could use the same tank for either.

 

I must say, I am extremely interested in this vehicle. The rotary range extender looks to be the killer feature.

• Rotary engines are small and light...but I'm skeptical of the efficiency. However, the fact that it will run as a generator can be taken as a huge engineering advantage and hopefully will benefit in terms of efficiency.
• The fact it is dual fuel is a win/win. However, I expect most will use gasoline for quite some time.
• Hopefully Mazda has done their homework on battery longevity. I'd wager they will as Mazda has a pretty darn good engineering pedigree.
• I like Mazda. We have had three of them before moving to Toyota...but swore them off due to horrible rust problems. In theory, Mazda has 'solved' their rust issue...but time will tell.
• The EV-plus-extender design is interesting. It will be fun to see how it fares against the competition.

 

On the initial announcement, I though the Volt was going to be like the i3 but better.

Started a thread about LiquidPiston here, It's not a Wankel | PriusChat

Years ago, I saw a piece about a 6 cycle piston engine. The added cycles ran on water injection and the resulting steam. It claimed weight savings in not needing a cooling system. WW2 planes and some cars used water injection, referred to as methanol injection, but the alcohol was really just there as antifreeze.

Yeah, I had posted them somewhere else just before this was posted here.
The RX-8 lost nearly a hundred horsepower when running on hydrogen, and the BMW Hydrogen 7 had a MPG figure that would make Hummers blush. Though I think the Hummer had a better rating even when it was on gasoline.

Technically, that would be a flex fuel. While it sounds simple, it would probably be hard to execute.

CNG cars store it at 3500psi. Hydrogen car tanks are at 10k psi. CNG could only be added to a tank below 3500psi; you'd have to run most of the hydrogen out before adding it. Then what happens when you add hydrogen on top of CNG. Is it safe to compress methane to that pressure? I think it is supercritical at that point. Then hydrogen is weird; it heats up as it expands. There is no initial cooling of the NG in the tank when hydrogen is added beyond whatever the hydrogen was chilled to. Keep hydrogen pressure in the tank to 3500psi, and the car will have poor range with it.

The car would still need two fill ports.

The linked article in the OP was the only one that I've seen that mentions hydrogen in connection to this new PHEV, and the author might be speculating about it being dual fuel. Another article mentioned Mazda designed the genset to be able to run on propane for stationary generator duty. So what exactly the production car can do is unknown at this point.

Mazda has been playing around with hydrogen rotaries for awhile now. Turns out hydrogen is a better fuel for Wankels than gasoline. I expect a hydrogen fueled version of this being available in Japan, Norway, Southern California, etc.; places pushing hydrogen. I don't see it being dual fuel though. Their past models that were the RX-8 and Premacy(Mazda5). The RX basically lost the trunk to the hydrogen tank. The Premacy has more space to lose, but it was just a hybrid.

This new car will have a battery somewhere between the Ioniq Electric and Leaf in capacity, so it is likely the same with size. Adding both a gasoline and hydrogen tank will require compromise in space or range on either of those fuels. I think hydrogen will be the only fuel for the range extender, and that car will be a compliance one. Everybody else will just get a gas tank.

 

That is what I'm thinking...if anything, it will be either a hydrogen OR a gasoline fuel tank...not both. And that seems to be a pretty smart move because it gives them options for a compliance version as well as a mainstream version without much modification other than a new tank.

 

Mazda does already have skyactiv X which would be delivered in Europe later this year. That engine in 2 liter 176 hp that can often run in HCCI mode but needs to initiate with spark and runs in otto and miller cycle (forced induction version of atkinson) where appropriate. To get to HCCI it needs forced induction, in the case of the mazda 3 it comes from a mechanical supercharger, but in a phev it likely would have an electronic supercharger or an electronic assisted turbo charger (expensive version in mercedes project one, inexpensive version has a turbo and electronic supercharger where supercharger only needs to be powered at rare times to spool up the turbo with exhaust). The diesel cycle really is compression ignition, the skyactiv X does this in an efficient lean burn mode but initiated with spark plugs. Lets consider that a 3 cylinder version with a small electric supercharger and small turbo should weigh less than 300 lbs and require less pollution control afterwards, on a 3000lb+ phev I doubt the weight is a factor. It will be bigger than a rotary and noisier because of hcci, but more efficient over a large range of power and torque. My guess you could get to 50% efficiency while in homogeneous charge lean burn mode.

A 3 cylinder 1.5L version of toyota's dynamic force Atkinson engine would provide about 100 hp, and could be made less expensively if it just needed to provide power in a smaller band, and we know it would be 41% efficient.

Now a rotary will weigh less and perhaps cost less while having better nvh characteristics but if mazda actually had one more efficient than their current engines they would have actually demoed one. I believe they have gotten more efficient than the rx-8 engine, but it is doubtful because of inherent design problems they can get as efficient as toyota's dynamic force let alone skyactiv-x.

Now liquid piston has got $6M from darpa to design rotary generators. They have changed the rotary design to allow for higher compression, and it shows promise. Perhaps My guess is it needs at least 5 years more development before it is suitable for a car.

A low cost 3 cylinder efficient engine probably is probably the best idea for a phev. The 2 cylinder in the i3 was too noisy and underpowered. Mazda really wants to use the rotary because engineers have been working on it, but its not going to be better than the engines in the clarity phev or prius prime in terms of efficiency once the battery is used up.

 

There was a thread around here somewhere regarding the new Mazda rotary engine. The speculation is that this is the one that will go into the electric vehicle. Apparently Mazda has been working on it for a long time and seems to have perfected it for use as a generator.