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Subaru, Toyota, and Mazda commit to new engine development for the electrification era, toward carbon neutrality

Subaru, Toyota Motor and Mazda Motor have each committed to developing new engines tailored to electrification and the pursuit of carbon neutrality. With these engines, each of the three companies will aim to optimize integration with motors, batteries, and other electric drive units.

While transforming vehicle packaging with more compact engines, these efforts will also decarbonize ICEs by making them compatible with various carbon-neutral (CN) fuels. (Earlier post.)

In pursuing decarbonization, all three companies have focused on carbon as the enemy. Under the extreme conditions of racing, the companies have worked to broaden powertrain and fuel options by competing with vehicles running on liquid hydrogen and CN fuels.


This process has clarified the role that future engines will play in achieving carbon neutrality. With the next generation of engines, the three companies will seek to not only improve standalone engine performance but also optimize their integration with electric drive units, harnessing the advantages of each.

While being highly efficient and powerful, the new engines will also revolutionize vehicle packaging by being more compact than existing models. Smaller engines will allow for even lower hoods, improving design possibilities and aerodynamic performance while contributing to better fuel efficiency. The development will also emphasize compliance with increasingly strict emissions regulations.

At the same time, the new engines will be made carbon neutral by shifting away from fossil fuels and offering compatibility with various alternatives, including e-fuel (synthetic fuel), biofuels, and liquid hydrogen. In doing so, these engines will contribute to the broader adoption of CN fuels.



That's nice 20th century thinking. Now start making cheap batteries at scale in the 21st century.


@Nocreditreports That's very progressive of you. Too bad the real world isn't actually ready for that.

Resources, infrastructure, technology unknowns, etc. aren't ready for mass EV adoption like you're probably hoping for. These companies, Toyota in particular, are able to see that and have been proven right so far.

I drive a lot of vehicles. Many of them EVs. Guess what? Charging is a huge pain in the a$$. Chargers are often full, not working, or working at such a slow rate that they're basically useless. Home charging doesn't work for a large portion of the population (most of the U.S., in fact). And we have no idea how long batteries will actually last. Nevermine promised EPA ranges versus the actual real-world range that's usually far lower.

EVs are nice and all, but the reality is that they are not ready for the mainstream in the U.S., rural China, much of Europe, and many other locations. Big markets. Not podunks like the Netherlands or other small population, high-income areas.


Mac is right, you will never beat the energy density and flow rate in megajoules per minute of liquid fuels physics says so and math is universal. Hydrogen is also not a panacea it's hard to store,leaks everywhere and tends to do nasty things at a few percentage in air and enclosed spaces...think a home garage and a venting LH2 tank.

Efuels hold promise they can be identical in chemical comp and density to liquid fuels already in use or they can be alcohols which have high octane numbers. In that case you can go to 16:1 compression ratios and get into the 50% BSFC area over a large operating window. This is fuel cell performance with ICE levels of cheapness. The ideal set up for most of the USA is going to be a hybrid with a fully electric drivetrain and a small high eff generator running at its peak eff point to charge the smaller onboard pack. For most commuters this means a 100 mile pack and a one liter or so range extender. Most commutes are 40 miles round trip or less. This means a 100 mile pack with the a.c. Roaring in summer heat is 50% DOD by the time you get home. LFP cells can take 10000+ cycles of 50% DOD at 1C or less. L2 charge it at home or work at 1C and it's three hours to put in 50 miles range. The range extender running on biofuels or efuels such as ethanol can hit 50% eff it's some job is to come on at 20-30% DOD and either keep the pack at that level of charge while at freeway speeds this would take 20kw for a model S sized car or push charge in at freeway speeds in that case 50kw would push 1C into 100mile pack. After an hour of running your pack is full again and the little one liter engine can turn off again. Given that most high compression engines have a broad range of torque and 40+% BSFC range you can tailor the engine to run at three points. Charge sustain at suburban speeds(50mph) this is 11kw , charge sustain at freeway speeds (75mph) 22kw , charge push at freeway speeds 50+kw. At speeds in the 25 to 30 mph range in urban areas you use only the pack and if needed run the extender at peak eff once every few hours to bring the pack up to 80% or so then cycle off.

Roger Pham

Great, exactly as I have been suggesting for a long time. A small engine 750cc to 1-liter, 2 cylinder, 75 hp to 100 hp is sufficient. Keep the engine simple. Can run on biomethane, biomethanol, or hydrogen. A small battery pack of 12 to 15 kWh is sufficient for daily commuting. Keep the vehicle light and inexpensive. PHEVs today have too big and complicated engines and that is why they are expensive and heavy.


There's some over-simplification here.
Sure, liquid fuels are more dense, but you need 4-10x as much energy content in order to get the same amount of performance. Plus you need a gas tank, engine, transmission, etc. Size-wise it works-out in favour of batteries in most cases.

I'm not sure why people think that home charging is impossible for most of the US. It's a country of single-family homes. Home charging doesn't have to draw more power than air conditioning (which is ubiquitous). Granted, most homeowners will need to run a new circuit to their garage/driveway, which isn't free, but it's a one-time cost.

It's great to do the maths to "prove" that a range extender hardly needs to run at all, but the same maths also prove that you don't need to charge very often. The average commuter might only need to charge once a week, and said charging will happen off-peak while they sleep. It hardly seems worthwhile to carry a heavy, expensive range-extended everywhere you go in order to avoid plugging a cord into a socket once a week. Don't forget that you have to drive to a gas station, which is more of an inconvenience than doing something that takes a few seconds in your own driveway.


For most applications, the requirement of energy dense liquid fuels is not necessary.
Aviation and Maritime applications are definitely some of those that require energy dense liquid fuels and currently, best handled by hydrocarbon based fuels.

Actually a Range Extended EV may not need an ICE and could include an additional battery that does not have the cycle life of an LFP or Sodium Ion battery, i.e. greater than 4,000 cycles. It would have a high energy density (>500 Wh/kg) so the extender battery would weigh less than 100kg and used only 20% of the time.

There is another group of applications that do not require energy dense fuels, however, would require a large battery and long recharging times. Long Haul Trucking and Diesel Rail are some examples. This is where Hydrogen may be used.
Though, Compressed or Liquified H2 has problems with infrastructure costs and poor volumetric energy density. Liquid Organic Hydrogen Carrier (LOHC) is an option that would not require infrastructure changes and could use existing retail fuel distribution, providing a cost-effective way to transport hydrogen energy.
Companies like Honeywell, Enzo’s, and Chiyoda are investing in this approach.

However, this approach incurs ∼ 50% energy loss from the endothermic dehydrogenation and compression of hydrogen. MIT has proposed an alternative concept based on onboard hydrogen release, where the hot exhaust from the hydrogen combustion engine is used to partially power the endothermic dehydrogenation.



Your suggestion for a serial hybrid is brilliant but it isn’t new. I believe Popular Mechanics or Popular Science proposed something similar in the 1970s. After years of design, testing, refinement, validation, emissions testing, regulatory approval, Nissan brought a petrol serial hybrid to market in 2020. Their e-POWER Note is what this group wants to re-invent with the twist of CN fuel. I think that is great. It will give ICE heads something positive to work on even if odds are overwhelming that nothing will come of it. Designing an engine for this should be trivial though time consuming. The hard part will be getting a commitment to build and use their designs. An even harder lift will be getting someone to commit to building out CN fuel production capacity. Batteries and Fuel cells have years to go before anything tangible is likely to come from this.

Roger Pham

Hi Bernard,
Please understand that charging an EV would make the most sense when there is a surplus of Renewable Energy in the grid. If the grid depends on fossil fuel to generate electricity during the moment when solar and wind is insufficient, then it would be better to use Carbon Neutral (CN) fuel in the PHEV at that moment. Also, when the grid is over burdened with maximum demand, then the PHEVs have the option to save the grid by running on its own power plant. This would save about $800 Billion in capital investment to upgrade the grid if 100% of vehicles are full BEVs.

By taking out 80% of the battery capacity of a BEV, the weight, cost, and space savings can more than justify a small 2-cylinder engine. No transmission is needed because it just produces electricity using its starter/motor/generator all combined into 1. In this manner, 1 battery pack from a full BEV can serve 5 PHEVs.
Having no capability to charge an EV at home can be solved by charging at work, from solar PV panels. During rainy days, the EV can be powered by its engine and CN fuel on board.


@ Roger Pham:
It all depends on the individual necessities. E.g. since my retirement, I don't travel long distances anymore; for the 10,000 miles p. A. that I accumulate, my EV is more than satisfactory.
Additionally, the PV system on the top of my roof supplies 95% of my total energy consumption which includes a heat pump for heating and hot water supply plus charging my EV from my own Wallbox. I have yet to drive a single mile beyond what my own Wallbox has delivered.
Two things that I truly miss are range anxiety and a dense charging system.
If you really want to know what a pleasure it is to be independent of some greedy hawks, then let me know and I'll inform you.



If the problem is the grid, then let's fix the grid. Good news: that's already happening!

Hybrids have notoriously poor space utilization. Compare a Prius to a Corolla for instance: they are the same size on the outside, but the Prius has much worse trunk space. Any similar-sized EV puts both to shame, of course.

In other words, your "solution" of building-out more liquid fuel capacity means that everybody has to move-up a size class, which is very wasteful. They also need to pay much more than they would otherwise, including the current cost of EVs.

Why pay more to get less? Why create new infrastructure for toxic liquid fuels when a better solution is already available?


PG&E provides electricity to the geographic northern 2/3 of California and is the world’s largest IOU. In 2023 100% of the electricity they provided to customers was carbon free.

The adoption rate of EVs in Northern California has been about 10x what it is in the US excluding California.

Their CN efforts are welcome but would be most appropriately focused on long haul heavy transport and/or marine and aviation transport where they have a better chance of finding a niche.

Roger Pham

@Yoatmon, Bernard, Gryf, Gasbag, et al,
Incidentally, Geely and BYD recently came up with a car engine capable of 46% thermal efficiency when function as a range extender, for a PHEV with total range of 2,000 km or 1,250 mi range. This kind of efficiency rival thermal power plants and would make it more efficient and less costly for your PHEV to use its engine and Carbon Neutral (CN) fuel when the grid is deficient in Renewable Energy (RE), because electricity from the power plants must incur losses from transmission, distribution, and charging, while power from the PHEV's engine can be transmitted directly to the wheels. during cruise.

A 1,250-mi PHEV can generate electricity for long time to back up the grid during times of disasters with prolonged power outage from the grid. Natural disasters are increasingly common due to climate change and so are the frequency and duration of power outages. Where I stay, we recently suffered from power outage for TWO freaking days as the result of a very powerful storms that knocked out a lot of trees and power lines. For a PHEV designed to provide power backup for home and small businesses, this kind of power outage would be much more tolerable.

When going on a camping trip or doing contracting works in remote areas, the ability to provide extended electricity for the camp, including for portable A/C, lighting, and other power tools would be extremely valuable, and only long-range PHEVs can fulfill this kind of role.

CN fuels can be dispensed in existing gas stations, only needing compatible storage tanks and pumps... at a lot lower expenses than building out more Supercharging stations. Furthermore, PHEVs only consume 1/5 to 1/10 the fuel consumption of a compatible gas-only vehicles, so the added expense of compatible storage tanks and pumps would be much less than for fueling a fleet of comparable gas-only vehicles.

The trunk space of a PHEV can be made comparable to that of a comparable gas-only car when the engine in the PHEV can be downsized to 1/2 - 1/3 that of the gas-only car. Imagine having the engine, e-motor, inverter AND even the spare tire and other accessories adjacent to the downsized engine... in the front under the hood, with the battery pack under the front seats, and the gas tank under the rear seat, then the whole rear trunks space will be comparable to that of a gas car. Nothing to it!


Roger I agree on your hybrid point of view however there are perceptions when it comes to marketing automobiles the customer wants a car that can do everything all the time everywhere and cost as little as possible hence you're not going to sell a whole lot of small cars that work in urban Suburban settings it's just the way it is it's a mindset

Roger Pham

Totally agree, SJC. Small cars won't sell well in N. America. That's why the Tesla Model 2 is DOA (Dead On Arrival) because it is too small, and likely the 2-seat Robotaxi as well.

The Tesla CyberTruck (CT) is also DOA because it is lacking an engine range extender and therefore not selling well, neither. A range extender doesn't have to be big, just enough to supply average power required for normal cruising, which is about 30 hp for vehicle the size of the CT,, so a 2-cylinder 750-cc motorcycle engine with 75 hp is enough, even for occasional towing when the power requirement can double. For frequent towing, a 2-cylinder 1-liter 100-hp range extender would be more durable. The e-motor is always standing by to supply for acceleration and climbing. The PHEVs can do everything all the time and can travel everywhere, perfect for all type of demands and all types of customers.
The full BEVs are deficient and hence are not selling well anymore.


The US is just a fairly small part of the world car market and will not determine its direction.
In other areas the advantages of relatively small care not oversized to do the job are starting to be more widely recognised, so for instance in France, which of course in itself is yet smaller but where conditions are more typical of the wider world, taxation according to size is starting to be introduced.


Roger, the lack of a range extender is the least of the Cybertruck's problems. It probably doesn't even make the list.
You probably already know that Tesla's Model 3 and Model Y out-sell almost everything else in their segments in the US, despite the "lack" of gasoline engines, gas tanks, exhaust systems, and all those other things you think are necessary.

Roger Pham

Bernard stated:
"...the lack of a range extender is the least of the Cybertruck's problems..."
Reply: Oh yeah? Then why Ford is halting the production of the BEV Lightning PU truck, and shift production toward PHEV trucks? Why is BYD offering the hot-selling Shark PHEV PU truck world-wide? Tesla is missing out big time for this omission.

"You probably already know that Tesla's Model 3 and Model Y out-sell almost everything else in their segments in the US, despite the "lack" of gasoline engines, gas tanks, exhaust systems, and all those other things you think are necessary."

Reply: That was then...For NOW, please look at the rapidly increasing sales of BYD's PHEVs and the stagnating sales of BYD's BEVs. Time have change, and companies must adapt to stay in business.
How hard is it to put in a 2-cylinder 1-liter range extender in the Cybertruck, so that you can pull trailer all day long without having to stop 1-2 hrs for Supercharging every 1:30 hr of driving? People are using PU trucks to pull huge RVs to enjoy vacationing across the continent, or big boats to travel several hundred miles to catch the big fish...they ain't gonna wait for 2 hours to supercharge every 1:30 hr of driving.

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