A vehicle test program was conducted to investigate the potential of combining several performance related evaluations into the California Air Resources Board (CARB) and Environmental Protection Agency (EPA) (proposed) 16,093-km intake valve deposit protocol. The 16,093-km (10,000-mile) tests, conducted with BMW 318i vehicles, were utilized to assess the gasoline- related effects on port fuel injector (PFI) flow, intake valve deposits (IVDs), octane requirement increase (ORI), combustion chamber deposits (CCDs), and oil viscosity increase (OVI).
The test matrix was based upon four 1985 BMW 318i vehicles and four fuels. The four-fuel set consisted of three commercial gasolines and one pure chemical, iso- octane. Each of the four cars was tested on each fuel.
During each 16,093-km test phase, the octane requirement and physical condition of the engine oil were evaluated. Upon completion of each phase, the cylinder head was removed and combustion chamber and piston top deposits were removed and weighed.
Thermogravimetric analyses were conducted on the intake valve deposits. The effect of engine operating parameters on the results, over a range of ambient temperatures, was also investigated.
Results of the program demonstrated that the 16,093-mile BMW test is a valuable tool to assess more than IVD characteristics of a gasoline. In this program, it was shown that the gasoline and/or engine oil affected octane requirement, combustion chamber deposits, and engine oil viscosity consistently. No significant effect of gasoline on the fuel injector performance was shown.