Lubricating Oil Composition for LSPI Reduction
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Solution Overview
Problem
Current lubricating oil compositions for direct injection-spark ignition engines fail to effectively reduce Low Speed Pre-Ignition (LSPI) events, which can lead to engine failure, despite efforts to optimize fuel economy and reduce CO2 emissions.
Innovation Solution
A lubricating oil composition containing a combination of molybdenum-containing and boron-containing additives, with a molybdenum content of at least 150 ppm and a boron content of at least 150 ppm, is used to lubricate the crankcase of the engine, providing a synergistic improvement in reducing LSPI events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calcium detergent content is reduced to reduce LSPI events, then LSPI frequency is reduced, but detergent activity and total base number (TBN) performance may be compromised
Solution Approach 1:
The patent changes the chemical composition parameters by replacing calcium detergent with magnesium detergent and adding boron-containing additives. This parameter change maintains detergent activity and TBN performance while reducing LSPI event frequency, as magnesium-based detergents provide similar cleaning action with reduced LSPI propensity when combined with boron additives.
Solution Approach 2:
The patent creates a composite lubricating oil formulation combining magnesium detergent, boron-containing additives (such as borated dispersants or boron-containing compounds), and other standard lubricating additives. This composite formulation achieves synergistic effects where the combination of magnesium detergent and boron additives provides both detergent functionality and LSPI reduction, overcoming the limitation of calcium detergent reduction.
2Reliability
If ZDDP concentration is increased to reduce LSPI events, then LSPI frequency is reduced, but ash formation and catalyst damage increase
Solution Approach 1:
The patent changes the additive composition by replacing high ZDDP concentrations with magnesium detergent and boron-containing additives. This parameter change reduces LSPI events while avoiding the harmful ash formation and catalyst damage associated with high ZDDP levels, as magnesium-based detergents and boron additives do not form ash in the same manner as ZDDP.
Solution Approach 2:
The patent uses alternative additives (magnesium detergent and boron-containing compounds) that provide the necessary LSPI reduction without the long-term harmful effects of ZDDP. These alternative additives can be used in lower concentrations without causing ash formation or catalyst damage, effectively replacing the need for high ZDDP levels.
3Loss of energy
If engine operating speed is reduced to improve fuel economy and reduce CO2 emissions, then fuel economy is improved, but LSPI events increase due to longer compression stroke time
Solution Approach 1:
The patent changes the lubricating oil composition parameters by incorporating magnesium detergent and boron-containing additives, which modify the combustion characteristics and reduce LSPI propensity. This allows the engine to operate at lower speeds for improved fuel economy without experiencing increased LSPI events, as the modified oil formulation prevents auto-ignition of oil droplets during the extended compression stroke.
Data Source
Figure 1
AI summary
A method of reducing low-speed pre-ignition (LSPI) in a direct-injected spark-ignited internal combustion engine comprising lubricating the crankcase of the engine with a composition comprising a combination of a molybdenum-containing additive and a boron-containing additive. Preferably, the composition comprises a calcium detergent providing a calcium content of at least 0.08 wt.%, based on the weight of the lubricating oil composition.