Evolution of Light-Duty Gasoline Compression Ignition (LD-GCI) for High Efficiency and US Tier3- Bin30 Emissions 2024-01-2092

It is widely recognized that internal combustion engines (ICE) are needed for transport worldwide for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieve demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco’s PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing.

Test data showed that part-load fuel consumption was reduced 7 to 10 percent relative to a competitive 2.0L European diesel engine. The GCI engine produced “near-zero” tailpipe emissions of NOx, smoke, HC, and CO at most warm operating conditions. At 1500rpm, the engine was capable of over 25bar BMEP, demonstrating excellent low-speed torque characteristics of the engine.

Cold transient tests were conducted on the US FTP75 drive cycle using a “virtual vehicle” test methodology. A real engine and aftertreatment system with controller were tested in combination with vehicle and transmission models. Measured fuel economy (mpg) was 61 percent higher than the baseline spark-ignited turbocharged engine in a large SUV vehicle. Hydrocarbon, carbon monoxide, and NOx and PM emissions were below the stringent US 2026 Tier3- Bin30 regulations. An electrically heated SCR catalyst was needed to meet NOx tailpipe targets.

In addition to room temperature cold starts, cold startability tests were conducted in a cold chamber down to -30 degrees C. Electric intake air heating combined with exhaust rebreathing provided robust cold starts without spark assistance.

When operated on commercial E10 gasoline, simulated life-cycle CO₂ emissions were reduced about 31 percent relative to the baseline. When operated on low carbon eGasoline, CO₂ emissions were reduced by an estimated 80 percent, which is competitive with various new energy vehicles (NEV) including battery electric vehicles. Overall, this work shows that GCI technology has evolved as an efficient, clean, and robust powertrain for future transport.