Here is some of the information I am referencing if you interested:
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 (http://papers.sae.org/2015-01-0084/)
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 (http://papers.sae.org/2015-01-0751/)
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 (http://rd.bizrate.com/rd?t=http://w...et-set.html?utm_source=shopzilla&utm_medium=p f%26utm_content%3Ddc%26utm_campaign%3DPartsGeek%2B ShopZilla%26fp%3Dpp%26utm_term%3DNissan%2BIntake%2 BManifold%2BGasket%2BSet&mid=192248&cat_id=22000200&atom=10681&prod_id=&oid=2019191402&pos=1&b_id=18&bid_type=0&bamt=a5fedf14fd8fec0d&cobrand=1&ppr=8b7f88146f61a2f5&af_sid=76&mpid=6835-05037490&brandId=722591&keyword=intake%20manifold&rf=af1&af_assettype_id=10&af_creative_id=2912) 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 (http://papers.sae.org/2015-01-0752/)
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.
