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However, TGDI technology is susceptible to an abnormal combustion phenomenon termed as Low Speed Pre-Ignition (LSPI) event. This event happens prior to the intended combustion, which causes the catastrophic engine damage. ...In this paper, advanced methods to handle the LSPI occurrence severity and component level advances in design robustness to avoid the engine damage are reported. ...In overall, the techniques related to engine design to predict the LSPI occurrence in terms of peak cylinder pressure (PCP) and number of events are summarized.

This combustion occurs when the engine is operating under high load and low speed conditions and has been named Low Speed Pre-Ignition (LSPI). LSPI has shown to be very damaging to engine hardware. Although LSPI is a random occurrence, engine oils, specifically engine oil additives, have been shown to directly impact LSPI propensity. ...Additionally, oil contaminants such as wear metals may also contribute to changes in LSPI propensity. In this paper, the concept of LSPI durability is introduced. LSPI durability is defined as the ability of an engine oil to minimize or eliminate LSPI, not only while the oil is fresh, but also over a relevant oil drain interval (ODI). ...This is now well-known within the industry and several engine tests have been developed and adopted to measure the ability of an oil to prevent LSPI propensity of an engine oil. Two examples are the proposed GF-6 LSPI test and General Motor’s Stochastic Pre-Ignition (SPI) test.

Mechanism of suddenly occurring behavior of low speed pre-ignition (LSPI) in boosted spark ignition (SI) engines was analyzed with various experimental methodologies. ...Endoscope-visualized 1st cycle of LSPI showed droplet-like luminous flame kernels as the origin of flame propagation before spark ignition. ...Also, it was confirmed that subsequent cycles of LSPI occur only after enough operation time. These results indicated that local accumulation of liner adhered fuel and saturation of oil dilution can be a contributing factor to the sudden occurrence of LSPI.

LSPI (Low speed pre-ignition) is a serious issue in highly boosted gasoline engines. The causes have been studied and lube oil affects the onset.

All changes that increase the propensity of LSPI. The low speed-high load operation envelope is limited due to LSPI. Hydrogen engines are also being explored, however, with such a low minimum enthalpy of ignition, LSPI is a major limitation to thermal efficiency. ...Low speed pre-ignition (LSPI) is a limiting phenomenon for several of the technologies being pursued as part of the low carbon agenda. ...Hydrogen engines are also being explored, however, with such a low minimum enthalpy of ignition, LSPI is a major limitation to thermal efficiency. Several techniques are utilized in this study to investigate physical and physio-chemical aspects of lubricant initiated LSPI.

Increasing numbers of vehicles equipped with downsized, turbocharged engines have been introduced seeking for better fuel economy. LSPI (low speed pre-ignition), which can damage engine hardware, is a potential risk of the engines. ...We reported that engine oil formulation affects frequency of LSPI events, and formulating magnesium detergents into oil is a promising option to prevent LSPI events. ...To establish technology to reduce friction in low viscosity oils while ensuring good LSPI prevention performance, effective use of molybdenum dithio-carbamate (MoDTC) with magnesium detergents was investigated, since MoDTC is known as one of the most effective friction modifiers to reduce friction under boundary lubricating condition.

Switching to completely all-Magnesium detergent and/or severely limiting the concentration of Ca in the engine oil have recently been proposed as potential means to reduce LSPI. In this work, we evaluate the impact of detergent type on LSPI performance as well as on other performance that the modern engine oil needs to deliver. ...This suggests that though a switch to an all-Magnesium formulation, or severely limiting the concentration of Calcium in the engine oil may help reduce LSPI in the relatively small fraction of vehicles in the car park susceptible to LSPI, the perceived benefits may be outweighed by the significant penalty on fuel economy incurred by all the vehicles in the car parc. ...Low Speed Pre-Ignition (LSPI), also referred to as Stochastic Pre-Ignition (SPI), Superknock or Megaknock is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged gasoline engines.

However, high specific torque levels, especially at low speeds, can lead to abnormal combustion phenomena such as knock or Low-Speed Pre-Ignition (LSPI). LSPI, in particular, can limit further downsizing due to resulting and potentially damaging mega-knock events. ...Herein, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events. Our research shows that: (1) oil composition has a strong impact on LSPI frequency and that LSPI frequency can be reduced through a carefully focused approach to lubricant formulation. ...Herein, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events.

LSPI is an important issue to enable and enhance the effect of downsizing in SI engines. Experimental work was carried out by using 4 cylinder turbocharged gasoline engine, attaching the extra supercharger to get a higher boost pressure. ...Many parameters of driving condition, engine specification and lubricants were studied and some of them were extracted as the major items which affect the possibility of LSPI. Coolant temperature and Calcium (Ca) additive to lubricant had strong effect on the frequency of LSPI. ...Coolant temperature and Calcium (Ca) additive to lubricant had strong effect on the frequency of LSPI. Combustion strategy of strong miller cycle and LPEGR were also studied and compared in very high BMEP condition.

Low speed pre-ignition (LSPI) in downsized spark-ignition engines has been studied for more than a decade but no definitive explanation has been found regarding the exact sources of auto-ignition. ...No single mechanism can explain all the occurrences of LSPI and that each engine should be considered as a particular case supporting different conditions for auto-ignition. ...However, if Dual Fuel combustion is less knock sensitive, LSPI remains one of the main limitations of low-end torque also for dual fuel engines. Indeed, in some cases, premature ignition of CNG can be observed before the Diesel pilot injection as LSPI can classically be observed before the spark in gasoline engines.

The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition. ...The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices.

In this study, in order to clarify the mechanism of preignition occurrence in highly boosted SI engine at low speed and high load operating conditions, directphotography of preignition events and light induced fluorescence imaging of lubricant oil droplets during preignition cycles were applied. An endoscope was attached to the cylinder head of the modified production engine. Preigntion events were captured using high-speed video camera through the endoscope. As a result, several types of preignition sources could be found. Preignition caused by glowing particles and deposit fragments could be observed by directphotography. Luminous flame was observed around the piston crevice area during the exhaust stroke of preignition cycles.

The authors investigated the reasons of how a preignition occurs in a highly boosted gasoline engine. Based on the authors' experimental results, theoretical investigations on the processes of how a particle of oil or solid comes out into the cylinder and how a preignition occurs from the particle. As a result, many factors, such as the in-cylinder temperature, the pressure, the equivalence ratio and the component of additives in the lubricating oil were found to affect the processes. Especially, CaCO3 included in an oil as an additive may be changed to CaO by heating during the expansion and exhaust strokes. Thereafter, CaO will be converted into CaCO3 again by absorbing CO2 during the intake and compression strokes. As this change is an exothermic reaction, the temperature of CaCO3 particle increases over 1000K of the chemical equilibrium temperature determined by the CO2 partial pressure.

Calcium, which is used to ensure detergency and anti-rust performance, is reported to increase LSPI events. Therefore, new formulation technologies are needed to satisfy both LSPI prevention performance and other conventional performance areas. ...Engine oil formulation is known to affect low speed pre-ignition (LSPI), which creates technical restrictions on downsized turbocharged engines. Calcium, which is used to ensure detergency and anti-rust performance, is reported to increase LSPI events. ...The authors focused on two approaches: enhancement of LSPI prevention performance by adding a booster component and substitution of calcium for a less reactive component to balance performance areas including LSPI prevention.

To understand how the lubricant and fuel impacts on LSPI interact, a series of LSPI tests were performed with a matrix which combined fuels and lubricants with a range of LSPI activity. ...Fuels with high aromatic content or higher distillation temperatures have been shown to increase LSPI activity. The results have also shown that oil additives such as calcium sulfonate tend to increase the occurrence of LSPI while others such as magnesium sulfonate tend to decrease the occurrence. ...The results have also shown that oil additives such as calcium sulfonate tend to increase the occurrence of LSPI while others such as magnesium sulfonate tend to decrease the occurrence. Very few studies have varied the fuel and oil properties at the same time.

Additionally, increased aromatic content uniformly led to increased LSPI rates. For all blends, lower T90 temperatures resulted in decreased LSPI activity. The correlation between fuel octane (as RON or MON) suggests that octane itself does not play a role; however, the sensitivity of the fuel (RON-MON) does have some correlation with LSPI. ...To better understand real fuel effects on LSPI, a matrix was developed to vary certain chemical and physical properties of gasoline. The primary focus of the study was the impact of paraffinic, olefinic, and aromatic components upon LSPI. ...The primary focus of the study was the impact of paraffinic, olefinic, and aromatic components upon LSPI. Secondary goals of this testing were to study the impact of ethanol content and fuel volatility as defined by the T90 temperature.

There exists a relationship between the particulate number (PN) in the normal combustion and the LSPI frequency. The sensitivity of the PN to the LSPI frequency was approximately 2.0 times greater for the Mn-added gasoline than for the hydrocarbon-based gasoline. ...Gasoline-related factors that affect low-speed pre-ignition (LSPI) include the distillation properties of gasoline, manganese (Mn), ethanol, diesel fuel, detergent for aftermarket, and iron (Fe). ...Therefore, appropriate countermeasures for LSPI have not yet been implemented. To clarify the effect of the gasoline properties and additives on LSPI, engine tests were conducted using gasoline with different “PM Index” values, an indicator of distillation properties, different concentrations of Mn, ethanol, diesel fuel, detergent, Fe, and high-Ca oil.

The biggest challenge in developing Turbocharged Gasoline Direct Injection (TGDI) engines may be the abnormal combustion phenomenon occurring at low speeds and high loads, known as low-speed pre-ignition (LSPI). LSPI can trigger severe engine knocks with intensities much greater than those of spark knocks and thus characterized as super knocks. ...Based on findings in this study, it was proposed that the oil particles as oil loading in the blowby recirculation could be the root cause for LSPI as they cause dirtiness of the combustion chamber roof where the oil particles could be attached and then initiate LSPI in the late compression stroke. It was demonstrated that although LSPI may not be eliminated due to the nature of the triggers, TGDI engines can be operated super-knock free through controlling conditions for combustion and engine cooling. ...In this study, behavior and patterns of LSPI were investigated experimentally with a highly-boosted 1.5L TGDI engine. It was found that LSPI could occur as an isolated event, a couple of events in sequence, or a trail of events.

The effect of properties of lubricating oil on low speed pre-ignition (LSPI) was investigated. Three different factors of oil properties such as cetane number, distillation characteristics and Calcium (Ca) additive (with and without) are prepared and examined. ...Then actual engine test of LSPI was carried out to evaluate the effect and to clarify the mechanism and role of lubricating oil. ...Finally it is clarified that the oil cetane number and/or Ca additive strongly affect LSPI phenomena.

Recent investigations have reported that the auto-ignition of an engine oil droplet from the piston crevice in the combustion chamber may cause unexpected and random LSPI. This study shows that engine oil formulations have significant effects on LSPI. We found that the spontaneous ignition temperature of engine oil, as determined using High-Pressure Differential Scanning Calorimetry (HP-DSC) correlates with LSPI frequency in a prototype turbocharged DI-SI engine. ...Abnormal combustion referred to as Low Speed Pre-Ignition (LSPI) may restrict low speed torque improvements in turbocharged Direct Injection (DI) - Spark Ignition (SI) Engines. ...We found that the spontaneous ignition temperature of engine oil, as determined using High-Pressure Differential Scanning Calorimetry (HP-DSC) correlates with LSPI frequency in a prototype turbocharged DI-SI engine. Based on these findings, we believe that the oxidation reaction of the oil is very important factor to the LSPI.