For 2019, the Ram 1500 pickup truck adopts a 48-volt starter-generator system to help improve fuel economy for the 5.7-L "Hemi" V8 (image: FCA).

Powertrain analyst: light-vehicle fleet needs big gains to meet tightening emissions regs

As American drivers increasingly show a preference for light trucks instead of cars, one widely known industry powertrain researcher and analyst warns the auto industry is on a path towards non-compliance with near-term federal fuel-economy and emissions regulations.

At SAE International’s 2018 High-Efficiency IC Engine Symposium in Detroit, Greg Pannone, president of Novation Analytics, showed data to indicate the efficiency of the U.S. vehicle fleet will need to improve at three times the rate it did in the last 12 years if it is to comply with federal greenhouse-gas (GHG) emissions regulations—standards that effectively stipulate fuel economy—for the 2017-2021 model years. Currently, he added, only about 6% of today’s vehicles designated as light-duty trucks would comply with the 2021 “footprint”-based GHG emissions standards.

“The light-truck fleet has been struggling since 2012,” Pannone said, adding that the 2016 model year marked the first time the broad auto industry did not comply with fleetwide average emissions standards, needed “banked” emissions credits to comply with the Phase 1 of the standards in effect for the 2012-2016 model years.

Pannone’s Novation Analytics research and consulting firm uses a metric it calls “tractive efficiency” to measure the relative efficiency of vehicle powertrains, controlling for other efficiency-related aspects of light-vehicle design such as mass, aerodynamics, rolling resistance and other factors. He said that although light vehicles are making steady and meaningful progress in improving tractive efficiency, the current pace of improvement will fall short of federal Phase 2 emissions regulations governing the 2017-2025 model years.

Like other speakers at the High-Efficiency IC Engine Symposium, Pannone acknowledged that although U.S. Environmental Protection Agency recently indicated it intends to ease the regulations affecting the 2022-2025 model years (see https://www.sae.org/news/2018/03/epa-to-ease-vehicle-emissions-standards), there is at the moment no certainty about the outcome of the EPA’s intent.

The top 1%

Without banked credits, Pannone said, in 2021 the industry fleet average would need to equal the tractive efficiency of the top 1% of current powertrains to comply. According the Novation’s measure, the top current powertrains have a tractive efficiency of about 25.5%, compared with industry-leading stated thermal efficiencies of around 40%.

Nonetheless, “we do see 2021 (fleetwide compliance) as very doable,” Pannone said, adding that currently available technologies, if deployed at higher penetration, is projected to make possible fleetwide compliance. The 2021 year is a watershed because it is the last year that does not fall under the purview of the 2017-2025 standards’ “midterm review” that allows the EPA to revise the standards for the 2022-2025 model years if it deems the regulations are too stringent or unachievable.

Many current technologies are being adopted at a comparatively rapid pace. Pannone said some 55% of all 2017-model light vehicles in the U.S. were fitted with direct-injection engines; the ratio is up from 22.4% in 2012. Stop-start technology appeared in about 18.5% of vehicles in 2017 compared with just 0.8% in 2012. And turbocharged engines were fitted to about 23.3% of all vehicles in 2017, Pannone said, compared with just 8.4% in 2012.

Pannone said at the current pace, GHG banked credits will be depleted by 2021 and the overall vehicle fleet will need substantial increases in the penetration of electric vehicles to achieve the existing 2025 GHG standard.

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