By on November 25, 2011

Toyota’s Chief Engineer Satoshi Ogiso figures that efficiency improvements of traditional gasoline engines may soon hit a wall. He gives the gasoline engine an improvement potential of “maybe 10 to 20 percent.” Today, we have proof that it is a fight of diminishing returns. Mazda is now at a point where it saves up to 10 percent of gas by idling the alternator. How is that done?

Mazda’s developed a regenerative braking system that uses a capacitor. Compared to batteries, a capacitor can be charged and discharged rapidly. Also, it does not wear out like a battery. Mazda stores the regenerated energy in the capacitor. It does not use it to power the car. That would need a hybrid system Mazda does not have. Also, even the new Electric Double Layer Capacitor (EDLC) Mazda uses would not get you far. Instead, Mazda uses the electricity to power the climate control, the audio system and other gizmos in the car that want electric power. As we know, the gizmos proliferate with abandon. And why does that save gas?

The electric power generated by the car’s alternator does not come free. The alternator demands power from the engine. As a rule of thumb, 5 hp are usually used, however, this changes with the amperage and type of the alternator.

Mazda calls its system “i-ELOOP.” It comes from “Intelligent Energy Loop.

The system uses a new 12-25V variable voltage alternator, a low-resistance electric double layer capacitor and a DC/DC converter. ‘i-ELOOP’ starts to recover kinetic energy the moment the driver lifts off the accelerator pedal and the vehicle begins to decelerate. The variable voltage alternator generates electricity at up to 25V for maximum efficiency before sending it to the Electric Double Layer Capacitor (EDLC) for storage. The capacitor can be fully charged in seconds. The DC/DC converter steps down the electricity from 25V to 12V before it is distributed directly to the vehicle’s electrical components. The system also charges the vehicle battery as necessary. Says Mazda:

“As a result, in ‘stop-and-go’ driving conditions, fuel economy improves by approximately 10 percent.”

The system will begin to appear in Mazda vehicles in 2012.

Mazda does not have hybrid technology and instead is betting on optimizing the ICE with Mazda’s Skyactiv Technology and other fuel saving tricks. As we see, the engineers have to get very creative to save a few more drops.


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40 Comments on “Mazda Uses Capacitor To Save Gas...”

  • avatar

    This is a practical (and affordable) demonstration of the value of so-called “supercapacitors” in motor vehicle applications. Soon, super cap energy density and rapid charge/discharge ability will be combined with advanced batteries to produce EV’s with longer range and higher initial torque, as well as being better able to take advantage of brake regen energy by rapidly absorbing it, then applying it to the batteries in a more “gentle” fashion.

    • 0 avatar
      Volt 230

      you want to save gas, put in a button in the A/C controls to make the compressor work less on those days that are not really that hot,(my 86 Camry had it) or put auto temp control on all cars and skip the stupid nav systems, this alternator idea will likely increase the cost of replacing the damn thing when it goes, and there go your savings.

    • 0 avatar

      Supercapacitors or Ultra capacitors are already in common use in UPS designs. Extending the use of superconductors to automotive applications makes common sense particularly if you have a short term high inrush current demand such as when a starter motor is operating. A supercapacitor can discharge as quickly as it is charged with no effect to its lifespan. This makes a supercapacitor a much more suitable energy storage device for such transient loads than a battery.
      The big challenge for supercapacitor design is the need to make sure the voltages at maximum charge and discharge stay within a narrow range (1.8 V DC max and .4 V DC min in the case of the ones I used) or the supercapacitors will fail. This means you must design a good balancing circuit to keep all the capacitors in series evenly charged and have a high current capacity bilateral buck/boost DC-DC converter in order to get a useable voltage out of the capacitors and have the ability to charge the supercapacitors.

      • 0 avatar

        Yes, VLS_GUY, external circuitry requirements are high to utilize a useful percentage of the stored energy, and the voltage-balancing is tricky (and leaky), too. But with power densities going ever upward (nanotubes will give a big jump), and the development of hybridized versions (combined with lithium chemistry – so called “ultrabatteries”), this could be the perfect combo for the “300-mile” electric” that most everybody could live with.

        (Oh, and thanks to Wikipedia for the primer ;-) )

  • avatar

    I recall that the new Audi A4 and A5 have a clutched alternator and braking energy recovery as well. Maybe not with a clever acronym, though. And I don’t know which other VW Group cars have that.

  • avatar

    I think there would be a future for electric cars if they used these kind of capacitors.

    I wouldn’t mind to have only 150 miles of range if it was possible to recharge almost instantly.

    • 0 avatar

      Capacitors simply don’t have the ability to provide high currents for long periods of time. They’re good for brief spikes, or longer drains at very low levels. The cap they’re discussing here does its thing for only a few seconds, and is enormous considering how much energy it holds.

      • 0 avatar

        A capacitor of that size would be scary beast, more dangerous that a battery of the same capacity. Not only can you charge capacitors fast they can also discharge fast too.

        This is a bit like KERS (Kinetic Energy recovery system) used on Formula 1 cars, they have special safety procedures to work on those cars in the garage. This is KERs lite with lower voltages etc.

      • 0 avatar

        @ExPatBrit: My thoughts exactly. Using the alt, engine inertia & the cap to make a ‘Thin-Client KERS’ with only 1 extra part & a few wires.

        They Really Do have some clever bastards over there @ Mazda!!!

        ==>Now SKYACTIV + this makes it 44MPG in the 3, then?

      • 0 avatar

        The improvement in mpg will be for stop-and-go traffic, not hwy. Also, this technology appears to be intended for use with their i-Stop to power the car’s electronics when the engine is off, thus removing the load & wear-and-tear from the battery.

        I can say from personal experience that an engine shut-off feature like the i-Stop does save around 10% in real-world city driving. Combining the two techs may give the Mazda3 mpg numbers of ~31/40 up from 28/40. (The EPA tests don’t include much idle time so engine stop tech doesn’t affect ratings much on its own.) Those numbers may go up more when they release the next gen Mazda3 in a couple years. That engine will have a higher compression ratio, and the car should weigh a couple hundred pounds less. That car may have numbers ~32/42.

    • 0 avatar

      Aside from the issues with capacitors already noted, it’s worth understanding that you can’t charge your car in an instant because it would take a massive electrical service to deliver the power.

      A fuel pump pushes over a huge amount of energy into your car at a rate of well over 1 megawatt. An electrical line cannot do that. Electric car charge times are limited by the plug into the wall, not the batteries themselves. A 15A wall circuit will recharge a usual electric car in around 12 hours; a 70A dedicated circuit will chop that time way down.

      In fact, there is a lot of discussion about putting a battery on the other side of the charger. The battery would store up power slowly at night using off-hours power, then deliver it en masse to a vehicle when needed, providing faster charge times than what could be achieved pulling power from the grid. Obviously, that’s expensive right now, and there is an efficiency loss from storing the power twice.

      People get on the case of electric cars, but I think they really just don’t understand how much chemical energy is in gasoline. It shouldn’t be huge surprise that it takes some R&D to get electrical storage and delivery to the level of concentrated chemical fuel.

  • avatar

    I get a feeling that the auto industry is nearing a major breakthrough on efficiency, but it appears to be centered on smaller cars. A guy like me who drives a long commute at my age wants a comfortable car, a larger car, Malibu-sized and larger, Impala-sized. Until someone can wrangle 45-50 mpg out of a larger car, any developing tech will be restricted to smaller vehicles, hence, a smaller piece of the market. Man, I sure hope I’m wrong, because I read these articles with great interest.

    Even though I owned an Impala SS many years ago, I have never been particularly interested in brute horsepower over the long term, because it costs money, and I hate to waste my dollars on gas! I am and have always been just a cruiser, and though I enjoy my MX5, it still gets up to 32 mpg, which makes me smile!

    What I wouldn’t give to have a new Impala that nets me 45-50 mpg! After all, I can dream, can’t I?

    • 0 avatar

      Even though more efficiency in cars is a good thing, the vast majority of Americans do not care about the price of gas or energy. If they did, Americans would not be so wasteful with energy, and I count myself among those who are wasteful with all forms of energy I use.

      Americans complain about the price of gasoline and yet at the same time we have fossil fuels to spare and sustain us for hundreds of years.

      Improvements like these are nice of course, but this whole energy thing is driven by the uber-leftist environmentalist green-weenies. Until we start to develop and utilize our own natural fossil resources, these improvements are just going to add unnecessary expense to our vehicles.

      Let’s develop our natural resources instead. We have so much that we would become an energy-exporting nation if we only developed our own resources.

      • 0 avatar

        I think our current policy makes sense – use everyone else’s resources while they’re still cheap, then if they start to run out and become expensive, tap into our own.

      • 0 avatar

        Actually a lot of conservatives buy into the need to reduce fossil fuel consumption. Sam Brownback, the conservative former senator from Kansas told me that he owns a Prius and a Civic hybrid because he feels he needs to take personal responsibility towards reducing energy consumption. At the time I spoke with him he had recently read a book entitled “Serve God: Save the Planet.”

      • 0 avatar

        highdesertcat – To suggest that “the vast majority of Americans do not care about the price of gas or energy” means you are OUT OF TOUCH with the vast majority of Americans.
        You say that we don’t care about the price, then you say we complain about the price. Then you say ” this whole energy thing is driven by the uber-leftist environmentalist green-weenies” What exactly do you mean when you say this “whole energy thing”?
        Having untapped natural resources doesn’t equal consumers not caring about the price of fuel. Not sure how you arrive at that statement or conclusion. ? I’m not trying to bash you or start a big left -right thing here, I just don’t follow the logic.

    • 0 avatar

      It starts to look like diesel is the solution. The Passat diesel looks like it might be a larger car with good economy. I would still like to see a diesel-powered LaCrosse, or Charger, or Fusion…

    • 0 avatar

      I hope you get your 45-50 mpg Impala. In fact, I hope it’s a ’64 SS. I suspect I’ll get a skyactive mazda at some point in the future. I prefer my ICE straight, like my bourbon.

      I suspect there’s more potential for boosting the fuel efficiency of ICE, and if hybrids hadn’t absconded with all the green cachet in the US, we’d probably be seeing more interesting developments in ICE. Here’s an example:

      • 0 avatar

        Interesting, David. Unfortunately, only really applicable at or near full throttle, no matter the revs.

        99% of the time, we cruise around on an almost closed throttle, meaning there is almost a complete vacuum in the intake manifold of a gasoline engine. The actual amount of air that gets into a cylinder is tiny. Compressing it on the compression stroke may give you an effective CR of 2 or 3 compared to atmospheric if you’re lucky, even if the geometric CR is 10 or more to 1. No wonder the gasoline engine is so inefficient at low load.

        The diesel always inhales a full cylinder’s worth of air, more if a turbo is at work. So effective CR is commonly well over 20. Power is regulated by how much fuel is injected, and excess air is always present. That gives high thermal efficiency all the time.

        The gasoline engine is inherently a variable compression ratio device at anything less than full throttle. That’s the way it is, which is why I laugh at attempts to make a variable CR engine. What help would it be at 2000rpm and one quarter throttle? You’d need a geometric CR of 30 or more, and that gives no room for valves and spark plug even in the closed position, sitting just proud of their seats.

        I don’t much like diesels, but they are inherently more efficient at less than full power at a given rate of rotation. Just the way it is.

        So why are all these bright ideas for gas engines always touted as the next breakthrough? Does everyone forget the reality of lightly-loaded engines? Variable displacement is the only thing that’ll help the gas engine. Perhaps on a V6, only one cylinder working at max effort to provide the required power for cruise is really needed. Then you can apply all these bright ideas to that one cylinder, and make it more efficient. Good luck with balance and vibration!

      • 0 avatar

        Ethanol boost? Or… in other words… alcohol injection?

        Nothing new… in fact, you can get a good percentage of the same effects with straight water used for knock control.

        It’s a cheaper method of limiting knock and heat build-up in ultra-lean burn strategies with a gasoline engine (alcohol/water injection also works on diesels), but as GM found, getting people to remember to fill up BOTH tanks on a factory car is a bit difficult.

        I would like to see someone go with a factory installed water injection system as an alternative to gasoline-direct injection or as a supplement to it.

      • 0 avatar

        There may be other ways to get the water. The AC compressor has a dehumidifier, and the water it extracts is essentially distilled water. I have no idea how much water it produces, but I do know a house AC unit can produce 50 gal/day or more depending on tonnage, temperature, & humidity. (Frankly, I have no idea why house ACs dump the water straight down the drain instead of into a storage tank to water the lawn.)

  • avatar
    Paul W

    Yeah, yeah, whatever, I want to know if it comes with a FLUX capacitor!

  • avatar

    What happens when the system has a flaw and sends 25V to 12V accessories?

  • avatar

    A smart alternator that only produces electricity when you are braking has been done before, it is combined with a starting battery with some deep cycle abilities since the alternator will not be working while on cruise.

    The future is a mild hybrid such as GM’s eAssist, as long as they can keep costs down. A motor/generator that replaces the starter, alternator and can also provide a bit of torque on demand. Please keep the cost down or the benefits will never materialize. A cheaper version would still replace the starter and alternator, but not proved any torque to the wheels.

  • avatar

    Caps make sense for city driving, and a whole lot more sense than batteries, if only for the energy density. The unfortunate thing is that they would have to be insulated/shielded for collisions -> size/weight.

  • avatar

    Whatever happened to the ultracapacitor race car ideas from a decade or so ago?

  • avatar

    Can flywheels be far behind?

    • 0 avatar

      Flywheels? ‘Way behind – 40 years ago!

      • 0 avatar

        Well, electric cars came back, and hybrids (diesel electric) have been powering railroad locomotives for 75 years. The only downside to the flywheel is that a heavy rotating mass might just have little negative effect on cornering.

      • 0 avatar

        Another negative effect of a flywheel is that it adds to the overall weight of the car more than a capacitor would and probably more than a battery pack would. Also, if the NHTSA is concerned about the dangers of a battery in an accident, just think what could happen if a full-spinning flywheel gets damaged in an accident.

  • avatar

    As a rule of thumb, 5 hp are usually used, however, this changes with the amperage and type of the alternator.

    5 hp? That seems more than a little high. Even assuming this alternator is unusually inefficient for a generator at 75%, that’s about 200 amps of output!

  • avatar
    Greg Locock

    Alternators are only about 40% efficient at typical operating conditions. Even so I agree, 5 hp is a lot. Switch all the electrics off in your car at idle, note the fuel consumption on that handy little readout you never look at. Now switch everything on (not the AC). It’ll bump up by maybe 0.04 gallons per hour. That ain’t 5 hp.

  • avatar

    Most of these “breakthroughs” seem to be expensive solutions to miniscule problems.

    The cost of all these systems just so you can put a less powerful alternator and save 1-2 horsepower from electricity production?

    To the average motorist, your talking pennies a week in saved fuel costs, only to be offset by thousands more tacked on to the cost of a new vehicle for such an elaborate system, and let’s not even get started on what these dealer-only type repairs and parts are going to be in the future when they eventually wear out.

    • 0 avatar

      A car consumes about 15-20hp while cruising on the hwy, if you can save a miniscule 1-2hp using a gizmo like this then you would have a 10% fuel savings.. thats very respectable.

      For the Impala guy.. if most of your driving is hwy then get the new diesel Passat, if you do some city driving then the best one would be new Camry hybrid.. both very confortable midsized cars but you will pay a premium over a fleetqueen Impala.

      • 0 avatar

        Your math is way off in a real world application, you’re not going to get that kind of consistent mileage increase by just putting on a different alternator that puts out less amps.

        Installing a heavier duty alternator that produces more amps is a common upgrade on many vehicles, and it barely makes a blip on observed fuel economy. It certainly doesn’t kill fuel economy by 10%.

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