Intensified Emissions Testing Reveals Shortcomings of Downsized Engines
NOx, CO2, Particulates All Higher Than Initially Assumed
Engine downsizing has been the predominant trend in the automotive industry over the last decade, ranging from small compacts in Europe to fullsize trucks in North America. The assumption had been that a turbocharged, downsized engine would operate more efficiently in most conditions, better meeting government-mandated fuel economy and emissions standards, while delivering the level of power and performance customers expected. The reality of engine downsizing has been more of a mixed bag in the real world, with fuel economy often falling short of expectations or EPA figures. According to a Reuters report, closer emissions testing scrutiny in the wake of the Volkswagen diesel emissions cheating scandal, reveals that downsized engines, both gas and diesel, are bigger polluters than previously thought.
At higher load and throttle levels than standardized emissions lab testing, downsized gasoline direct-injected (GDI) turbos were found to emit up to 15 times more NOx emissions than allowed, along with higher levels of particulates and CO2. To mitigate the tightening standards expected by 2019, many automakers are planning on increasing the displacement of their future engines, potentially lowering peak combustion temperatures and cylinder pressures, two factors believed to be major contributors to NOx and particulate emissions. Volkswagen has also recently pledged to add a particulate filter to its future turbo GDI engines, an emissions control device previously only used on diesel engines.
In the fullsize truck market, Ford and General Motors have taken dramatically different approaches in engine development, with Ford aggressively pursuing engine downsizing on the F-150 with the introduction of the 3.5L and 2.7L EcoBoost V-6 models. GM has stuck with naturally aspirated, larger-displacement V-6 and V-8 engines with cylinder deactivation to achieve higher fuel economy targets. Many industry watchers believe the future trend will be slightly larger-displacement engines combined with a hybrid propulsion system to meet future fuel economy and emissions standards. Taking things a step further, some see this as a hastening of the era of full electrification of the automobile. What do you think truck powertrains will look like a decade from now?