Semi-Volatile Organic Compounds from a Combined Dual Port Injection/Direct-Injection Technology Light-Duty Gasoline Vehicle

Gasoline direct injection (GDI) has changed the exhaust composition in comparison with the older port fuel injection (PFI) systems. More recently, light-duty vehicle engine manufactures have combined these two technologies to take advantage of the knock benefits and fuel economy of GDI with the low particulate emission of PFI. These dual injection strategy engines have made a change in the combustion emission composition produced by these engines. Understanding the impact of these changes is essential for automotive companies and aftertreatment developers.

A novel sampling system was designed to sample the exhaust generated by a dual injection strategy gasoline vehicle using the United States Federal Test Procedure (FTP). This sampling system was capable of measuring the regulated emissions as well as collecting the entire exhaust from the vehicle for measuring unregulated emissions. For this study, the unregulated emissions included hydrocarbon speciation and semi-volatile organic compounds (SVOC) in the form of polycyclic aromatic hydrocarbons (PAH), nitro-polycyclic aromatic hydrocarbons (NPAH), and oxygenated PAH (Oxy PAH). This novel sampling system allowed the quantification of the particulate-phase SVOC as part of the particulate on filters and the semi-volatile phase SVOC collected by XAD resin on traps. These compounds typically occur at very low levels in the exhaust and were determined by a gas chromatography/mass spectroscopy (GC/MS) analytical method and a two dimensional gas chromatography procedure (GCXGC) with a time of flight (TOF) mass spectrometer. In addition, the vehicle was sampled both with and without aftertreatment to characterize the engine-out and tailpipe-out emissions for a dual fuel injection (combined GDI and PFI) vehicle. Engine-out emissions were determined to characterize the composition of the exhaust entering the aftertreatment, and the tailpipe-out emissions were measured to determine the concentration of SVOC entering the environment.