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Mazda's i-ELOOP regenerative braking system. (Mazda/Mazda)
Mazda's i-ELOOP regenerative braking system. (Mazda/Mazda)

How it works

Mazda: the little car maker that can Add to ...

For many years, tiny Mazda was part of the Ford-Volvo-Aston Martin, etc., conglomerate, but its engineering contributions were inordinately out of whack relative to its small size.

The small Japanese company developed and produced not only entire small vehicle platforms, but most of the four-cylinder engines used by the other partners.

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Once Ford sold its controlling interest, Mazda was once again where it has been since its foundation in 1920 – a small independent car company, one based on engineering and innovation.

It was the first and only company to make the rotary engine work in volume production vehicles – the RX-series of sports cars were the most widely known. It was, and is, the only company to make the Miller cycle engine work in volume production vehicles – first the tiny supercharged V-6 in the Millenia luxury car sold here and since then a four-cylinder version in the Demio subcompact for the Asian market.

Mazda plans to concentrate on the internal combustion engine because it lacks the size and bottomless pockets necessary to play with hybrids and pure electric vehicles merely for the sake of being in that game. The IC engine will continue to be the mainstay of the industry for decades to come, whether in standalone applications or in concert with electric motors in hybrids. Knowing this, Mazda has set a corporate goal of continual refinement of the IC engine.

Its first fruits of this are two new engines under the SkyActiv banner that defy conventional logic: a four-cylinder gasoline engine with the highest compression ratio of any production engine and a diesel units with the lowest compression ratio. Also part of the SkyActiv system are similarly innovative new automatic and manual transmissions. Combined, the result is a 20 to 25 per cent improvement in fuel economy.

Those are just the introductory efforts in what is an amazing display of innovation.

Next will be a regenerative braking system that uses a capacitor and alternator and a stop-start system that uses compression rather than bulky and heavy batteries and electric motors.

Mazda is calling the regenerative braking system i-ELOOP. It says the name is an adaptation of “Intelligent Energy Loop” and represents Mazda’s intention to “efficiently cycle energy in an intelligent way.”

The groundbreaking system will begin appearing in Mazda vehicles in 2012, bringing fuel savings of up to 10 per cent under real world conditions that involve frequent acceleration and braking – i.e., urban driving and heavy traffic.

Regenerative braking systems are common in hybrid, plug-in hybrid and pure electric vehicles; they capture the kinetic energy generated during braking and commonly use a large electric motor, alternator or generator to generate electricity and a heavy and bulky storage battery.

Mazda engineers studied these systems and came up with a new one, a highly efficient method of recovering a large amount of electricity each time the vehicle decelerates – without the need for a dedicated electric motor and battery. Its solution is a giant capacitor. A capacitor is a passive two-terminal device, formerly known as a condenser, used to temporarily store large volumes of electrical energy.

Unlike batteries, capacitors can be charged and discharged rapidly and are resistant to deterioration through prolonged use. The electricity generated during deceleration is used to power the climate control and audio system as well as other electrical components.

The instant the driver lifts off the throttle, the system goes to work. The alternator generates up to 25 volts before sending it to the capacitor for storage. The capacitor, developed specifically for this application, is fully charged in seconds. The converter steps the voltage down from 25 to 12 volts before it is distributed directly to the various system components. It does double duty – charging the vehicle’s main battery as necessary.

The new regenerative braking system will be used in conjunction with another Mazda innovation, “i-stop”. This idle stop technology has been in use in other markets around the world but not here yet because federal fuel mileage calculations do not take it into account, negating the added expense of incorporating it in a vehicle.

But with the growing use of idle-stop systems by a number of manufacturers – and the resulting significant reduction in fuel use and exhaust emissions – new test procedures will recognize their contributions.

Idle stop system are employed to eliminate the waste and emissions created as a car idles while stopped. They shut the engine down when the vehicle comes to rest for more than a second and restart it when the driver removes his or her foot from the brake pedal. Conventional idle-stop systems employ a big battery and electric motor or heavy-duty starter to spin the engine back to life in the same process used to start normally.

Mazda’s “i-stop” system does away with the need for heavier batteries and starters. It uses compression. Using electronics and direct injection, the Mazda system stops the engine with the compression stroke and expansion stroke pistons stopped at a precise point to create the correct balance of air volumes. When it comes time to restart, the system identifies the initial cylinder to fire, injects fuel and ignites it, generating a downward force. Subsequent cylinders are continuously selected for ignition and the engine is up to idle speed almost instantly.

The Mazda system not only eliminates the need for heavier and bulkier components, it restarts the engine more quickly and quietly than conventional systems. The engine returns to idle speed within 0.35 seconds, about half the time required by other systems.

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