How Electric Superchargers Went from Fantasy to Feasibility

popularmechanics.com ^ | October 30, 2014 at 11:30:00 AM | David Gluckman

[ckilmer]

How Electric Superchargers Went from Fantasy to Feasibility

October 30, 2014 at 11:30:00 AM by David Gluckman | 0 Comments

 

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(Photo Credit: Chris Philpot)

Until recently, electric superchargers might as well have been perpetual motion machines, for sale at the same places as gasoline magnet ionizers and other snake-oil. Power for an electric compressor has to come from somewhere, and e-turbos were a kind of get-power-quick scheme that ultimately left you poorer.

That’s starting to change. Step one, as it usually does, involved motorsports. The current crop of Formula 1 cars and Audi’s latest R18 use turbos that are a mash-up of an exhaust-driven compressor and an electric motor, allowing them to both harvest and unleash electricity. They’re highly complex and expensive ways of storing energy that make more sense for competition than commuting, however.

READ MORE: How Formula 1's amazing hybrid electric turbochargers work

Before we dive into why electric superchargers finally make sense in the mass market, a little refresher on how they work is warranted. An electric supercharger looks and acts a lot like a turbocharger, and its job is to compress air that is then used to spin up a conventional turbo.

Most of the non-racing applications of the technology are in some respects similar to the older idea of twin-charging: using a supercharger and a turbocharger in conjunction. Volvo’s production T6 Drive-E engine, which pairs a conventional engine-driven supercharger with a turbo, is a twin-charged engine. The High Performance Drive-E concept is even more exotic, using one electric supercharger to feed twin exhaust-driven turbos. The e-supercharger takes care of low-speed boost and transitions, while the exhaust-driven turbo or turbos handle the high-rpm tasks they’re good at.



Which brings us back to the problem of power supply. Siphoning juice from the 12-volt system won’t cut it for several reasons—there’s the net-loss issue and the fact that batteries are no good at accepting or supplying lots of power quickly. The answer is a supercapacitor. This is the technology that takes electric supercharging out of the realm of snake-oil fantasy and into legitimacy.

Power recovery can be supplied by a clutched alternator, similar in function to the regenerative braking found in hybrids and EVs, that kicks in only when the car is slowing. To release the recovered energy, electricity is sent from the capacitor through a DC/DC converter for voltage correction and onto the electric compressor. The result is lag-free power delivery from a smaller engine. And instead of trying to power the electric compressor directly from the engine, it instead uses recovered energy. Everybody wins.



READ MORE: The low-down on twin-charged engines

Supercapacitors are also longer-lived than batteries in terms of repeated charge and discharge. And while they have low energy density—you can’t pack a lot into one compared to a battery of the same size—it’s not a worry in this application since the energy is being used in short spurts. It’s not moving the entire vehicle, like an EV’s batteries—instead, it’s just spinning up the turbine for a brief period.

You can already buy a car equipped with a supercapacitor, and it’s not some million-dollar hybrid supercar. Mazda’s efficiency-focused i-Eloop system feeds a supercapacitor and then uses the power to run the car’s various electric components—but not an electric compressor. The aim is improved fuel economy alone, not extra boost, although eliminating the alternator’s drag does result in more usable horsepower. The system could, theoretically, power an electric supercharger instead of the Mazda's accessories, if Mazda wanted to go that route.

Sound hybrid-pricey? Supercapacitors are generally more expensive to make than batteries, but costs are coming down. Mazda’s system comes as part of a big $2600 tech package on a $27,000 Mazda 3, so it’s safe to say the supercap is ready for the mainstream.



The other hurdle concerned programming the controls. Michael Fleiss, Volvo’s VP of Powertrain, says making everything in the complex Drive-E concept’s three-turbo system work together was the tough part for his team. There’s a lot going on in the 450-hp 2.0-liter engine, more so than a “conventional” twin-charged engine. In addition to the complex plumbing, there’s wiring to feed and support the supercapacitor. Plus the different turbos need to be cued with wastegates for the exhaust-driven units and a bypass throttle that sits parallel to the e-booster. And it all has to happen smoothly, with no lag, surge, or hiccups.

Thank the electrical super-geniuses for what will be a more pleasant engine downsizing experience. It’s not the zero net loss of perpetual motion, but things are getting closer.

READ MORE: How electric superchargers work

Originally published at Road & Track.

[doorgunner69]

Years ago I read of backyard geniuses thinking of turning their airpumps into superchargers, so why the heck not do it with electricity?

Never looked into how much power it would take to spin it, but I know it is a lot. Had a belt driven blower on my 94 Mustang, and it was a constant maintenance item to keep the belt tight enough to stop slippage. Obvious significant amount of power needed.

[Still Thinking]

How Electric Superchargers Went from Fantasy to Feasibility

Uh, I'm pretty sure those are called "blowers". Superchargers are mechanically driven inlet fans and turbos are exhaust-driven.

[doorgunner69]

Not to be a buzzkill, but they are pretty much identical on the air inlet and compression side. Only difference is in what drives them.

More to it than that, of course, but really only the drive is what is different.

[Still Thinking]

Right, that was my point. You’re not being a buzzkill. I was just pointing out that pumping inlet air electrically isn’t a new idea, not even if you call it by the wrong name.

[Axenolith]

I thought a lot of belt driven superchargers were roots style blowers?

[FreedomPoster]

That is correct. Almost all of them, if not all, in common use. Jag and Audi come to mind immediately.

[Moose4]

I own a Mazda 3 as referenced in the article; it doesn’t have i-Eloop, but I test drove a Mazda 6 that did. It’s a pretty sophisticated and clever regenerative system that adds 1-2 mpg to the car because when the capacitor is charged, that’s used to power the electrics (power steering, fan, accessories) and it takes the load off the engine. Now at $2700 for the whole tech package (you can’t get i-Eloop separately) it’ll take a looooong time to recover that cost with 2 extra mpg, not to mention I can’t imagine how expensive it would be to fix when it breaks. But it works and it’s available on mass-market cars in the $30k range. A fully loaded 3 with the tech package bumps $30k, which is really pricey for a compact, but worth it IMO, I love mine and think it’s a fantastic little car.

BTW you can’t tell the system is on the car, there’s only the slightest extra bit of engine braking when you let off the gas and the capacitor starts charging. Other than that it’s completely transparent.

I understand how something like the electric supercharger works in theory, but if you’re out on your favorite mountain road or on a track day really thrashing your car, I wonder if a regenerative system can pack enough juice into the cap to keep the supercharger going.

}:-)4

[Sgt_Schultze]

Way back in the last century, two brothers were trying to create a turbo electric car engine. These guys weren't a couple of goofs. Harold Rosen is the guy who figured out geostationary orbit for satellites and his brother was the brains behind Compaq. Their eventual downfall was that they were trying to resell their powerplant to car manufacturers, and they needed more money for development after sinking their personal fortunes into the job. Since car makers differentiate themselves by their performance,mother didn't find any help and eventually folded.

Their project had such promise, it's about time that somebody leased the patents and tried again to make a go of it.

Link to the project

Link to the company's obit.

[Cboldt]

Superchargers are approximately positive displacement devices, turbos are not.

[Cboldt]

Those patents are probably public domain by now. Anybody is free to practice them.

[762X51]

I’m not a big fan of turbocharged engines after replacing two of them on a Jeep Liberty diesel to the tune of $9000. They are mechanical parts and it’s not IF they fail but WHEN. Wonder what the owners of the Ford EcoBoost F150s will be saying when it’s time to replace TWO turbochargers. They haven’t been in use long enough for the warranties to expire but I predict a glut of used ones on the market in about 2 years. The internal combustion engine peaked in 1965 with the introduction of the 4.9L inline 6. It had a good run of over 30 years.

[doorgunner69]

Some superchargers are positive displacement, many are centrifugal, identical to turbochargers.

There are advantages to both, and disadvantages.