By on October 31, 2016

2015 BMW i3 Range Extender Refueling

Despite paying lip service to the growing — but still minuscule — electric vehicle market, automakers do love piston engines. The companies that built their current empires around internal combustion engines take comfort in the technology, finding stability and solace in the seemingly timeless act of burning fuel in exchange for power.

Batteries and electric motors? We understand those too, the companies claim. It’s not a new thing, after all.

What automakers don’t particularly trust is a new type of engine that could squeeze record mileage out of a tank of gas, for less cost, while still using a moving piston with fuel injectors, intake valves and exhaust valves.

An Israeli company claims it could double the range of vehicles for little cost, if only automakers would adopt its technology. According to Agence France-Presse (via, the Tel Aviv-based Aquaris Engines is in talks with Renault after developing a horizontally oriented single-piston combustion engine that does away with all the hardware one normally sees below the piston head.

No crankshaft or flywheel. No mechanical connection to the drive wheels. Just power produced twice as efficiently as a conventional engine thanks to a “free” piston system.

“It is the highest efficiency you will probably meet,” Aquarius co-founder Gal Fridman told AFP. “It has the lowest emissions and the highest power-to-weight ratio.”

The engine Fridman describes sounds an awful lot like a version of the free piston engine “linear generator” under development by Toyota. Word first leaked out about that automaker’s efforts two years ago. Featuring a magnet-wrapped piston connected to a gas spring chamber, the piston generates electric current by moving up and down inside a linear coil. Powering the piston is a simple two-stroke combustion chamber with associated fuel delivery and exhaust hardware.

Used in a plug-in hybrid vehicle, the unit would be a simpler alternative to the repurposed multi-cylinder engines that currently act as generators. The unit’s lighter weight, longer range, and lower cost could give automakers a leg up on their plug-in competitors. There’s also a chance that, if used en masse, the technology could stave off the need for automakers to invest in expensive battery electric vehicles.

Of course, this assumes the engine works as designed, with no drawbacks. Aquarius says it does, with the company currently seeking a third round of funding (to the tune of $40 or $50 million). It’s also in talks with French automaker Renault, which confirmed the conversations without mentioning any “obligation or a specific project.”

While Renault seems to have at least a mild interest in Aquarius’ engine technology, don’t expect a revolution in the industry — at least not for a long time, even if the free piston design becomes accepted as a reliable generator.

John German, senior fellow at the International Council on Clean Transportation, told AFP that the generator’s “radical” design — as well as the changes needed to install the technology — could prompt cautious automakers to stick with what they know, and what they already manufacture.

Ana Nicholls of the Economist Intelligence Unit claims a widespread adoption of the generator design isn’t likely. The industry shift is from gasoline-powered vehicles to pure electric vehicles, she said, and automakers aren’t likely to tap into R&D budgets to test unproven technology.

For Fridman, the predicted electric car revolution is more hype than anything else.

“A lot depends on the path the electric vehicle revolution takes,” he said. “If pure battery electrics sell well then there probably isn’t much need for this kind of engine. But if people balk at the long recharge time and high costs of battery-only cars, then systems like these might be the future.”

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39 Comments on “Low-Cost Piston Engine of the Future Could Be Doomed by Lack of Interest...”

  • avatar

    If it ACTUALLY works and is cost-effective, it will be built.
    If not, then not.

  • avatar

    “prompt cautious automakers to stick with what they know, and what they already manufacture” = More R&D, less profits, so not going to happen unless the EPA raises MPG standards again. OR oil goes back to $120 a barrel and there is a consumer out cry.

  • avatar

    If this works…

    It’s an amazing piece of lateral thinking.

    It also has potential to replace the technology in gas and diesel generators and every application those are used such as locomotives, marine and heavy equipment. How about a gas/electric chainsaw?

    • 0 avatar

      Don’t forget ultralight and light aircraft, but just the engine, without the battery/motor part. Besides having a high power-to-weight ratio, they also have a small form factor, allowing for a smaller, more sleek engine nacelle.

      This concept is not new, as heavy handle said. About 11 years ago, I invested a small amount in an engine called the Dyna-Rev. I am not sure if was a free piston design, or something like a wankel; really couldn’t tell from the drawings. But it was the same concept — a lightweight, single piston design that did away with connecting rods, and resulted in small package and a high power-to-weight ratio.

      They initially planned to sell it to Caterpillar, Mercedes or some other auto maker. Then, around 2007 or so, they decided to finish developing of the engine on their own. They got up to at least a third, maybe a fourth prototype.

      I told my family and others that were interested in investing in the project that they would have to get it to run on a test stand for at least several thousand hours without failure before anyone would take them seriously (like JimZ said.) They got it to run, but I don’t know if they got it to run for any length of time. I told them also that anytime you invest in something like this, it needs to be money you can kiss goodbye, because that will be a likely outcome, though the payback if it does work will be great.

      I thought 2013-2015, when fuel prices were high, and everyone was developing their own hybrid vehicles, was the peak time for this project to make it big. Now that gas prices have fallen, battery technology continues to improve, and others like Aquaris try their hand as well, their chances of making it commercially grow dimmer.

      But this concept is not new.

      • 0 avatar

        Absent coils and the rest of the package to get electricity from the free piston moving, I’m not really sure if the engine makes any sense at all without a mechanical linkage/conrod.

        I’ve seen drawings of similar “ideas.” With twin heads at opposing ends playing powerstroke ping pong with the piston, resulting in two effective “cylinders” sharing the same bore. But hose all had mechanical connectors on the side or ends of the piston, and were really meant to game racing reg engine size rules, rather than be even remotely practical for general use.

        Getting rid of the, in practice impossible to seal efficiently, mechanical connectors entirely, in favor of pure electricity output, is pretty ingenious, and at least sounds plausible. Like the turntable industry before them, the manufacturers may come to realize a moving coil design is more efficient than a moving magnet one, but who knows. It’s really best though of as a form of mechanical petroleum fuel cell, though, rather than an “engine.”

  • avatar
    Arthur Dailey

    Who here believes that the oil industry executives or OPEC will purchase all the rights and patents to this technology and then store it in some hidden chamber with Bigfoot, the aliens from Roswell, those who actually shot JFK, The Ark of the Covenant and the 100 mile per gallon carburetor?

    • 0 avatar

      Dont fret. They will be along shortly claiming 9/11 was an inside job and various mass shootings are staged by the gub’a’mint to eliminate the 2nd amendment and anybody who disagrees is a sheeple that has breathed in too much of those vapor trails left by militany aircraft.

    • 0 avatar

      If oil were in the ascendancy, it might be plausible for a movie plot.

      But there’s such government mandated pressure away from oil that something like this could save their bacon. Electrics, LNG, hydrogen all have the problem of installing refueling infrastructure from scratch; oil doesn’t. If anything, I would expect oil companies to jump on this and subsidize its first installation in a mass production car, because if they could show doubled efficiency, it would take a lot of wind out of electric’s sails. All that lobbying, blaming oil for pollution, false claims of peak oil, etc — poof! like a sucker punch.

      Seriously, if the choice is a huge loss of sales to electrics or half sales due to more efficiency, half sales could be very enticing. Of course, this is all over several decades, not just the next 5 or 10 years.

      • 0 avatar

        That is one way of looking at it I did not think about. I think the ship already sailed for a automobile or other manufacturer to pick his technology up once oil prices fell and most developed their own hybrids, but as a means of keeping oil competitive with other emerging energy sources is another possibility.

      • 0 avatar

        If this works, it could benefit everyone: oil and greenies alike.

        Think about it. We know that a short-range EV handles 80-90% of the typical driver’s needs, but they won’t buy one because of a) cost b) charge times and c) range anxiety. A Chevy Volt solves b) and c) but not a). But suppose this little gas generator made the likes of the Chevy Volt considerably cheaper to build. Simpler, cheaper engine. Simpler, cheaper transmission: no mechanical connection to the engine, just a direct drive EV motor and some wires between the battery and generator. Smaller and lighter for easier packaging and less weight, which in turn means you don’t have to buy quite as much battery. Volts for all, in all manner of body styles and sizes!

        Gasoline wouldn’t become obsolete, which obviously helps those in that business. But it would also be way easier to get the public to drive EV for most of their miles, without having to first massively scale up fast-charge infrastructure or massively reduce battery cost.

        You’d get most of the benefits of a full EV transition, but much sooner, by overcoming practical and psychological barriers. I’m all for less polluted cities and sending less of my money to Saudis who want to learn how to fly planes but not how to land them. Who’s with me?

    • 0 avatar

      Just hope they don’t target you and you find yourself on one of the new FEMA prison trains to some unused military base in the middle of nowhere!

  • avatar

    I’m not buying claims of doubled efficiency. I know that the traditional 4-cycle ICE isn’t the most efficient possible design, but these guys are claiming a doubling? And that’s AFTER the conversion from mechanical into electrical and back into mechanical energy?

    Color me skeptical.

  • avatar
    heavy handle

    Free piston designs aren’t a new thing. The problem with every single one yet is over-promising and under-delivering.
    Come to think of it, that’s almost exactly the same situation as claims of revolutionary new battery technologies.

    It’s a play to get investors. The odds of seeing an actual working product are very low, based on past performance.

  • avatar

    What is that oh-so-cab-forwardy car in the photo?!

    Is there a hint of roundel in that hubcap/button?

  • avatar
    Big Al from Oz

    I like this. It’s an extension of how an electric motor can be used as a generator. Except this is a solenoid.

  • avatar

    History is littered with novel internal combustion engine designs which worked “great” in a lab setting, but faltered when challenged with working great for 200,000 miles and 10+ years.

    and as always, people sit there and bicker over *peak* efficiency numbers when the average car/truck engine is almost never running at or near peak efficiency.

    • 0 avatar
      Big Al from Oz

      Do you know what efficiency is?

      FE is what the game is.

      • 0 avatar

        yes, it’s how much power you get out of an engine per unit of fuel burned. you know, efficiency as defined by thermodynamics.

        a spark ignited piston engine only reaches its stated peak efficiency number when it is running at wide-open-throttle at the RPM it produces peak torque.

        • 0 avatar

          Most definitions of efficiency in thermodynamic contexts use net work as the numerator rather than power. The distinction is subtle but important.

          Torque peak and WOT are usually a good guide but it doesn’t always work like that. Something like 75% engine load and ~2k-3k rpm seems to be the sweet spot for most car engines.

          Check it –

        • 0 avatar

          Peak efficiency is part of the equation. Much of the gains in fuel efficiency today have come from maximizing peak efficiency AND keeping the engine operating at that point with 10 speed transmissions.

          If this can lift overall efficiency (which given its elimination of a valvetrain and like 90% of the friction surfaces should be a given), then it should be no biggie at all. If they wanted to get really fancy they could replace the transmission with a huge full wave AC-DC rectifier to really keep the engine running at its sweet spot at all road speeds.

    • 0 avatar

      Auto manufacturers are like oil tankers. For example Pattakon and Koenigsegg have already developed running prototypes for the next era of valvetrains. But between conservatism and patent fears manufacturers have to lay low. Just because a manufacturer hasn’t adopted a technology doesn’t make it BS, and as we’ve seen many times, just because a manufacturer comes out with a tech doesn’t mean it’s fully cooked.

  • avatar

    I thought gas engines ran best at about 70% rpm to get the best combination of torque and horsepower. Diesel run better at 90% rpm as I recall from my truck selling days.
    anyway, with a prius getting 50mpg i don’t think that a new style engine will work out that well. better for toyota and others to keep working on their existing products.

  • avatar

    Miraculous ICE engines which for various reasons never make it into volume production are as old as the automobile. I was born in 1961 and these miracle engines keep being introduced with a bunch of fanfare only to whither away. Some got pretty far down the development and production pipeline (Chrysler Turbine and Rotary), but so far, nuttin.

  • avatar

    I am still waiting for the Villella Gyro-rocyprocating motor. That and my personal jetpack.

  • avatar

    Guys, lets stop with the “herp derp its a 2 stroke”. Yes, it has no valvetrain, but it also has no crankshaft or rods either. A 2 stroke doesn’t use the piston to generate electricity either.

    One thing I’m wondering… could they use electromagnetism to keep the piston from touching the block? That would immediately solve the two stroke oil emissions problem.

  • avatar
    Brett Woods

    “The engine Fridman describes sounds an awful lot like a version of the free piston engine “linear generator” under development by Toyota. Word first leaked out about that automaker’s efforts two years ago.”

    I wonder if Toyota is developing the linear generator or just sitting on it. All I saw reported were some “patent-applied-for” diagrams. Toyota could use a coil over magnet in parallel with the suspension of a plug-in to re-capture energy if they decided to get creative.

  • avatar

    The last three lines are crucial… People do mind the long charging time and the still relatively high costs of EVs. If the first isn’t solved, then this new power plant does make a lot of sense. What the Israelis face, is the “heck, we haven’t invented it” attitude of car makers, that spent billions on developing engines. And there is the issue of emissions, that is being ignored by the makers. Not a good sign.

    Btw, this picture suggests it does look like the Toyota contraption. Questions? No patent infringement? And why isn’t Toyota pursuing further development?

  • avatar

    Does it come with a 200 mpg carburetor?

  • avatar
    SCE to AUX

    Just imagine the result if Fisker paired this with his graphene supercap battery.

  • avatar

    Sounds like a serial hybrid in which the free-piston engine is operating a shake-weight generator (as seen in flashlights). I would think this would have been tried by the late 1800s… I suspect it’s not a very efficient combination.

    Sure, modern materials would improve efficiency, but waste heat from the engine is going to increase the resistance in the generator windings. So you can add a radiator, and a coolant pump, etc. and soon you’ve recreated the rube goldberg machine that is the modern ICE. One of the main benefits of battery electrics is getting rid of all that.

  • avatar

    We’ve already seen the return of wagon wheels, and Mercedes is bringing back the inline six, and the ethanol lobby is trying to bring back Henry Ford’s favorite fuel. We might be looking at the Model T’s requirement of an engine overhaul after 10k miles next.

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