Calcium?

[weather man]

I have noticed on another forum that the ecoboost guys are really fixated on calcium level in the oil. What is up with that?

 

[cbass]

A lot of talk being that calcium in the oil can be a contributor to LSPI, which is what kills DI engines.

I also think that the intake valve being open too early in the exhaust stroke isn't helping anything. Nothing like dumb overlap causing waste to go into the port.

 

[weather man]

Hmmmmm...interesting

Low Speed PreIgnition (LSPI)

Credit to -X- over on Veloster Turbo Forum

Latest LSPI Research Articles (SAE)

2015-03-30 - Mitigating Intensities of Super Knocks Encountered in Highly Boosted Gasoline Direct Injection Engines
Turbocharged gasoline direct injection (TGDI) engines can achieve a very high level of brake mean effective pressure and thus the engines can be downsized. The biggest challenge in developing highly-boosted TGDI engines may be how to mitigate the pre-ignition (PI) triggered severe engine knocks at high loads and low engine speeds. Since magnitudes of cylinder pressure fluctuations during aforementioned engine knocks reach those for peak firing pressures in normal combustion, they are characterized as super knocks.

It is widely believed that the root cause for super knocks is the oil particles entering the engine cylinder, which pre-ignite the cylinder mixture in late of the compression stroke. It is neither possible nor practical to completely eliminate the oil particles from the engine cylinder; a reasonable approach to mitigate super knocks is to weaken the conditions favoring super knocks. This paper reports the results of an experimental investigation on the conditions that potentially lead to PI and methods to suppress super knocks. Various parameters that could affect engine combustion were studied.

It was found that intensities of super knocks varied considerably with the air-fuel ratio for the mixture, the engine cooling temperature, and volatility of the crankcase oil. It was demonstrated that through an appropriate control of the engine operation parameters, the TGDI engine can be operated super-knock free.


2015-04-14 - Investigation of Low-Speed Pre-Ignition in Boosted Spark Ignition Engine
This paper presents the results of study low-speed Pre-ignition (LSPI) on highly supercharged spark ignition engines. It was investigated on both a gasoline direct injection (GDI) engine with turbo and a port fuel injection (PFI) engine with turbo to find the individual characteristics of LSPI. In terms of the PFI engine, influence of different parameters control strategy such as air-fuel ratio and injection timing on pre-ignition was investigated. In terms of the GDI engine, influence of different control strategies such as injection quantity, first and second injection timing, the second injection ratio, coolant temperature, exhaust valve closing (EVC) and intake manifold temperature (MAT) were investigated. In addition, CFD analysis was extensively used to understand test results including wall film, air-fuel ratio distribution and temperature distribution at top dead centre (TDC). For GDI engine in this paper, pre-ignition (PI) results from the combine action of wall film, temperature distribution at TDC and air- fuel ratio distribution at TDC. Enrich air-fuel rate have effective suppression of low-speed Pre-ignition on the GDI engine and the PFI engine.


2015-04-14 - Experimental Study on Pre-Ignition and Super-Knock in Gasoline Engine Combustion with Carbon Particle at Elevated Temperatures and Pressures
Occurrence of sporadic super-knock is the main obstacle to the development of advanced gasoline engines. One of the possible inducements of super-knock, agglomerated soot particle induced pre-ignition, was studied for high boosted gasoline direct injection (GDI) engines. The correlation between soot emissions and super-knock frequency was investigated in a four-cylinder gasoline direct injection production engine. The test results indicate that higher in-cylinder soot emission correlate with more pre-ignition and super-knock cycles in a GDI production engine. To study the soot/carbon particles trigger super-knock, a single-cylinder research engine for super-knock study was developed. The carbon particles with different temperatures and sizes were introduced into the combustion chamber to trigger pre-ignition and super-knock. Consistent with the testing conditions in the GDI production engine experiments, under similar pressure and temperature near the firing TDC, the test results in the single-cylinder research engine indicate that carbon particles with higher temperature and larger diameter could directly lead to pre-ignition and super-knock. Small carbon particles like soot emission could not lead to pre-ignition and super-knock.


2015-04-14 - Experimental Studies on the Occurrence of Low-Speed Pre-Ignition in Turbocharged GDI Engines
In the present paper the results of a set of experimental investigations on LSPI are discussed. The ignition system of a test engine was modified to enable random spark advance in one of the four cylinders. LSPI sequences were successfully triggered and exhibited similar characteristics compared to regularly occurring pre-ignition. Optical investigations applying a high speed camera system enabling a visualization of the combustion process were performed. In a second engine the influence of the physical properties of the considered lubricant on the LSPI frequency was analyzed. In addition different piston ring assemblies have been tested. Moreover an online acquisition of the unburned hydrocarbon emissions in the exhaust gas was performed.

The combination of these experimental techniques in the present study provided further insights on the development of LSPI sequences. In particular strong evidence enabling the identification of the fundamental trigger of premature, local auto-ignitions has been found. The results of the optical investigations reveal that pre-ignition is initiated in the immediate vicinity of glowing solid particles. The particles either result from the flaking of deposits or as a consequence of the contamination of the combustion chamber subsequent to a pre-ignition event.


2015-04-14 - An Experimental Investigation on Low Speed Pre-ignition in a Highly Boosted Gasoline Direct Injection Engine
When highly boosted, turbocharged gasoline direct injection (GTDI) engines can achieve very high torque at low engine speeds and thus the engines can be downsized considerably. One of the challenges that have been faced in developing GTDI engines is the pre-ignition occurring when the engines are operated in the low-speed/high torque zone, known as low-speed pre-ignition (LSPI). LSPI triggers severe engine knocks with intensities much greater than those of spark knocks and thus characterized as super or mega knock. The root cause for LSPI is not yet clear; however, many investigators believe that the lubrication oil entering the engine cylinder is highly responsible for LSPI.

This study reports the results of an experimental investigation on LSPI in a highly boosted GTDI engine. Various parameters that could affect engine combustion were studied, including fuel injection strategy, valve timing, fuel dilution of the engine crankcase oil, oil and coolant temperatures, equivalence ratio for the air-fuel mixture, etc. It was found in this study that LSPI could occur as an isolated event, a couple of events in sequence, or a trail of events. Although occurring randomly in timing, LSPI is a repeatable phenomenon for abnormal combustion in the low-speed/high torque zone.

Frequencies and patterns for LSPI could be influenced considerably by certain engine operation parameters. Intensities of super knocks triggered by LSPI varied considerably with the crank angles for pre-ignition, and some LSPI event even could trigger super knock. It was noticed in this study that the oil loading in the blowby recirculation had a stronger link to the LSPI than oil from other paths entering the cylinder. Through an appropriate control of the engine operation parameters, the GTDI engine can be operated super-knock free although pre-ignitions may not be eliminated completely.


2015-04-14 - Numerical Simulation to Understand the Cause and Sequence of LSPI Phenomena and Suggestion of CaO Mechanism in Highly Boosted SI Combustion in Low Speed Range

2D and 3D numerical simulations were conducted in order to understand and quantitatively clarify the possibility of several causes such as deposit, oil droplet and some particle. The possibility that CaCO3 additive to lubricant oil behaves to change into CaO in combustion process and exothermic reaction is occurred with adsorption of CO2 in following process was suggested as a main cause of LSPI. Finally we understand that CaO particle, oil droplet and deposit seem to be the main causes of 1st LSPI and deposit and CaO particle seem to be the main causes of 2nd and later LSPI cycles.


2015-04-14 - Investigation and Improvement of LSPI Phenomena and Study of Combustion Strategy in Highly Boosted SI Combustion in Low Speed Range
LSPI is an important issue to 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 extracted the major items which affect the possibility of LSPI. Coolant temperature and Ca additive to lubricant had strong effect on the frequency of LSPI. Combustion strategy of strong miller cycle and LPEGR are also studied and compared in very high BMEP condition.


2015-04-14 - Visualization and Analysis of LSPI mechanism Caused by Oil Droplet, Particle and Deposit in Highly Boosted SI Combustion in Low Speed Range
Endoscope and high speed video were attached to an actual engine and oil behavior and combustion were observed. Light induced fluorescence was applied to the observation of oil and combustion was observed by direct light. Many LSPI events were obtained to analyze the causes, sequence and mechanism. Several causes of particle, deposit and oil droplet are recognized and sometimes started at the piston crevice area. Luminous Flame was observed during expansion stroke of LSPI. Red heat particles are observed in several cycles after 1st LSPI which would cause following LSPI cycles.


2015-04-14 - LSPI Performance of Commercially Available Lubricants Low Speed Pre-Ignition (LSPI) is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged engines. Numerous researchers have previously reported that the frequency of LSPI is sensitive to engine oil composition in controlled laboratory and engine-based studies. Very limited data has been published regarding the performance for commercial formulations and performance of North American and European formulations in particular is unknown.

Despite the lack of information on how commercially available lubricants affect LSPI in turbocharged gasoline engines, the industry is actively developing tests to facilitate the development of engine oil specifications to suppress LSPI. In this study, LSPI performance results from a range of commercially available engine oils from the North American market are presented. LSPI performance was assessed using a GM 2.0L Ecotec engine installed on a conventional engine dynamometer test stand. The test cycle and engine operating conditions employed were consistent with those being considered for industry tests, and therefore results from this study are expected to provide a good indication of how currently available commercial engine oil formulations will perform in likely industry tests. Results showed that commercially available lubricants exhibit a wide range of variability in LSPI performance.

Consistent with results from other recent publications, calcium concentration was found to impact LSPI performance. However, the variation in calcium concentration alone did not explain the variability in the LSPI response between different formulations. Detailed analysis of engine performance and in-cylinder pressure data show that other factors such as engine operating conditions play a significant role, and suggests that a holistic engine oil formulation approach is warranted to ensure requisite LSPI performance.


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[Greg Hazlett]

I have noticed that as well; Amsoil has revised their statement on the Sig series oil (25k or 12 months) to replacing the oil every 15K so makes me wonder if there is something legitimate to it...or is the DI diluting the oil which hurts viscosity? I know from changing the oil and emptying the catch cans in the EBM/F150 there is a very strong fuel smell.

 

[weather man]

I have noticed that as well; Amsoil has revised their statement on the Sig series oil (25k or 12 months) to replacing the oil every 15K so makes me wonder if there is something legitimate to it...or is the DI diluting the oil which hurts viscosity? I know from changing the oil and emptying the catch cans in the EBM/F150 there is a very strong fuel smell.

If I remember right, wasn't there a particular cylinder that usually failed? it would make sense that oil droplets being ingested would have a preferential path in the intake.

It was interesting that oil droplets coming back through the exhaust port could also contribute. If exhaust port timing didn't change between the 15 and 16 model, seems that would not be a big factor with the ecoboost.

 

[cbass]

I remember people pointing to cyl 2 & 3 as the common ones, but there was somebody quick to claim cyl 1.

VW and BMW DI engines recommend walnut blasting after a certain amount of miles. Clears the intake path. I don't know enough about ecoboost engines to know if it would help, but it was to remove carbon buildup in the ports and the back of the valves. Would just cake on and look like a smoker's lung.

With the advent of the higher compression turbo DI engines, I would be trying to find every little thing to reduce chances of catastrophic failure. They might not be "strung out" in the sense of rods snapping or heads lifting, but they are strung out in the sense that little shit seems to be causing giant issues.

 

[weather man]

Interesting after doing some more reading that the auto industry does appear to be concerned about the possible link between calcium and LSPI.

Of course, if the oil is kept out of combustion chamber, it becomes a moot point.

 

[Greg Hazlett]

Interesting after doing some more reading that the auto industry does appear to be concerned about the possible link between calcium and LSPI.

Of course, if the oil is kept out of combustion chamber, it becomes a moot point.

Ding ding ding....