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Motor 1
9 hours ago
- Automotive
- Motor 1
The Brilliance of Electric Turbochargers
What is a turbocharger's job? In essence, it's to increase thermal efficiency. An electric turbocharger does this and more, which is why I'm a big fan. Thermal efficiency is a measure of how much of the potential energy of a fuel is consumed to create power, versus how much of it is simply generating waste heat. In pure terms, an automotive internal-combustion engine is not very efficient. For example, Toyota made a big deal in the late 2010s when it achieved 40 percent thermal efficiency in its Dynamic Force four-cylinder engine. Meaning it was only wasting 60 percent of its potential energy. Welcome to The Rabbit Hole , a bi-weekly column where Senior Editor Chris Perkins explores his latest obsession with automotive technology. He speaks to the best in the business to understand how cars work and what the future of the automobile looks like. Incidentally, this is why EVs have an appeal beyond zero local emissions. Thermal efficiency doesn't apply to electric motors because they're not directly powered by a heat source. But in terms of electrical efficiency—the ratio of electrical energy a motor consumes to its useful output—an EV's motor is about 75 to 90 percent efficient, according to Renault , at least. So, in short, internal-combustion engines, especially on their own, aren't especially energy efficient. Electric motors are very energy efficient. Turbocharging can help narrow that gap. Mind you, it's still a big gap, but any little bit helps, right? This story was available to our newsletter subscribers before it hit the site. Want early access? Sign up below. back Sign up For more information, read our Privacy Policy and Terms of Use . Turbocharging 101: A turbocharger consists of a turbine in the exhaust system, a compressor in the intake, and a shaft connecting the two. The exhaust turbine spins up with the flow of exhaust gases, which in turn spins up the compressor, increasing the density of the air headed into the engine, boosting power. In terms of thermal efficiency, it takes energy that would otherwise be lost as heat and turns it into something useful. Photo by: Mercedes-Benz Turbocharging 201: An electric turbocharger adds a motor attached to the shaft between the turbine and compressor. This means you can spin up the turbocharger independent of exhaust-gas flow, which has all sorts of benefits. Most notable is the all-but-elimination of turbo lag, but also the lowering of boost threshold, and allowing for higher boost pressure. And simply knowing the shaft speed of a turbocharger—which admittedly can also be achieved with a simple speed sensor—allows the automaker to run the turbo more safely closer to its maximum speed. But an electric motor works backward too, generating electrical energy if you use it to brake the turbine. An engineer from Mercedes-AMG once told me that in some cases, an electric turbocharger can be energy neutral ; The energy the turbocharger's motor regenerates is enough to power the turbocharger itself. There are big thermal efficiency gains to be had using electric turbochargers. Mercedes-AMG said in 2017 its electric-turbocharged Formula 1 V-6 exceeded 50 percent thermal efficiency , which was one of the first times ever an automotive engine converted more of its fuel source into useful power than waste heat. Like all F1 engines, the AMG V-6 uses a Motor-Generator-Unit-Heat (MGU-H), which is simply another term for an electric turbocharger. AMG later became the first to offer electric turbochargers in a road car with the four-cylinder in the C43 and C63. Photo by: Mercedes-Benz Porsche then took things a step further with its hybrid system for the new 911 Carrera GTS . Its single BorgWarner turbocharger has a 14.7-horsepower electric motor on its shaft, and uniquely, no wastegate. Typically, a turbocharger uses a wastegate—a valve that opens to expel excess exhaust gas—to limit boost pressure. Porsche instead brakes the turbocharger's motor to control boost pressure, so it's not wasting any exhaust gas and generating additional electrical energy. That additional electrical energy can power either the turbocharger itself, or the 53.6-horsepower traction motor sandwiched between the engine and transmission. Photo by: Chris Perkins / Motor1 A Porsche engineer also tells Motor1 that using a large turbocharger and limiting its turbine speed with the motor reduces exhaust-gas temperature, and therefore, the temperature of the charge air going into the engine. That eliminates the need for fuel enrichment, which is often used to reduce combustion temperatures, but this practice now being banned with Euro 7 emissions regulations. Porsche's use of an e-turbo boosts the engine's thermal and fuel efficiency, and overall vehicle efficiency. Broadly speaking, going electric feels like a natural extension for turbocharging. If the point of turbocharging is to boost efficiency, why not go for a solution that furthers that aim? Well, electric turbochargers are expensive, complicated, and heavy. Ferrari is using electric turbochargers for its F80 hypercar, but its closest rival, McLaren, uses conventional turbos in the coming W1. McLaren engineers told Motor1 that they didn't want the extra weight electric turbos would bring, and that they'd rather use the car's electrical energy to power the traction motor. Adding weight and complexity is always a difficult decision for an automaker, one of the many compromises it must consider in the course of engineering a car. The complexity has to justify itself. McLaren might also have a point on the electrical energy side of things. In the past, I've written about interesting internal-combustion engine technologies, like Mazda's spark-controlled compression ignition and Nissan's variable compression . Both improve efficiency and performance, but not so much as augmenting internal combustion with a conventional hybrid system. Does electric turbocharging fall into the same category? Someone from one automaker might say yes, but then why would engineering powerhouses like Mercedes, Porsche, and Ferrari all embrace it? Photo by: Porsche Ironically, for a technology that was developed in Formula 1, the sport will soon abandon electric turbocharging. To attract more engine suppliers, F1 is changing its engine formula for next year to abandon the MGU-H, deeming it too expensive and not relevant to road cars… just as more road cars are embracing this technology. F1 is also upping the electric portion of its hybrid powertrain to achieve about a 50/50 split between engine and motor power. And hey, F1 is expanding its engine supplier base with Audi, Ford, and GM all joining the fray. F1 is a sport and a business, not simply a technological proving ground. In any case, turbocharging is, in spirit, about not leaving energy on the table. An internal-combustion engine is going to produce a ton of exhaust gas that is pure waste. Why not make something useful out of that? And why not generate additional electrical energy from it while you're at it? Engineering at its best maximizes the potential of what you have in front of you. This isn't to say that cars that don't use electric turbochargers are bad, or that there aren't legitimate reasons to skip out on this piece of tech. It's possibly something that only justifies itself in higher-end performance-car applications. There's an admirable engineering ideal with electric turbochargers that satisfies the nerd in me. Isn't maximizing potential something we should all strive for? Further Down the Rabbit Hole Why Carbon-Ceramic Brakes Are Expensive. And Why They Might Be Worth It Why BMW's B58 Is a True Successor to the Toyota 2JZ Share this Story Facebook X LinkedIn Flipboard Reddit WhatsApp E-Mail Got a tip for us? Email: tips@ Join the conversation ( )
Yahoo
03-04-2025
- Automotive
- Yahoo
Electrified gasoline engines may be the powertrain of the future
In 1966, General Motors built the Electrovair II, an electric version of the Chevrolet Corvair packed with the latest technology from the aerospace and electronics industries. The car's acceleration nearly matched the 110-hp gasoline-fueled Corvair, but without the noise and vibration of a combustion engine. Still, the Electrovair II lacked the driving range and rapid fill of its gasoline sibling. In a promotional video, the narrator says: 'Electrovair II can only travel 40 to 80 miles depending on how you drive it before its silver zinc batteries must be recharged. Recharging takes almost six hours. Obviously, a better battery must be found to make a practical car, but Electrovair II has demonstrated for the first time what electric car performance could be like when that better power source is found.' Six decades later, scientists are still looking for that better battery — one that charges as fast as a pump fills a gasoline tank and propels the vehicle for well over 350 miles before recharging. Sign up for the weekly Automotive News Mobility Report newsletter for the latest developments at the intersection of transportation and technology. As Automotive News celebrates its 100-year anniversary, we are taking a look at today's topics through both a historic and future lens. This installment looks at the future of powertrains. The effort to displace gasoline as the primary fuel for automobiles is as old as the car itself. Steam, turbines that could run on anything from french fry grease to perfume, hydrogen and natural gas have all been looked at as replacements. Until recently, battery-electric vehicles looked to be the successor. But a flurry of announcements from various automakers in recent years saying they wouldn't invest heavily in new combustion engines has turned into a false alarm for those who like the roar and vibration from putting the pedal to the metal. Toyota is working to improve the thermal efficiency of its engines, a move that increases fuel economy and reduces emissions by converting more of the heat generated in the combustion process into work. Toyota's Dynamic Force engines can achieve 41 percent thermal efficiency. Most combustion engines run at about 30 percent efficiency. (EVs operate in the 70 percent range, according to the Department of Energy.) Porsche plans a combustion-engine SUV that could be a replacement for its gasoline Macan as the automaker boosts investments in gasoline models amid slower-than-expected EV sales. Mercedes-Benz said this year that is it developing a new combustion engine, a reaction to its tepid EV sales. But even as they start to invest in new engines, automakers are also looking at how to pair electricity with gasoline motors. 'I believe that the most cost effective gains can be made by modifying the internal combustion engine's operation through the use of electrification,' said Greg Davis, director of the advanced engine research laboratory at Kettering University in Flint, Mich. 'Internal combustion engines do not have broad regions of high efficiency, so combining them with electric drives in hybrid electric vehicles is a great way to limit the use of the engine to operating regions with better efficiency,' Davis said. The early Toyota Prius and Honda Insight were the first step in this direction. They used electricity to launch from a stop — the portion of the drive cycle that needs the most power — and then let the gasoline engine take over. What may emerge, at least in some global markets, is a permanent marriage between gasoline engines and electric motors. Even early tinkerers, including Ferdinand Porsche, recognized the benefits of electrifying the gasoline powertrain. In the early 1900s, Porsche installed electric wheel hub motors in a giant wagon called the Lohner-Porsche. That vehicle debuted in 1900 at the World Exposition in Paris. But the excessive weight of the 80-volt lead-acid batteries and electric motors severely limited driving range. On his next vehicle, the Mixte, Porsche added a gasoline engine to power a generator to recharge the batteries. It was the first range-extended hybrid. Fast-forward 125 years and the range-extended gasoline-electric powertrain that Porsche pioneered is on the cusp of making a comeback. Ram is launching the extended-range Ramcharger truck this year. Scout plans to offer a range extender in its SUVs and pickups. Ford CEO Jim Farley said a range-extender powertrain in the company's SUVs and pickups is coming in 2027. Nissan's e-Power engine, used in a range-extended vehicle sold overseas, achieves 50 percent thermal efficiency and will launch in U.S. versions of the Rogue in 2026. Mazda and Subaru are also working on a new generation of engines geared specifically for hybrid powertrains. And Mercedes-Benz's AMG division is working on a 'highly electrified' V-8. Davis believes we'll see electric motors not just bolted to a gasoline engine but integrated into its design. 'This also allows the use of smaller displacement engines, lowering costs, as the engine output can be combined with the electric output during transitory high-demand situations,' he said. Nonetheless, EVs are a potent challenger to the combustion engine's reign. EVs made up 8 percent of new-vehicle registrations in the U.S. last year, or 1.28 million vehicles, according to S&P Global Mobility. That was an 11 percent gain from the prior year and outpaced the 2.5 percent gain for all light-vehicle sales last year. Those vehicles all rely on forms of lithium ion battery chemistry. For most models, that allows a range of at least 250 miles, high-voltage charging in 45 to 60 minutes and easy overnight home charging. Two emerging battery chemistries, sodium ion and solid state, have the potential to replace today's lithium ion cells in most EVs, allowing them to match combustion engine convenience. Sodium ion batteries could be less expensive to manufacture because the raw materials they use are abundant. But lower power density and a shorter life are two major issues battery engineers are working to solve. Solid state batteries, which could be on American roads by 2030, promise faster charging, lower risk of fires and greater energy density. But solid state batteries have challenges, too. They are expensive to manufacture. In China on March 17, BYD announced that its Super e-Platform batteries can deliver 248 miles of range in just five minutes, bringing an EV into parity with the speed at which a gasoline-fueled car can be refilled. Chris Borroni-Bird, a research scientist who worked on fuel cell development at Chrysler and General Motors, said he sees a very different type of automobile on the road a century from today. Powertrains will be battery electric, getting most of their energy from solar panels, he said. Advanced wheel motors will improve maneuverability and provide greater design flexibility. The powertrain won't be the only part of the car with a smaller environmental footprint. 'Right-sized vehicles made of recycled and natural materials and having a solar panel roof can be used to complement public transport and make moving people and goods easier on the wallet and on the planet,' he said. Throughout 2025, we will honor our legacy by connecting topics of today with our historical coverage as we look ahead to the next 100 years. Have an opinion about this story? Tell us about it and we may publish it in print. Click here to submit a letter to the editor.
