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Modern SI Engine Control Parameter Responses and Altitude Effects with Fuels of Varying Octane Sensitivity
Technical Paper
2010-01-1454
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
It has been shown that modern spark-ignition engines exhibit greater resistance to auto-ignition for fuels with increased octane sensitivity (RON − MON). This is often presented in terms of the Octane Index, OI = RON − K(RON − MON) with modern engines generally correlating with negative K values. Most of the studies have either presented detailed research type engine tests which show directly the impact on knock limited spark advance (KLSA), or have shown overall vehicle performance benefits and thus have inferred the KLSA response to OI. The aim of this research was to directly measure and compare the actual responses of various engine control parameters of modern production vehicles having different technology levels, to fuels with different OI values derived through different sensitivities. Comprehensive testing was performed at an altitude of over 1500 metres and confirmatory testing performed near sea level.
Five different fuels - comprising one Primary Reference Fuel (PRF) blend, one Toluene Standard Fuel blend and three full boiling range, multi-component fuel blends resulting in sensitivities ranging from 0 to 12.3 - were evaluated. Seven different vehicles including two naturally aspirated Port Fuel Injected (PFI), a turbocharged and intercooled PFI and four turbocharged and intercooled Direct Injection Spark Ignition (DISI) vehicles were used for the evaluation. Engine performance in terms of vehicle acceleration (50 to 110 km/hr) was measured while simultaneously recording engine operating parameters such as ignition timing and boost pressure. Vehicle performance indicated that, as expected, the high sensitivity fuels provided performance benefits to the boosted and intercooled engines.
The naturally aspirated PFI vehicle was not obviously knock limited at the high altitude test site, while a different naturally aspirated vehicle tested at sea level was and indicated generally higher levels of ignition retard for the less sensitive fuels, although this trend did reverse at higher engine speeds. The boosted PFI vehicle (tested only at altitude) used ignition retard only to control knock except for the zero sensitivity fuel (PRF) for which boost was also reduced at mid engine speeds. The boosted DISI engines relied on both ignition retard and, to a lesser extent, boost to control knock. The boosted DISI engines compensated fully for altitude. At sea level, the zero sensitivity fuel produced consistently lower boost pressures than all of the other fuels in the boosted DISI vehicles throughout the speed range. However, an interesting phenomenon occurred at altitude whereby the zero sensitivity fuel resulted in significantly higher boost pressures during the initial part of the accelerations, moderating to lower boost pressures in the middle to higher vehicle speeds. This occurred for both the boosted DISI and boosted PFI vehicles. This is thought to be as a direct consequence of the higher exhaust enthalpy available for turbine work which would result from the retarded ignition timing and allowing a more rapid build-up of boost pressure prior to boost pressure control becoming active. The knock control strategies appeared to respond as expected, confirming that the higher sensitivity fuels provide greater resistance to knock in these engines.
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Citation
Bell, A., "Modern SI Engine Control Parameter Responses and Altitude Effects with Fuels of Varying Octane Sensitivity," SAE Technical Paper 2010-01-1454, 2010, https://doi.org/10.4271/2010-01-1454.Also In
References
- ASTM Standard “Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel,” December 2004
- ASTM Standard “Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel,” December 2004
- Kalghatgi, G.T. “Fuel Anti-Knock Quality - Part I. Engine Studies,” SAE Technical Paper 2001-01-3584 2001
- Kalghatgi, G.T. “Fuel Anti-Knock Quality - Part II. Vehicle Studies - How Relevant is Motor Octane Number (MON) in Modern Engines?,” SAE Technical Paper 2001-01-3585 2001
- Swarts, A. Yates, A. Viljoen, C. Coetzer, R. “Standard Knock Intensity Revisited: Atypical Burn Rate Characteristics Identified in the CFR Octane Rating Engine,” SAE Technical Paper 2004-01-1850 2004
- Yates, A.D.B. Swarts, A. Viljoen, C.L. “Correlating Auto-Ignition Delays And Knock-Limited Spark-Advance Data For Different Types of Fuel,” SAE Technical Paper 2005-01-2083 2005
- Kalghatgi, G.T. “Auto-Ignition Quality of Practical Fuels and Implications for Fuel Requirements of Future SI and HCCI Engines,” SAE Technical Paper 2005-01-0239 2005
- Kalghatgi, G.T. Nakata, K. Mogi, K. “Octane Appetite Studies in Direct Injection Spark Ignition (DISI) Engines,” SAE Technical Paper 2005-01-0244 2005
- Mittal, V. Heywood, J.B. “The Relevance of Fuel RON and MON to Knock Onset in Modern SI Engines,” SAE Technical Paper 2008-01-2414 2008
- Mittal, V. Heywood, J.B. “The Shift in Relevance of Fuel RON and MON to Knock Onset in Modern SI Engines Over the Last 70 Years,” SAE Technical Paper, 2009-01-2622 2009
- Yates, A. Bell, A. Swarts, A. “Insights Relating to the Autoignition Characteristics of Alcohol Fuels,” Fuel 89 1 83 93 2009 10.1016/j.fuel.2009.06.037
- Yates, A.D.B. Cilliers, C.T. “A Fundamental Study of the Relationship Between Altitude and Research Octane Number,” SAE Technical Paper 2002-01-1662 2002
- Yates, A.D.B. “Fleet Tests to Determine the Octane Response at Different Altitudes for Vehicles Equipped with Knock Sensors,” SAE Technical Paper 2003-01-2012 2003
- Bell, A. Stone, A. Harmse, B. “Investigation (Desk Top Study) into the Optimum Future Octane Grade Structure for South Africa,” Final Report for the Department of Minerals and Energy South Africa Stellenbosch Automotive Engineering July 2003