So the news is that International Lubricant Standardization and Approval Committee (ILSAC) has identified timing chains on direct injection engines to be inherently problematic. (not the tensioners) due to improper lubrication

They are proposing that some test be developed to measure the wear on the chain. And that wear number is going to be stated on the oil in the new GF-6A Specification. More importantly they want all oils to be able to control some degree of chain wear.

(chain wear has now been pinned on accumulation of contaminants in oil and dilution of oil by gasoline)

Its great news for some of us is that we were pointing out that timing chains on DI were lasting a third as long as conventional engines. Now its been confirmed.

No your mail-order oil test is not going to show this. But it can once the standard has been set.

No they dont say change your oil more frequently. Remember they are not talking to the public, this is for within the lubrication industry i.e oil manufacturers like castrol.

You can draw your own inferences as to what you can do to get a jump on things.


ILSAC To Add Timing Chain Wear Test To GF-6


Gasoline direct injection (GDI) and turbocharged GDI (GDI-T) engines are expected to capture 60 to 65% of the North American new passenger car market by 2019. GDI and GDI-T engines are headed for dominance and for good reason: better fuel economy, better torque, and better power from the same size engine versus indirect port fuel injection (PFI) engines. A turbocharged GDI engine can also be downsized and deliver the same peak power along with significantly better fuel economy.

Blue area is GDI forecast
Red area is PFI forecast
Source: HIS Global Insight
Compared to PFI engines GDI and GDI-T engines have several unique features:

1. increased production of fine carbon particulates during combustion which can enter the crankcase via blow by and cause excessive wear
2. increased fuel dilution of crankcase lube oil (cylinder wall wetting by side-mounted direct fuel injectors allows fuel to contaminate the lube oil)
3. increased oxidation and deposits from higher operating temperatures and pressures
4. higher initial cost than PFI engines for the higher-pressure fuel injection system

The one component that suffers the most from accelerated wear in GDI and GDI-T engines is the metal timing chain, which drives the camshaft(s) off of the crankshaft. Excessive wear can cause the check engine light to illuminate and could result in very expensive internal engine hardware repairs. Excess wear is evident in chain elongation which can disturb valve timing leading to degraded performance and higher engine out emissions. Researchers are not yet sure about the exact wear mechanism—it could be abrasive wear from carbon particles suspended in the lube oil or an interaction between carbon particles and the lubricant or both. A typical timing chain connecting the crankshaft and the overhead cams is shown below.

ILSAC has proposed a timing chain wear test for their new ILSAC GF-6 passenger car engine oil specification click here to view the draft specification proposed for first API licensing on 1/1/2017. Ford is developing the chain wear test in a 2.0 L I-4 EcoBoost GDI-T engine. The wear test procedure is proposed to assure that ILSAC GF-6 engine oils can meet the timing chain durability requirements in GDI and GDI-T engines.
The rest of the world is faced with the same challenge. The European Automobile Manufacturers Association (ACEA) is discussing the problem with counterparts in the oil and additive industry with a view of developing a suitable test in the furutre.
The timing chain is constantly facing unfavorable mixed and boundary layer lubrication regimes. Click video link below to learn more about boundary layer lubrication. Mixed and boundary layer lubrication regimes are not the ideal hydrodynamic lubrication regime where metal surfaces well separated by a protective oil film. GDI and GDI-T engine field experience shows in addition to timing chain wear more aggressive oxidation, viscosity gains, and related increases in varnish deposits. None of this is good, so improvements in lubricant performance is nessesary to enable the successful introduction of this new engine technology.
Lubrizol is developing high performance advanced additives packages for high performance GDI and GDI-T engine technology which will soon dominate the passenger car market. Lubricant additives can minimize wear, combat oxidation and control deposits. New lubricant chemical additives require development involving years of test results before commercialization. Given long lead times for lubricant product development, testing, and commercialization there is a growing urgency to proceed with the ILSAC and ACEA programs if the requested commercializations dates are to be met.




The Timing Chain-wear Test
Why? The Timing Chain-wear test is another brand new test and is being developed in response to new engine technology. Contaminants from combustion enter the lubricant sump as a result of blow-by and accumulate in the lubricant leading to increased chain wear. Also like the LSPI test, a Ford 2.0 liter EcoBoost engine will be used to run the chain-wear test.


What does the test accomplish? The test will effectively measure a lubricant’s ability to minimize timing chain-wear as it relates to the soot-like material particles produced by GDI engines.
How Lubrizol is staying ahead: Lubrizol is actively involved in the development of this test. The greatest challenge here involves accurately recreating the field severity of an engine dyno that accurately and repeatedly reproduces chain-wear.
In all, the inclusion of six new tests in the proposed GF-6 specification is a drastic change from that of older specifications, necessitating major investment from industry stakeholders. The implications for oil marketers are severe, and the new tests will require innovation and dedication to keep pace. Each test has its challenges, and through industry collaboration and innovation, those challenges will be met.

 

Looks to be from November 2013 ILSAC to Add Timing Chain Wear Test to GF-6 Specification | GF-6 | Lubrizol

Is Lubrizol a brand name or a company or what?

Similar articles from engine makers re their stretched/worn chains on GDI engines?

 

Ignore the name lubrizol. Focus instead on the ILSAC and ACEA

 

Tribology International
Volume 86, June 2015, Pages 77–84



Characterisation of soot in oil from a gasoline direct injection engine using Transmission Electron Microscopy

• A. La Roccaa, , ,
• F. Bonatestab,
• M.W. Faya,
• F. Campanellaa

Highlights

•Soot-in-oil particles extracted from used lubricating oil of GDI engines.
•Soot in oil shows modest branching with average length of 153 nm and 59 nm in width.
•Soot spherical primary particles of 10–90 nm form the agglomerates.
•Primary particles exhibit an amorphous shell structure of 5 nm.
•Volatile structures were found to be deposited onto the surface of primary particles.

Abstract

In this work, an investigation of soot-in-oil samples drawn from the oil sump of a gasoline direct injection (GDI) engine was carried out. Soot particulate was characterised in terms of size, distribution and shape of the agglomerates, and internal structure of the primary particles. The test engine was a 1.6 l modern light-duty EURO IV engine operated at speed between 1600 and 3700 rev/min, and torque between 30 and 120 Nm. After a double oil-flushing procedure the engine was operated for 30 h. Oil samples were drawn from the sump and prepared for Transmission Electron Microscopy (TEM) and High resolution TEM analysis (HRTEM) by a combination of solvent extraction, centrifugation and diethyl ether bathing. Soot agglomerates were measured in terms of their skeleton length and width, and fractal dimension. The mean skeleton length and width were 153 nm and 59 nm respectively. The fractal dimension was calculated using an iterative method and the mean value was found to be 1.44. The primary particles were found to be spherical in shape with some irregularities and presented an average diameter of 36 nm with a mode of 32 nm and standard deviation of 13 nm. The majority of particles showed an inner core and outer shell similar to diesel soot, although an amorphous layer was also clearly visible.

Keywords

• Gasoline soot;
• Lubrication oil;
• Nanoparticles;
• Transmission Electron Microscopy

1. Introduction

Gasoline Direct Injection (GDI) engines are considered an important source of carbonaceous nanoparticles; they produce higher levels of soot as the process of fuel vaporisation and gas-phase mixing remains essentially incomplete [1], even when early fuel injections are used to enable a homogeneous combustion mode [2] and [3]. This leads to the establishment of sub-stoichiometric mixture-pockets, which are thought to be a significant source of soot formation. Other important mechanisms leading to soot formation have been identified in recent years; primarily, the presence of liquid fuel film over cylinder/piston walls and consequent pool-fire [4] and [5], as well as the process of direct carbonisation of remaining liquid droplets [6]. The phenomenon of soot formation can be essentially described in terms of three steps: nucleation, growth and oxidation [7]. The process occurs under fuel-rich conditions, in both rich premixed and non-premixed flames, where the local equivalent ratio is more than one. The nucleation process takes place under high temperature conditions, between 1000 and 2800 K, with unburned hydrocarbons, in particular acetylene and polycyclic aromatics hydrocarbons (PAH), being pyrolysed and oxidised. The condensation reactions of these gas-phase species lead to the appearance of a large number of primary soot particles with diameter lower than 2 nm and insignificant soot loading. Surface growth, coagulation and aggregation represent the particles growth. During the surface growth, concentric shells on nuclei and spherules are formed by deposition of hydrocarbon intermediate gas-phase species on particles surface. By means of coagulation the particles collide and merge reducing their number concentration, but keeping the total amount of soot constant. After formation, the collision between particles leads to cluster or chain-like soot aggregates (secondary particles) in which the number of particles decreases with a consequent size increase (PM diameter 100–900 nm). In the overall soot formations process, the precursors, the nuclei and particles can be oxidised if in contact with oxidising species such as O2, O, OH, CO2, and H2O at the right conditions. Typically, HRTEM shows the primary particles having an outer shell composed of planar shaped crystallites orientated perpendicular to the radius of the particle. The crystallites are comprised of several PAH layers. An inner core, which is constituted by several fine spherules (3–4 nm in diameter) having a nucleus of 1 nm at the central portion, usually characterises primary particles.
The particle number concentration emitted by GDI engines are generally higher than conventional PFI engines and Diesel engines equipped with Particulate Filter (DPF). Most of the soot produced is expelled from the cylinder with the exhaust gases but a small proportion is transferred from the cylinder to the lubricating oil. Soot is likely to migrate into the oil film early during the expansion stroke [8]; consequently, the morphology, agglomeration and other characteristics of soot-in-oil are likely to be rather different to exhaust soot. Soot-in-oil has not been subject to oxidation processes to the same extent and hence the outer shell structure is more likely to remain intact. Although only a small proportion of the soot formed in the combustion chamber transfers to the engine oil, it contributes to the lubricant degradation. This is certainly a new challenge for the modern GDI engine as soot-in-oil raises concerns upon wear and engine durability. It is well established that oil thickening has a complex dependence on soot [9]. Various investigators [10] and [11] have shown that diesel soot build up in oil gives rise to increased engine wear rates; Gautam et al. [12] reported that wear increases with higher soot concentration. Soot reduces the effectiveness of anti-wear additives and its effect on wear depends upon the characteristics of the particles and agglomerates of soot. Abrasive wear occurs and wear scar width closely matches the primary particle size [10]. Oil thickening was found to enhance timing chain elongation due to abrasive action of soot on pins and bushing [13]. Bardasz et al. [14] studied the influence of high number of engine cycles on lubricant oil and that of oil characteristics on engine wear, comparing direct injection and port fuel injection engines and finding increased wear for the first category. There is also a growing interest within the automotive industry to better understand the complex interactions between soot morphology and properties of lubricating oil.
Studies of soot in automotive lubricant oil have mainly focused on particulate matter from diesel engines or carbon black. The percentage by weight of soot in automotive lubricants, assessed using thermo-gravimetric analysis (TGA), was identified as the primary correlation factor affecting oil properties and engine wear [15]. Fourier Transform InfraRed (FTIR) spectroscopy is commonly used to monitor used oil conditions, although this technique is not sufficiently quantitative [9]. Nanoparticle tracking analysis has recently been employed for the measurement of soot agglomerates size distribution and number density from automotive engines oils [16]. Transmission Electron Microscopy (TEM) and High Resolution TEM (HRTEM) are amongst the most widely used techniques available to characterise soot nanoparticles; TEM allows measuring the particle shape and size of projected two-dimensional images of agglomerates as well as the characteristics of individual particles. However, soot-in-oil TEM imaging is more challenging; mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam [17]; very limited information is available in the literature on this topic. Imaging by Cryogenic TEM has also been used by Kawamura et al. [18] and Liu et al. [19] to measure the soot agglomerates size although localised thick layers proved to be challenging and constituted a problem. Li et al. [11] have used solvent extraction technique and ultracentrifugation to prepare the specimen for conventional TEM to analyse soot primary particles from a heavy duty diesel test engine. Clague et al. [7] employed solvent extraction followed by centrifugation to extract soot from used engine oil. A recent study on soot agglomerates shows that centrifugation can alter the distribution of size and shape of these [20]. The solvent dilution technique gives sufficient separation of oil and soot to allow conventional TEM results to be obtained; centrifugation is necessary in the preparation of samples for HRTEM studies of primary particles; these are unchanged by centrifugation. TEM allows measurement of agglomerate size distribution; HRTEM allows examination of the structure and the distribution of the carbon sheets of the primary particles; it provides information about reactivity and nanostructure morphology. The form taken by the soot-in-oil is of interest because of the influence on oil properties, engine performance and wear and for insights into the history of particle formation and growth.

Engine soot and laboratory flame-generated soot is commonly described in terms of fractal dimension due to the complex morphology [21], [22], [23], [24] and [25]. Smaller fractal dimensions indicate chain-like structures while larger fractal dimensions indicate clusters. The fractal dimension is a statistical index of complexity and Rogak et al. [26] noted that agglomerate fractal dimensions measured from two-dimensional image projection of three-dimensional structures may be 10–20% lower than geometric dimensions. Given their irregular branched shape, soot particles are also characterised in terms of maximum projected length (L) and width (W) [26], [27] and [28]; for chain-like structures, Rogak et al. [29] suggested measuring the skeleton length (Lsk) of agglomerates.
Barone et al. [30] used TEM to investigate the diameter of aggregate primary particles from GDI exhaust gas soot. They studied particles morphology as a function of injection strategy. Early fuel injections, leading to a more homogeneous air/fuel mixture before combustion, produced nano-particle aggregates ranging between 8 and 52 nm. For retarded fuel injection strategies, most aggregates had fractal-like morphology similar to diesel soot. Mathis et al. [31] studied exhaust soot particles from GDI engines and identified primary particles with a size of about 27 nm. Choi et al. [32] analysed exhaust soot from a GDI engine, showing chain-like structures ranging from 70 to 400 nm in size, with particle cores between 30 and 80 nm. Uy et al. [33] have recently characterised the nanostructure of gasoline soot. They determined and compared the degree of order of the graphitic planes of soot primary particles extracted from the exhaust gas and from engine oil. Soot-in-oil from GDI engine has not been investigated widely; to the authors׳ best knowledge, its agglomerate size distribution and shape have not been reported in the literature. A summary of the typical dimensions of soot particles from internal combustion engines is reported in Table 1.
Table 1. Typical soot particles dimension from internal combustion engines.

ReferenceEngine typeSoot typeAgglomerate size (nm)Primary particle size (nm)Bonatesta et al. [35]GDIExhaust10–300–Uy et al. [33]GDIOil–8–43Clague et al. [7]CIOil150–>50030–50La Rocca et al. [20]CIOil50–13010–30Table options


The present study is an experimental investigation of soot-in-oil drawn from the oil sump of a modern wall-guided GDI engine. A thorough sample preparation had to be developed to allow for HRTEM imaging of soot-in-oil agglomerates; this is outlined here. Agglomerate and primary particle size distributions are investigated in terms of size, shape and nanostructure. EDX in the TEM allows the elemental components of individual nanoparticles to be investigated. As this technique requires the beam to impinge on the sample for a greater length of time, this technique also benefits from the sample cleaning process developed for HRTEM.
2. Experimental setup and sample preparation

2.1. Experimental equipment

Engine testing was carried out using a 1.6 l, turbo-charged and intercooled, Euro IV, Direct Injection Spark Ignition, gasoline engine with no modifications, available at Oxford Brookes University. The engine technical specifications are given in Table 2.
Table 2. Test engine technical specifications.

Displacement (cc)1598Stroke (mm)77Compression ratio10.5:1Connecting rod length (mm)138.4Combustion chamber4-Valve, central spark plug, pent-roof designEngine typeIn-line 4-cylinderCycle4-stroke spark ignitionFuel injection systemDirect injection common railFuel injectorsSide-mounted, wall-guided sprayMaximum injection pressure (bar)120Maximum engine speed (rev/min)6000Maximum rated torque (Nm)240Table options


The engine was installed on a laboratory test bed and controlled by a Schenck W150 eddy current dynamometer via a CP Engineering CADET engine control and data acquisition system. Fuel consumption was measured via a CP Engineering FMS-400 gravimetric system. The engine was operated for a 30 h time interval at specific steady-state, fully-warm operating conditions crossing a large portion of the part-load running envelope. The delivery of fuel is via a common-rail direct injection system; injection pressure is regulated via the ECU as a function of load and speed, with a maximum value of 120 bar. The fuel used for testing was pump-grade, unleaded gasoline with the following average specifications:
RON=95
MON=85
Stoichiometric AFR=14.4
Nominal latent heat of vaporisation=0.34 MJ/kg
Max sulphur content=50 ppm
Max aromatics content=35% (by volume)
Max renewable content=4.5% (by volume)
2.2. Soot-in-oil sampling

At the beginning of the testing period the engine was flushed twice with clean oil; a further final oil change followed. Each flushing included a full oil and filter change, as well as running the engine for 3 h in fully warm and steady state operating condition at a speed of 1600 rev/min and at a brake load of 15 Nm. The double flush-and-drain procedure was sufficient to obtain drained oil visibly not dissimilar to new oil. Similarly, Arcoumanis et al. [34] employed two equal consecutive flushing procedures to remove most used oil and residue from the engine. The characteristics of soot nanoparticles in engine oil were studied by sampling the lubricating oil at the end of 30 h of operation. Although the mix of operating conditions covered was defined for other purposes, this was sufficiently varied to suggest the range of agglomerates formed would be representative of urban environment use. At the end of the testing, oil samples were drawn from the sump for the investigation of the soot content.
2.3. Soot-in-oil measurements

Soot-in-oil characterisation was performed at the Soot Diagnostics Suite at the University of Nottingham. As suggested by La Rocca et al. [20], samples of soot extracted from engine oil were prepared using a solvent extraction process, diluting the oil at a dilution ratio of 1:60 in heptane. This produces a heptane solution containing a much lower oil content, and also at a suitable low viscosity to allow deposition onto TEM grids. Following deposition, the solvent evaporates rapidly to leave soot particles of varying sizes and aggregations. This process puts little strain on the soot aggregates and it is expected to reveal a structure typical of the soot as it was in the engine oil. Samples were then subjected to close-to-vacuum conditions in order to enhance the evaporation of the solvent. Level of contamination was still considerably high, and its progressive build-up on the sample under the electron beam led to sample becoming gradually darker forming distinctive dark rings as depicted in Fig. 1, which prevented imaging and rendered the samples unsuitable for further analysis.

Fig. 1. TEM image showing effects of contamination and the characteristic dark rings formed at the edge of the area exposed to the electron beam.

Figure options


Two stages of diethyl bathing were employed to reduce contamination and allow for agglomerate size measurements. For HRTEM analysis, centrifugation was performed on the diluted oil/heptane solution following the work of La Rocca et al. [20]. The number of centrifugation stages at 14,000 rev/min and 25 °C for 90 min was increased to six in the present study. After each stage, the liquid phase was replaced with equal amount of pure heptane. Samples were also subjected to 30 min of ultrasonic bathing. 3 μl of the soot suspension in heptane were dispersed onto TEM support films and subsequently washed with diethyl ether.
3. Results and discussion

Fig. 2 shows typical TEM images of agglomerates after solvent extraction. Several 1–2 nm particles were found on the grid. Similar particles were found in diesel soot-in-oil samples in [20] and were considered to be oil additives.
Fig. 2. Agglomerates images (TEM) from soot-in-oil samples prepared by solvent extraction.

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In this work, soot-in-oil particles were measured in terms of their skeleton length, Lsk, and width, Wsk, and fractal dimension. Lsk and Wsk were inferred from 2-D TEM images using an open architecture image processing software, ImageJ, whilst a MATLAB algorithm was created specifically for calculating the fractal dimension. The algorithm followed the iterative method proposed in [21], which is not discussed in details here for brevity. Soot agglomerates were measured based on the skeleton criterium, as this results in a better representation of the aspect ratio [20]. Fig. 3(a) and (b) illustrates the skeleton length and width frequency distribution of the agglomerates. The mean skeleton length, LSk and width, WSk were found to be 153 nm and 59 nm, respectively. 66% of the agglomerates presented a skeleton length between 90 nm and 180 nm, with LSk ranging from 53 nm to 405 nm. Long agglomerates with skeleton lengths longer than 300 nm accounted for 9% of the agglomerates. The skeleton width spanned from 33 nm to 102 nm, with 70% of agglomerates in the range 60–80 nm.
Fig. 3. Frequency distribution of soot-in-oil samples prepared by solvent extraction: (a) agglomerate skeleton length, (b) skeleton width, (c) aspect ratio and (d) fractal dimension.

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GDI soot agglomerate size was found to be comparable to diesel engine soot-in-oil as reported in literature. Soot-in-oil agglomerates drawn from diesel engines show a modest branched morphology, and exist in clusters and chain-like structures with average hydraulic diameter of 100 nm [16]. Similar agglomerates were found by Clague et al. [7] in a study in which soot was compared to black carbon. Diesel soot investigated by La Rocca et al. [20] had an average skeleton length of 131.8 nm measured from TEM projections and were composed of spherical primary particles of 12–40 nm.
In this work, particles with an aspect ratio LSk/WSk<2.5 are considered to be clusters and particles with an LSk/WSk ratio >2.5 to be chains. The present investigation of GDI soot nanoparticles found 53.6% of the agglomerates analysed as clusters with very modest branching, whilst 46.4% were chain-like structures. Typical agglomerates found in such samples are shown in Fig. 2. A similar measurement was carried out in [20], where a slight majority agglomerates was present as chain-like structures; in that investigation, 46% of the agglomerates showed an aspect ratio <2.5 and 54% showed an aspect ratio >2.5.
Fig. 3(d) shows the fractal dimension frequency distribution of the soot agglomerates analysed in the present study. As shown, 97% of the measured Df varied in the range 1.1–1.8; similar fractal dimensions, comprised between 1.2 and 1.74, have been reported by Li et al. [11] in a study on in-cylinder diesel soot. The measured fractal dimension indicates the presence of a majority of short-branched structures. The soot agglomerates analysed in this investigation were not dissimilar to typical agglomerates from diesel engines used oils. Differences in agglomerate sizes could be associated with differences in engine operating conditions, fuel type and details of engine features such as fuel injector. Observations on how engine conditions affect agglomerate size can be found in a sister publication by the authors [35]. In that study, experimental measurements of agglomerate soot size distribution have been taken from the same engine, covering a large portion of the part-load running envelope at different engine speed and load.
HRTEM samples were prepared for analysis as discussed in the methodology section; primary particles size distribution and their internal structure were of interest. Fig. 4 shows the diameter frequency distribution of oil soot primary particles. Soot-in-oil primary particles presented a mean diameter of 36.2 nm with a mode of 32 nm and standard deviation of 12.7 nm. Primary particles diameters spanned from 20 nm to 90 nm, with 88.7% of the particles in the range 20–50 nm, 11.3% equal or larger than 60 nm.
Fig. 4. GDI soot primary particles diameter distribution of soot-in-oil samples.

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Diesel soot-in-oil primary particles have been reported to be in the range 10 nm to 35 nm, with a mean diameter of 20.2 nm [20]. In a separate investigation, Su et al. [36] analysed the microstructure of diesel soot-in-oil primary particles from a Euro IV engine, and found that the primary particle diameter is significantly smaller compared to a conventional diesel engine, specifically in the range 3–15 nm. This was attributed to the higher oxidation rates and their operation at higher pressures and temperature. Primary particles analysed in the present work are found to be larger in sizes compared to size distributions from DI diesel engines [17]. As reported by Bonatesta et al. [35], and in line with the relevant literature [31], [37] and [38], the vast majority of exhaust soot emitted by the wall-guided GDI test engine can be considered as primary particles in the 10 to 100 nm diameter range, whereas in excess of 55% is emitted in nucleation mode (below 50 nm).
Analysis of soot-in-oil samples allows characterisation of the nanostructure of the primary particles as it was at the time it transferred into the lubricating oil from the combustion chamber. In the soot-in-oil primary particles pictured in Fig. 5 and Fig. 6, a core–shell structure similar to that found in diesel particles can be observed. Interestingly, the vast majority of primary particles analysed in this work presented a core-shell structure, along with an unusual amorphous layer covering the particle. This was not observed in other studies of diesel soot particulate reported in the literature. Minimising beam exposure prior to imaging did not result in any significant apparent change in the thickness of this layer, although long beam exposure times have been observed to produce a variable amount of additional amorphous carbon.
Fig. 5. GDI soot-in-oil TEM image showing internal structure of primary particles (Image on the left has contrast enhanced using ImageJ to improve the fringes visibility).

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Fig. 6. Core–shell structure of GDI soot-in-oil primary particles showing central core 25 nm in diameter, shell 16 nm thick and amorphous layer 5 nm thick. A and B show details with contrast enhanced using ImageJ to improve the fringes visibility.

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Primary particle nanostructure details are given in Fig. 6A and B; both detailed images were adjusted in terms of brightness and contrast in order to improve the visualisation of the structure. Soot primary particles show a turbostratic structure, similar to diesel soot samples [20], with characteristic core and shell. Two layers are clearly distinguishable in the shell. The inner layer is of typical graphitic nature. The inner core is 25 nm in diameter while the outer shell measured 16–20 nm in thickness; this was composed of lamellae ordered in an onion-like structure around the inner core, similar to the structures reported in [20] and [24], and covered by a layer of amorphous carbon. The outer shell is significantly thicker than the one observed in Fig. 5, which shows a bucky-onion structure of 8–12 nm. The latter being typical of diesel particles as reported in [20].
Soot reactivity is essentially dictated by the outer shell structure. Although the classic core-shell structure is clearly visible in all particles, the wider graphitic layers concentrically orientated, and typically with fewer reactive sites [39], are covered by an amorphous 5 nm layer with very short segments. This leads to an increase of edge sites and consequently to an increase of overall reactivity as reported by Vander Wal [40]. Uy et al. [33] also reported gasoline soot primary particles being of amorphous structure.
Another interesting feature of the GDI soot particles is the recurrent presence of crystalline structures on the primary particle surface, as depicted in Fig. 7. Prolonged exposure to the electron beam at normal imaging intensities frequently led to decomposition, suggesting many of these are volatile structures. This was also observed by Uy et al. [33]. In Fig. 7a, the spacing between the layers of the particle is about 1 Ĺ, strongly suggesting graphitic nature. Kubicki [41] points out that lamellar graphitic structures are possible and can be formed from the gas phase. This may be more applicable to gasoline derived soot where the hydrocarbons involved are more volatile compared to diesel [36]. Fig. 7b shows a darker particle on the bottom right of the carbon material; being significantly darker despite being much smaller indicates it is a heavier material than the mostly carbon soot particle.
Fig. 7. HRTEM images revealing crystalline structures deposited on soot-in-oil particles.

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Non carbon structures were separately identified using High Angle Annular Dark Field – Scanning TEM (HAADF-STEM); the EDX spectra were obtained from a range of these structures found on the grid. Table 3 shows a selection of the spectra, illustrating the elements most frequently found.

Table 3. EDX spectra from four non-carbon structures found on the grid. The C and O percentages include the contribution from the support film.

ElementParticle 1 (wt%)Particle 2 (wt%)Particle 3 (wt%)Particle 4 (wt%)Al0019.030C71.5853.5242.3750.61Ca2.553.391.740Fe00013.56K04.1600Mg1.671.711.741.33Mo4.05000Na03.700O14.6226.827.2634.5P04.2100S0.712.511.320Si4.7902.080Ti004.440Table options


More generally, TEM-EDX analysis of non-soot nanoparticles in the sample showed the widespread presence of O, consistent with most of these materials being heavily oxidised. P, S, Ca, Zn, Mg, Mo and Na have previously been listed as coming from engine oil additives [33]. All these elements have been observed in this analysis, with S, Ca and Mg observed widely. Similarly, Fe, Cr, Al and Cu were identified as coming from wear metals. Particles with Al and Fe content were identified in this work, Cu could not be identified using EDX-TEM due to the use of Cu TEM grids.
4. Conclusions

Soot agglomerates extracted from engine oil from a modern gasoline direct injection engine have been characterised for the first time, with the aim of assessing size, distribution and shape. The nanostructure of the primary particles was also investigated. A robust methodology to produce samples for TEM and HRTEM was developed and outlined.
Agglomerate size was given in terms of skeleton length, width and fractal dimension. At the macro scale, the GDI soot agglomerates are remarkably similar to agglomerates from light duty diesel engines as reported in the literature. The mean length and width were found to be 153 nm and 59 nm. 54% of the agglomerates presented an aspect ratio <2.5, indicating a small predominance of compact structures with very modest branching. The mean fractal dimension of the agglomerates was calculated to be 1.44.
Conversely, the primary particles differ in nanostructure from a typical diesel soot particle. GDI primary particles are spherical in shape, with some irregularities. The mean diameter was found to be 36 nm. An inner core and outer shell structure was found in the majority of the particles. The wider graphitic layers concentrically orientated, and typically with fewer reactive sites, were covered by an amorphous 5 nm layer with very short segments.
Volatile lamellar graphitic structures were found deposited on the external surface of soot-in-oil primary particles. TEM-EDX analysis of non-soot nanoparticles in the sample showed the widespread presence oil additive elements and wear metals.

 

Interesting info, but did you get permission to post this article? I'm not trying to give you a hard time, just wondering if posting what looks like the entire article or at least a major portion is OK with respect to copyright.

 

Yes, enjoy.

 

The problem could be solved from an angle other than the oil. Design a better chain, one that will resist stretching.

 

They already make the best chain they can. And you would still have the bearings and cams that follow next.

Maybe if they made one that was easy to shorten. Could be done through the oil fill port.

 

This article was published in November of 2013. Now it is May 2016 some 30 months later. Where do we stand now? What is the situation today and what should we do to protect our engines and our pocket books?

 

Interesting but.... and no mention of serious carbon deposits on the intake valves of DI engines that can reduce power by over 20% (from a dyno test on an Audi RS4)..
Do you ***-u-me that Jaguar are using the best possible chains, maybe they are, or they could possibly upgrade the materials used, You only have to to look at modern motorbike chains to see how good they can be..
I don't think stretching is really a good word to describe the problem, yes the chain does get longer, but it is due to wear between the pins and rollers, nothing actually stretches. Good m'bike chains use O rings to seal a high performance grease into that space, another alternative?
Maybe timing belts will be coming back, not in the oil and easier to change than chains.
I have used "by pass" filters on large industrial hydraulic equipment and understand that some big hiway trucks use them and can go over 100,000miles between oil changes, they really work and will keep the soot/carbon out of the oil.
Kleenoil Bypass Oil Filter System - Bypass Oil Filtration - Home
Just need to find a space for one...
Oh, and you really cannot shorten a stretched chain, the pitch has changed and it is done, it might work on a pedal bike, but not for a long cam chain.
So the 4.0 V8s had t chain issues and now maybe the 5.0s, maybe the 4.2 will become more desireable.
Meanwhile, don't think too many, or maybe any, 5.0 XKs will be needing new chains..
Happy motoring

 

They haven't found a solution yet. in all fairness they had set the target date for 2017. make sure you use the specified oil, and keep the oil clean.
Yes the solution will ultimately come down to some method of cleaning the oil or very short oil changes. Clearly the combination of what we are doing has not worked. The good news is that there will be solution since it affects all direct injection cars.

 

Why it is that I was unable to find anything about ILSAC? What is their credentials in this? Who funds them, not just who are some of the participants? Do they have skin in this game?

What they also didn't do was run two alike, or many as they should have, engines side by side to make actual proper test that might then allow anyone to draw a reasonable conclusion that this is not purely stress thus as you claim more frequent oil changes (as would in any way be a benefit. What they have provided is a conclusion based upon a single engine which is anything but a good case study. Lots of cute pictures, lots of words with many syllables, lots of scientific terms but terrible case study. I'm not saying that their test result is not accurate what I am saying is that this test is completely worthless as there is no comparison. They do talk about higher than normal particles in the oil and elude to it but they did did not make the claim that it is causal of the stretched chain nor did they state that the oil was beyond its ability to to perform properly as they cannot based upon a single case study... beyond lame

As the car mfg's continue the trend of going to smaller, usually turbo'd, engines that are seriously stressed in order to provide maximum torque/hp running at higher RPM's to provide higher mpg of course the engine is pushed to it's max therefore will incur a higher degree of failures. DI engine running a high pressure fuel pump will increase stress on the timing belt to what degree I don't know but I'd expect the massive teams of scientists/technicians to take that into account as that is exactly what they are paid to do using extremely accurate software programs which predict such things.

Just because that story is long winded doesn't make it correct and certainly doesn't bridge the chasm that you, Q&C, are trying to claim here. Again, maybe you and this test are correct but this is hardly conclusive proof, it is a poorly done study on a single engine and as I mentioned initially done by an organization for which I have not been able to find any actual background on which makes it that much more questionable/skeptical. One anecdotal engine does not prove anything. Please show me where it states changing the oil WILL stop the chain from stretching, I must have missed that

These guys have more scientific, longer words with many more testimonials - https://www.slick50store.com/faqs
The Ford Escort was the best selling car in the world therefore it must be a great car... same type of logic. Until they do even a semi-decent study there findings all but worthless. I've read where cab companies NEVER changed their oil just their filter with basically toilet - http://wardsauto.com/news-analysis/n...s-oil-fit-life

Because its on the internet and they make claims doesn't make it accurate...

 

It was difficult to read past your first line and I did not. (because the foundation was missing)

ILSAC is the governing body that tells all oil manufactures what the minimum guidelines should be. In this case: the guideline they are setting for 2017 is that all oil manufacturers must state wear on timing chain.

Suspicion based on lack of knowledge disqualifies and argument for me. Its no different than someone who has no formal education arguing against Darwinism. Maybe your inability to find ILSAC reflects more on your will than their credibility?

Incidentally API has found the same regarding carbon wearing timing chains.

 

Very sad that unfounded suspicion is the only thing you bring to the discussion, and so much time has to be lost to just defending credibility, which speaks volumes of your own. Look closely at the bottle of oil for Jaguar 5.0 engine- it states ILSAC g5 certification! thats who ILSAC is.
Their new G6 certification is greatly improved.

 

You would be gullible enough to believe that an internal combustion engine consumes no oil in its lifetime.

Lets just say we should consider ourselves fortunate that you dont run a fish and chips shop.

 

Wow you look like Keaneu Reeves trying to dodge facts, questions, and reality here but you did the same thing in the other two threads. I didn't ask if ILSAC existed, nor why they didn't appear on an oil bottle but had you read a bit further you would have seen that and it certainly would not have fit into your assumptions and... you remind me of an ex who I constantly said she didn't want to bothered with facts and truth as she already made up her mind. Strange how you constantly try to deflect direct questions, why is that?

either your reading comprehension is off by choice or by nature... you completely missed that point once again. The fact that something is on the internet (my example of Slick50 and the never change oil example), without a proper study to support its claims, it is all but worthless and often times actually harmful. Your posting lacked any common study group practice which would mean multiple samples under specifically controlled conditions. Very commonly accepted practice that they did not do therefore it pretty much negates their findings but that doesn't fit into your beliefs I know so let's just ignore that right?

Once again it seems that you've conveniently chosen to take an anecdotal internet posting and use that fuzzy conclusion as an "absolute" in an attempt to bolster your claim that more frequent oil changes WILL prevent damage but thus far nothing in that posting supported that claim even if what they derived from their one-engine test was correct. Could you maybe give us something from a trusted resource that we can verify? Who is ILSAC? Strange but there is next to nothing about them. Love to know who funds them as that would make a huge difference in their credibility.

Constantly throwing irrelevant examples ("your BMW tuner friend said", the ****** in his minivan to support your claim) and unsupported multiple claims doesn't make it more true, it makes you look very desperate. Since you seem to love the Germans so much perhaps you'll remember this little saying by Joseph Geoebbels "“If you tell a lie big enough and keep repeating it, people will eventually come to believe it." Now I'm not saying that what you said is not possibly correct I am saying that your support definitely is lacking hugely and you just keep it coming but none of it directly supports your stance, not even a little bit. Of course, you'll likely come back and say "prove me wrong"... that's not how science works, because I cannot prove aliens DON'T exist doesn't prove they do... same holds true here. You keep making claims but lack scientific studies to prove them. Show me/us where they say that the oil caused the chain to stretch or that changing the oil more frequently will resolve this issue... go ahead but please make it from a reliable source for once just once. That study was worthless in its conclusion let alone supposedly performed by a group I know nothing about and couldn't find out anything on.

I know you and Lother had troubles with your engines, I know oil changes are cheap, none of that supports your claims either. Stick to the points, try to focus and deal with the direct questions rather than going off on a tangent or make personal jabs and support your continuous claim go ahead. You made the initial post, support it/defend it

BTW - I do love fish and chips and am a stanch supporter of fresh oil in fryers

 

[QUOTE=Leeper;1459709]Why it is that I was unable to find anything about ILSAC?



I didn't have any trouble finding a lot of material about the ILSAC by doing a quick Google. Maybe not the answers to all your questions, but certainly enough to give them credibility.


Why are you attacking Q & C for sharing an article that has information which may be of great value to the readers here?Just because you don't like the test protocols? Do you have better information on the issue?If not, spare us the long winded critique that has no meaning facts to add to the issue.

 

The paper's authors look to have been research students at the time so they would not have funding to do any kind of serious multi-engine study or with/without (whatever: oil/type of oil/etc) comparative study.

Right?

I expect engine makers have a lot more info (but may not release it) and ILSAC or whoever would not be relying just on the paper posted. Well, I hope not!

 

This issue, is exactly why Jaguar has been working with Castrol to come up with a lubrication solution. It's why more frequent oil changes are recommended, and why the exclusive recommendation from Jaguar is to use FST additives to help reduce friction. It's why I said before, that TBN numbers are critical to dealing with issues such as soot and acids. I do know that if it were mine, it would be even more compelling to use the same MOA additive I have used for decades. Standard lubricants that are massed produced for consumer use simply doesn't have all it needs to meet the demands of today's engine requirements.

 

I gather I may have missed some information - Is Jaguar currently recommending MORE frequent oil/filter changes than stipulated in the manual that comes with the car? I'm specifically asking about my 2010 XK 5L engine. I do my own oil changes.

I haven't seen such a recommendation....

Thanks!