Potential Impacts of High-Octane Fuel Introduction in a Naturally Aspirated, Port Fuel-Injected Legacy Vehicle
Technical Paper
2020-01-5117
ISSN: 0148-7191, e-ISSN: 2688-3627
Sector:
Event:
Automotive Technical Papers
Language:
English
Abstract
In recent years there has been an increased interest in raising the octane level
of gasoline to enable higher compression ratios (CR) in spark-ignition engines
to improve vehicle fuel efficiency. A number of studies have examined
opportunities to increase efficiency in future vehicles, but potential impacts
on the legacy fleet have not received as much attention. This effort focused on
experimental studies on an engine using high-octane fuels without changing the
engine’s CR. Spark timing was advanced until maximum torque was reached or knock
was encountered for each engine condition, using each individual fuel to
maximize engine efficiency. Knock-limited conditions occurred as the output
brake mean effective pressure (BMEP) neared the maximum attainable output at a
given engine speed. Increasing research octane numbers generally enabled
knock-free operation under a greater number of operating conditions. Vehicle
modeling using Autonomie was used to project vehicle energy use, fuel economy,
and tailpipe CO2 emissions for the Urban Dynamometer Driving Schedule
(UDDS), the Highway Fuel Economy Test (HWFET), and the US06 cycle. Results show
that decreases in energy consumption of up to 2% for a small SUV are possible
through the use of a 97 RON fuel compared to a baseline using 91 RON fuel,
provided that the formulation of the fuel does not cause unanticipated
operational issues such as lower maximum BMEP. Greater improvements using
high-octane fuels are possible if the CR is increased, but there is no
opportunity to increase the CR in legacy vehicles. Thus, these vehicles realize
an improvement from increased octane rating in accordance with their ability to
spark advance to take advantage of a fuel with a higher octane rating. For the
modeled vehicle, improvements of up to 2% in volumetric fuel economy may be
possible through the use of a 97 RON fuel with the largest gains expected on the
US06 cycle. Fuel economy impacts are strongly coupled to the heating value of
the fuels in addition to changes in engine efficiency. Similarly, decreases in
tailpipe CO2 emissions are also achievable. However, simultaneous
improvements in energy consumption, fuel economy, and tailpipe CO2
emissions are not guaranteed and are dependent upon fuel formulation.
Topic
Citation
Sluder, S. and Perry, N., "Potential Impacts of High-Octane Fuel Introduction in a Naturally Aspirated, Port Fuel-Injected Legacy Vehicle," SAE Technical Paper 2020-01-5117, 2020, https://doi.org/10.4271/2020-01-5117.Data Sets - Support Documents
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Also In
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