For many years, governments have driven the improvement of fuel
economy in transportation through tightening legislation. This
effort has focused on passenger cars, but is increasingly concerned
with heavy-duty vehicles (HDV). The combination of this regulatory
focus with the ever present desire for low cost of ownership in
commercial vehicles is giving increased pressure to deliver more
fuel efficiency from the lubricants.
In order to deliver improved fuel efficiency, suitable test
methodology is needed to give repeatable discriminatory results
that not only help in the advance of technology, but can also
highlight the magnitude of the benefit expected in real-world
applications. Typical on-road driving has significant variation in
fuel consumption due to driver inconsistency, changes in rolling
resistance and changeable ambient conditions. In order to avoid the
effect of such variables, current practices, such as the EPA
SmartWay™ methodologies typically utilize gravimetric measurement
of removable fuel tanks or more recently the possibility of using
Portable Emissions Measuring Systems (PEMS) over a set cycle.
These methods do still have significant variability inherent
within them, and, therefore an alternative methodology has been
developed using Brake Specific Fuel Consumption (BSFC) in an
operating vehicle in order to measure fuel consumption in a more
repeatable manner. This paper describes the development process
that allows this measurement to be undertaken on a vehicle being
driven over a set cycle and discusses benefits relative to current
methodologies.