So there is still some life left in gasoline engines?
Definitely. John Heywood, a professor of mechanical engineering at the Massachusetts Institute of Technology, predicts that in 2050, 60 percent of light-duty vehicles will still have combustion engines, often working with electric motors in hybrid systems and largely equipped with a turbocharger. Vehicles powered purely by batteries, he estimates, will make up 15 percent of sales.
The power-boosting advantage of turbochargers is widely deployed today, but in coming years it could be tilted toward the design of smaller engines that still meet customers’ needs. “The real benefit comes from downsizing,” Dr. Heywood said. “That reduces friction, which chews up a significant part of the energy input.”
Dr. Heywood, who has pondered whether he would best serve his students by teaching combustion or electrochemistry, addresses the challenge of gasoline’s future from a somewhat different direction: the practical limitations of battery electric cars. “Holding a gas nozzle, you can transfer 10 megawatts of energy in five minutes,” he said, explaining today’s refueling reality. To recharge a Tesla electric at that rate today, he said, would require “a cable you couldn’t hold.”
The question is how much better gas engines can get. Conventional piston engines have come a long way, and technical refinements like direct fuel injection, variable valve timing and cylinder shutdown systems are now widespread. Along with innovations in lightweight body materials and dual-clutch transmissions, mileage has steadily improved, so naturally, further gains are now harder to come by — usually in single-digit percentages.
Why won’t electric cars catch on faster?
That depends on what is meant by “electric.” In the United States today, only about a dozen new models run solely on motors powered by batteries; five times that many models in showrooms use some combination of a gasoline or diesel engine and an electric motor. These hybrids, some of which carry large batteries that can be recharged by plugging into grid power, can be very efficient. But because of the extra equipment, their initial cost is higher. Electrified cars of all types are selling briskly compared with previous years, but they are still a tiny portion of the total market in this country. In July, hybrids and electrics accounted for 44,000 sales in a total market of 1.4 million vehicles.
Even the plans in Europe to ban the sale of new gas- or diesel-powered cars will take decades to fully kick in. The rules would not take effect for more than 20 years. In addition, the average age of the 270 million light-duty vehicles on the road in the United States today approaches 12 years, so even if sales of new petrol-burning cars stopped immediately, it would take more than a decade for the fleet to switch over.
But cars like the Toyota Prius can still be more economical, right?
Hybrids like the Prius may continue to save money at each fill-up, but that’s not the whole story. In its test of the 2017 Chrysler Pacifica Hybrid minivan, a plug-in model that the government says can drive 33 miles on battery power alone, Car and Driver calculated the payback of the $2,100 hybrid premium to be more than eight years (based on driving 12,000 miles a year and before any tax incentives). So, yes, there are savings if you drive lots of miles or tend to hold on to vehicles for a long time. The calculus shifts if gas gets more expensive. That said, the hybrid is friendlier to the planet in terms of tailpipe emissions and greenhouse gases.
What else should we expect with engines further into the future?
By 2050, Dr. Heywood’s studies project, today’s fuel economy could be doubled. “A quarter to a third of that improvement would come from improvements to the vehicle,” he said, in areas like aerodynamics and weight reduction. Other promising areas include variable compression ratios — a technology Nissan plans to introduce next year — and making better use of available fuels.
That question of whether to teach combustion or electrochemistry? Dr. Heywood still wrestles with it, though he admits that the answer is “both of the above.” The topic has become the theme of a presentation he has prepared — and the concept of electrification can be found on most pages.