Calcium Detergent Ratios for LSPI Suppression

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Solution Overview

Problem

Boosted internal combustion engines experience low-speed pre-ignition (LSPI) events, which are difficult to identify and suppress due to their sporadic and uncontrolled nature, causing engine degradation and damage.

Innovation Solution

A lubricating oil composition containing greater than 50 wt.% base oil of lubricating viscosity, combined with overbased calcium sulfonate and phenate detergents, and a specific calcium to nitrogen ratio, effectively reduces LSPI events by lubricating the engine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional lubricants are used in boosted internal combustion engines, then normal lubrication is provided, but low-speed pre-ignition events occur causing engine degradation and damage

Engineering Contradiction:

Improveengine reliabilityVSAvoidLSPI events

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical parameters of the lubricant by specifying a particular ratio of calcium from overbased calcium sulfonate to calcium from overbased calcium phenate (greater than 1.20 to less than 1.51), and a ratio of total nitrogen to total soap weight percent (greater than 2080). These parameter changes in the lubricant composition effectively reduce LSPI events while maintaining engine reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite additive package combining overbased calcium sulfonate detergent and overbased calcium phenate detergent in specific proportions within the lubricant base oil. This composite material approach creates a synergistic effect that reduces LSPI events better than individual additives alone

Inventive Principle:

Principle #40Composite materials

2Reliability

If LSPI events are suppressed through engine design modifications, then pre-ignition is reduced, but engine complexity increases

Engineering Contradiction:

Improvepre-ignition suppressionVSAvoidengine design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces the lubricant as an intermediary substance between the engine components and the combustion process. The specific calcium-containing detergent composition in the lubricant acts as a mediator that suppresses LSPI events without requiring modifications to the engine design, thereby avoiding increased device complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If calcium detergent amount is increased to reduce LSPI, then pre-ignition suppression improves, but total base number contribution increases

Engineering Contradiction:

ImproveLSPI reductionVSAvoidtotal base number

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent optimizes the parameter distribution by specifying that the total base number contribution from all detergents remains less than 4.2 mg KOH/g of the lubricating oil composition, while maintaining the specific calcium ratio (greater than 1.20 to less than 1.51) between overbased calcium sulfonate and overbased calcium phenate. This parameter optimization achieves effective LSPI reduction without excessive base number increase

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The lubricating oil composition achieves a significant reduction in LSPI events, with a 50% or greater reduction in LSPI counts during 25,000 engine cycles, while maintaining a high calcium detergent amount, thus enhancing engine performance and longevity.

Implementation Method 1

One theory suggests that auto-ignition of engine oil droplets that enter the engine combustion chamber from the piston crevice may be one cause of LSPI events. Accordingly, there is a need for engine oil additive components and/or combinations that are effective to reduce or eliminate LSPI in boosted internal combustion engines.

Methodology Applied

Scientific EffectAuto-ignition inhibition:

Data Source

PatentEP3571268B1Lubricants with calcium-containing detergents and their use for improving low-speed pre-ignition

Publication Date: 2022.07.13 AFTON CHEMICAL CORPORATION

AI summary

A lubricating oil composition and method of operating a boosted internal combustion engine. The lubricating oil composition includes greater than 50 wt.% of a base oil, one or more overbased calcium sulfonate detergent(s) and one or more overbased calcium phenate detergent(s). The calcium, boron, nitrogen, and amount of soap are maintained within certain ratios, and the total base number contribution from all detergents to the lubricating oil composition is less than 4.2 mg KOH/g of the lubricating oil composition, as measured by the method of ASTM D-2896. The lubricating oil composition and method may be effective to reduce low-speed pre-ignition events in a boosted internal combustion engine lubricated with the lubricating oil composition relative to capable lubricating oil compositions.