Audi takes aggressive stance with diesel in the US; four new models and new 3.0L diesel engine; challenge to policymakers
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Mazda to offer diesel Mazda6 in North America in second half of 2013; i-ELOOP and SCBS

System components of i-ELOOP, which makes its first production appearance on the Mazda6. Click to enlarge.

The 2014 Mazda6 sedan made its North American debut at the Los Angeles Auto Show. The first version, equipped with a SKYACTIV-G 2.5-liter gasoline engine, goes on sale in January. The SKYACTIV-D-equipped diesel version will follow in the second half of the year, making Mazda the first Asian manufacturer to offer a modern-technology clean-diesel engine in a non-commercial vehicle in North America.

The 2014 Mazda6 also will be the first production vehicle to feature Mazda’s capacitor-based brake energy regeneration system called i-ELOOP, featuring a new 25V variable voltage alternator.

According to Mazda’s roadmap, the most effective next step in increasing engine efficiency was to optimize the compression ratio. For the SKYACTIV-G engine, this meant increasing the compression ratio to 14:1 (13:1 for North America). For the SKYACTIV-D, this mean reducing the compression ratio to 14:1. (Earlier post.)

The new Mazda6 will be available with a choice of SKYACTIV transmissions in either the SKYACTIV-Drive six-speed automatic or SKYACTIV-MT six-speed manual.

The SKYACTIV-G 2.5L is estimated to produce 184 hp (137 kW) at 5,700 rpm and 185 lb-ft (251 N·m ) of torque at 3,250 rpm. Performance estimates for the SKYACTIV-D clean diesel engine are not yet available.

Expected to offer a high amount of torque as well as cleaner combustion, the SKYACTIV-D 2.2L is 10% lighter than the current MZR 2.2-liter diesel engine sold in other global markets. Other improvements include internal engine friction reduced by 20% and fuel economy increases by up to 20%.

This is achieved by using a new two-stage turbocharger, which delivers a smooth and steady response across the engine range (up to 5,200 rpm). Also, with the ultra-low compression ratio, the SKYACTIV-D diesel engine burns cleaner and discharges fewer nitrogen oxides to produce virtually no soot, thus requiring no additional NOx aftertreatment as is typical of conventional diesel engines.

Final specifications for all 2014 Mazda6 models will be available closer to the on-sale date. Standard features, optional packages, and pricing also will be released at a later date.

SCBS. An all-new safety component called Smart City Brake Support (SCBS) will be offered and is designed to assist a driver in avoiding front collisions when traveling at speeds of less than 30 km/h (18.6 mph). An embedded laser sensor detects an obtrusive object and will reduce the brake rotor travel to quicken braking should the system calculate that there is a risk of a collision occurring. If the driver fails to perform an avoidance maneuver, the SCBS system will activate an automatic braking function.

i-ELOOP. Derived from “Intelligent Energy Loop,” i-ELOOP, Mazda’s in-house developed brake energy regeneration system, is all new and makes its first production vehicle appearance in the 2014 Mazda6 after first being introduced globally on the TAKERI Concept.

Generally, notes Mazda, about 10% of fuel energy is used to power the 12-V alternator which generates the electricity that a car needs to function. Current cars are being fitted with safety and environmental technologies in increasing number and require significantly more electricity than in the past.

As part of a growing number of fuel-saving technologies, brake energy regeneration systems use an electric motor or alternator to generate electricity as the vehicle decelerates, thereby recovering a portion of the vehicle’s kinetic energy to power electrical components, such as air conditioning and audio features.

i-ELOOP is the first capacitor-based brake energy regeneration system to provide power to all the electrical mechanisms in a vehicle, Mazda says. Other capacitor-based systems have been used to provide electricity to a single vehicle component or motor.

Compared to systems utilized in hybrid vehicles, i-ELOOP avoids the need for a dedicated electrical motor and battery, making the system more efficient, compact, and lighter than traditional systems. Also, capacitors have the ability to charge and discharge rapidly as well and are resistant to deterioration despite prolonged use. In real-world driving conditions which can require frequent acceleration and braking, i-ELOOP is expected to improve overall fuel economy but is dependent on road conditions and driving habits.

i-ELOOP performs three functions; ‘regeneration’, ‘storage’ and ‘use’. A big focus of the development was how to generate and store electricity as efficiently as possible because the opportunity to do this, the period when a car is braking or decelerating, is by nature very short.

i-ELOOP features two main technologies:

  • A variable voltage alternator, capable of producing up to 25 V and 200 amperes, which is used to convert the car’s kinetic energy into electricity.

  • A low-resistance, high-capacity electric double layer capacitor which is used to store the electricity after regeneration

The variable voltage alternator can freely control its output voltage between 12 V and 25 V and continually supplies electricity until the capacitor reaches its maximum capacity of 25 V. The alternator efficiently feeds electricity into the capacitor because its voltage increases smoothly up to the maximum 25 V and always stays higher than that of the capacitor. Capacitors are the ideal storage device for use in brake energy regeneration systems due to their ability to be charged and to release their charge quickly. This is because they store energy as electricity and do not require a chemical reaction. For the same reason they exhibit very little deterioration of the electrodes.

Electricity generated by the alternator is stored in the capacitor at up to 25V so a DC-DC convertor is used to drop the voltage to 12V standard for vehicles and their electronic components. If the electricity available exceeds what the car is actually using, the excess electricity is used to charge the lead-acid battery.

Through the combined use of the capacitor and the variable voltage alternator, i-ELOOP is capable of regenerating about 3 times the energy of existing regeneration systems which use only alternators and lead-acid batteries, Mazda says. It has also made it possible to supply almost all the electricity the vehicle needs when driving through the regeneration system, freeing the engine from the work.



These are two great new powertrains. Really want to see them in the Mazda 5!

Nick Lyons

Smart: lightweight, efficient, low cost. Next add idle/stop.


This is really a smart car, pitty that Mazda didn't do more effort to design a more aero car, it wouldn't take so much to get the Cd to 0.2 and offer free gaz saving of 15% on the highway.

Roger Pham

It seems counter-intuitive that the variable-voltage alternator is used just to charge the ultra-capacitor, and not used to provide power to assist the vehicle in acceleration, like a motor-generator would do.

This is because in frequent stop-and-go situation, a lot of braking energy will be recuperable, yet, the storage capacity of the ultra-capacitor is still very limited, and the vehicle electrical system cannot possible consume all the electrical energy recuperable during this brief amount of time! Furthermore, the alternator of a few kW of power is far too weak for sufficient braking energy recuperation. The Prius II has a battery of 21 kW of power and one must brake gently to recuperate enough of braking energy, or else, the energy will be wasted in the brake pads. So, a scheme at least like the Honda IMA, with at least 21 kW motor-generator will be required to allow for sufficient braking energy recuperation in gentle HEV drivers. For a typical driver, only a PHEV with high power battery and motor-regenerators can allow near-complete braking energy recuperation!

Charging the lead-acid battery using this excess electricity? Automotive lead-acid battery is not designed for deep-discharging, and is supposed to be fully-charged all the time in order to maintain its life span, which is sadly, still too short, and will deteriorate in a few years.

It seems that LiFePO4 battery is now cheap enough to replace lead-acid battery, and LiFePO4 battery is far smaller and lighter than lead-acid battery, and would last longer, too!


I presume the braking energy goes quickly into the capacitor and then slowly into the lead acid battery.
This takes much of the load off the alternator (and engine during normal driving).
The purpose is to avoid wasting braking energy, it can be used later on in the car electrics, it does not need to be used as acceleration assist (although it would be good if it could be).


It is nice to see that they meet US emission limits without any kind of NOx aftertreatment on the diesel version. This must be a very cost-effective solution compared to aftertreatment. Some of you might remember that I have projected in the past that this would happen. When certification data for the Euro 6 version was made available some time ago, it was apparent that the NOx level was quite close to the limit. Nevertheless, it is obvious that US and EU NOx limits are roughly equally tough also for diesel cars as for gasoline cars, regardless of that the actual numbers in the regulations differ.

One feature that has surprised me is that they do not use any low-pressure EGR, as several other manufacturers do. Low-pressure, or long-route EGR, is advantageous if you want to reduce NOx emissions, it can work at higher load (than high-pressure or short-route EGR) and improves transient response of the engine. DPF must be used with low-pressure EGR but this is a necessity anyway. In the latest issue of the German MTZ Journal, an article about the new VW group 4-cylinder engines was published. All these engines (from 1.6 to 2 liters) use low-pressure EGR and with very nice packaging together with indirect charge air cooling as well. VW has used both low-pressure and high-pressure EGR on the US diesels but having seen the new solution, it seems obvious to me that only low-pressure EGR will be used in the future.


The capacitor system is another welcome variation of the mild hybrid.

This may bring the capacitor, which offers high power but low energy into the mainstream.

Cost is all-important.

I believe the buyer will look at the options;

• Normal ICE
• Diesel
• Mild Hybrid
• Full hybrid

And decide if the moderate increase in MPG and lack of green image is worth the cost and risk.

The GM two-mode hybrid transmission is costly, has unknown maintenance risk, provides considerable increase in MPG (but MPG still sucks on a big vehicle) with no glory.

Belt alternator starter (BAS) cost was more moderate but not very exciting.

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