DETROIT – When 54.5 mpg (4.3 L/100 km) corporate average fuel economy standards take effect in 2025, more than 90% of vehicles on U.S. roads will employ 8-speed transmissions and downsized turbocharged engines using direct fuel injection, an Environmental Protection Agency official says.

Likewise, turbochargers will gain power density as they grow in popularity for light-duty applications, says Edward Nam, director of the EPA’s Light Duty Vehicles & Small Engines Center in Ann Arbor, MI.

“We believe turbochargers will improve over time, and we believe engines will be able to improve over time,” Nam says at a CAFE seminar hosted here by powertrain specialist Ricardo during the recent SAE World Congress.

Nam says today’s turbochargers generally are limited to 261 psi (18 bar) of brake mean effective pressure, but that 348-psi (24-bar) units will be in the market by 2016 and used widely by 2025.

Also by 2025, Nam says 392-psi (27-bar) turbochargers are on the horizon, enabling engines to be downsized even further.

“So that means that a vehicle like a Ford F-150 or Chevy Silverado (pickup truck) being run with a 4-cyl. engine,” he says.

High-output turbocharged I-4 engines already are expanding applications in midsize and luxury cars and even midsize cross/utility vehicles such as the 7-passenger Ford Explorer.

A V-8 was available in the Explorer as recently as the ’10 model year, and nearly a quarter of Explorer buyers picked the V-8 in ’97 models, according to WardsAuto data.

The Explorer demonstrates the migration of downsized engines, although the take-rate for the 2.0L EcoBoost 4-cyl. was a relatively low 6.5% for the last model year.

Smaller engines will mean reduced fuel consumption, and Nam says the regulation should save 4 billion barrels of oil and slash greenhouse-gas emissions by 2.2 billion tons (2 billion t) between 2017 and 2025.

That translates to lifetime fuel savings for consumers of between $5,700 and $7,400, assuming 2025 gas prices of $3.87 a gallon, Nam says. If gas prices go higher, so would the savings, he suggests.

“The benefits of the program are massive,” Nam says, pegging them between $326 billion and $451 billion.

The technologies enabling vehicles to achieve 54.5 mpg in 2025 should push up the cost to produce a new vehicle by about $1,800, compared with 2016 levels, he says. But the payback period should be less than 3.5 years, thanks to savings at the pump.

The overall cost of compliance for the industry is expected to be as high as $136 billion, he says.

“We believe most auto makers should be able to meet the standards largely through advancements in internal-combustion engines and improvements in emissions. There’s a wide range of technologies available to help meet the standards.”

In addition to powertrain advances, Nam says aerodynamic gains, further development of diesels, more efficient accessories and low-rolling resistance tires also will reduce fuel consumption.

Auto makers will continue efforts to electrify their fleets, but Nam says the EPA forecasts less than 3% of new vehicles will be all-electric or plug-in hybrids by 2025.

On the other hand, growth rates are expected to be more robust for mild-hybrid vehicles with stop/start systems. That segment is expected to reach 7% in 2021 and nearly 27% in 2025, Nam says.

The 2025 target may sound daunting, but he says each auto maker’s actual fleet requirement will vary that year depending on its footprint distribution, roughly the area inside the four wheels. The smaller the footprint, the higher the mandatory fuel economy.

For instance, the Honda Fit subcompact with a footprint of 40 sq.-ft. (3.7 sq.-m) has a fuel-economy target of 61.1 mpg (3.8 L/100 km), which equates to CO2 emissions of 131 g/mile.

But a Chevrolet Silverado with a footprint of 67 sq.-ft. (6.2 sq.-m) has a more modest bogey of 33 mpg (7.1 L/100 km), which equates to carbon-dioxide emissions of 252 g/mile.

Nam credits Ricardo for its role in helping the EPA run about 200,000 full-vehicle simulations that formed the technical backbone of the regulation. The simulations allowed the EPA to project the most cost-effective way to meet the future standards.

“We relied on Ricardo’s global technical expertise to develop a new methodology,” Nam says. “It was truly a massive study.”

Ricardo validated and calibrated the EPA’s “Lumped Parameter” model to assess vehicle technologies that would help auto makers meet the 2025 standard.

“This is what we used to generate tens of thousands of vehicle parameters on which we chose our primary analysis of the feasibility of the rule,” Nam says. “With Ricardo’s data visualization, this approach was documented and the results were critical.”

tmurphy@wardsauto.com