Delphi Powertrain Study Concludes 3-Cylinder Turbo Gasoline Direct Injection Engine Offers a High-Value NOx and CO2 Solution for Cost-Sensitive Vehicle Segments

CO2 reduction potential vs. OEM On-cost for turbocharged GDi and turbo-Diesel technologies to meet Euro 6 standards. Source: Kirwan et al. Click to enlarge.

For the most cost-sensitive vehicle segments—e.g., compacts under 1,400 kg in weight—a stoichiometric 3-cylinder turbocharged gasoline direct injection (GDI) engine offers an optimal combination of cost, lower emissions and reductions in fuel consumption, according to an analysis by Delphi Powertrain presented at the recent SAE 2010 World Congress. (Earlier post.)

The Delphi study assessed the technology of downsizing and turbocharging; GDI
fueling and its synergies with turbocharging; and an analysis
of downsized 3-cylinder versus 4-cylinder engines. It also performed a value analysis comparing CO₂ benefits for 3- and 4-cylinder gasoline and diesel
powertrains.

Turbocharged stoichiometric GDi engine schematic. Source: Kirwan et al. Click to enlarge.

Vehicle electrification was outside the scope of the
analysis, Kirwan et al. said, noting that they expected that both the widespread implementation of stop-start technology and hybrid vehicle growth would continue. These technologies complement diesel and gasoline powertrains, and their implementation does not
alter the analysis or conclusions on the engines themselves.

Both downsizing (reducing total engine displacement) and downspeeding (reducing engine speed through changes to the transmission and/or final drive ratio) are effective methods to meet vehicle power needs with reduced fuel consumption.

For a given vehicle power requirement at constant speed, a downsized engine operates
at increased BMEP (specific load), which results in greater overall efficiency and thus reduced fuel consumption. Maintaining a given vehicle power requirement at reduced
engine speed also requires that the engine operate at higher specific loads, again resulting in greater overall efficiency and reduced fuel consumption.

The combination of the two, Kirwan et al. note, is particularly
effective for reducing fuel consumption and CO₂ emissions