Date of Award


Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeffrey D. Naber

Committee Member 1

Mahdi Shahbakhti

Committee Member 2

Garlan Huberts


In this thesis, two different works related to cold start of a direct-injection (DI) gasoline engine are shown. First, effect of split injection is studied on engine exhaust temperature and hydrocarbon emissions for cold start conditions. Instead of single injection, two injections are done, one injection during the intake stroke and one injection during the compression stroke. Split injection is known to reduce jet wall wetting, thus reducing the hydrocarbon emissions from engine itself. Further, split injection reduces engine cycle-by-cycle variability with respect to the single injection case. Correlations between start of injection for the injection in the intake stroke (SOI), end of injection for the injection in the compression stroke (EOI) and Split Ratio (SR) with Exhaust Temperature (Texh) and engine hydrocarbon emissions are proposed with the help of design of experiments (DOE). These correlations could be used for controlling exhaust temperature during cold start. Second, because of repetitive marshalling of a vehicle, i.e. cold start the engine on the vehicle and drive it a few feet and then turn it off, spark plugs are observed to get fouled. A spark plug is considered to be fouled when the insulator nose becomes coated with a foreign substance including oil, fuel or carbon. This enables the ignition coil voltage to follow along the insulator nose and ground out rather than bridging gap and firing normally. A tool to measure quasi real-time spark plug fouling is proposed in this work, which uses in-cylinder ion data to measure offset voltage which is then used to calculate spark plug shunt resistance. Based on the spark plug shunt resistance, fouling level of the plug can be calculated, and the condition of the plug can be determined.