Turbos Give Small Car Engines a Big Boost
This month, 33 cars will start the 101st Indianapolis 500 motor race. While each will sport a different color scheme, they’ll all share something in common. Every vehicle will be equipped with a turbocharger to boost engine performance.
Turbochargers have been used on race cars for decades. They’re also commonly used on heavy-duty trucks to improve operating efficiency and on sports cars to add extra power.
But, turbochargers are starting to appear under the hood of more mundane passenger cars. That’s because the devices are a cost-effective way to improve fuel efficiency. Turbos can help a four-cylinder engine produce as much power as their bigger V-6 counterparts.
It’s part of an ongoing trend toward engine downsizing. Automotive engineers are eager to harness the advantages of turbo technology to improve fuel efficiency and reduce emissions.
Turbochargers are centrifugal compressors powered by exhaust gas. They increase efficiency by forcing extra air into internal combustion engines.
Passenger vehicles equipped with turbocharged engines made up only 8 percent of the market in 2010, but that number has been rising steadily. In fact, by 2020, LMC Automotive predicts that more than one-third of all light vehicles will contain turbochargers.
IBISWorld says ongoing fuel-efficiency regulations are driving that demand. The market research firm claims that turbos will experience 3 percent annual growth between now and 2022.
That’s good news for Tier 1 suppliers such as BorgWarner, Continental and Honeywell, which produce the majority of turbochargers. Another supplier that hopes to cash in on growing demand for turbochargers in the North American market is Mitsubishi Heavy Industries Ltd. The company recently opened a new assembly plant in Franklin, IN.
“As emission regulations continue to tighten, mature automotive markets like the United States…are turning to turbochargers to help provide cleaner transportation,” says Olivier Rabiller, president and CEO of Honeywell Transportation Systems. “This is creating what we refer to as the golden age of turbo.
“With the ability to improve emissions and fuel economy by 20 percent to 40 percent in gas and diesel engines, turbocharging technology is a smart choice for helping automakers meet tougher global emissions standards without sacrificing performance,” claims Rabiller.
“In North America, more engine downsizing is expected,” adds Rabiller. “The current average engine size is a 3.0-liter six-cylinder. As the region continues to shift from larger naturally aspirated engines to smaller turbocharged ones, [our engineers are] working to provide more twin-scroll turbo technology support, which extracts more energy from four-cylinder exhaust profiles.”
Engineers are experimenting with advanced materials that can withstand higher exhaust gas temperatures and reduce weight, such as such as titanium aluminide and high-strength plastics like nylon. They’re also changing the inflow angle and speed of turbine wheel inlets.
Future turbocharger systems will also have to overcome new emissions constraints that may prevent engines from using scavenging, a strategy that adjusts engine valve timing to improve low-end torque.
According to Hiroshi Ataka, manager of Japan component forecasts and analysis at IHS Markit, the goal is to develop new types of turbochargers that can improve aerodynamic efficiency, reduce heat loss and reduce friction.
“[Lately, there’s been increasing demand for] smaller turbines and compressors to minimize the so called turbo lag (delay of the response),” says Ataka. “That’s because the exhaust gas power from small displacement, downsized engines is less than bigger displacement engines.
“Smaller turbines and compressors also need to be more durable to withstand higher revolution speeds than before,” Ataka points out. “The latest trends are aluminum compressors, electric superchargers and variable geometry turbochargers.”
Earlier this year, BorgWarner unveiled a line of variable turbine geometry turbochargers for a broad range of gasoline-powered vehicles. They feature an electric actuator that controls the pressure upstream of the turbine, rapidly and precisely adjusting the guide vanes for nearly instant acceleration and optimum power output. Patented S-shaped guide vanes regulate the turbine output, improving thermodynamics and engine response.