Brake regen is typically associated with electrified cars, converting kinetic energy recovered under braking back into juice for the battery pack. Mazda, however, has been using a system it calls i-ELOOP on a few of its gasoline-powered cars like the 6 to recoup that energy to store in a capacitor and serve in place of the engine-powered alternator for an impressive increase in fuel economy and power. A few months ago this system was added to Japanese-market MX-5s, and this week it was added to European-bound exports.
Traditionally, cars have used an alternator to charge a battery, which is in turn used to power your car’s electrical components from headlights and windshield wipers to the HVAC system and infotainment. It’s worked like this more or less since the 1960s.
Because the alternator on the front of your car’s engine takes at least some percentage of your engine’s power to operate at all times, it makes your acceleration times slightly slower and your fuel efficiency slightly worse. Mazda aims to take this out of the equation all together by only running the alternator during times when your foot is off of the accelerator.
The time it takes to brake your car down to a stop is generally pretty quick, so Mazda was forced to employ a variable voltage alternator capable of zapping up to 25 volts as necessary into a high efficiency capacitor. The capacitor is then used to do all of the things an alternator would normally do during your acceleration and steady state throttle runs, from charging up the battery so you can start your Mazda up again in the morning, to powering your stereo.
The added strain it takes to turn this high-power alternator probably does add some more force to your engine braking, so I guess it could be called regenerative braking, but it’s a bit of a misnomer from where I’m sitting. It’s more of a fancy alternator.
At any rate, without the alternator churning away sapping power at highway speeds, the MX-5's rated 35 mpg highway should turn into something just shy of 37 when this i-ELOOP system is employed. And, because this system includes nothing more than a beefed up alternator, a capacitor, a dc-dc converter, and some heavier gauge wiring, it shouldn’t add too much weight to the featherweight MX-5 sports car. A similar system employed on the Mazda 6 since 2014 weighs just 20.5 pounds.
There isn’t any word from Mazda on whether this system will be added to U.S. spec MX-5s. Being that we love our long stretches of open road, Mazda probably wants those big numbers for highway MPG, so I wouldn’t bet against it. Really, if it does everything Mazda says it does, there’s no reason a system like this shouldn’t be in every car.