With the increasing number of gasoline vehicles using direct injection technology today, the issue of Low-Speed Pre-Ignition (LSPI) has gradually caught people's attention. It's a problem unique to gasoline direct injection engines, an unexpected self-ignition of gasoline that occurs before the spark plug fires. If this happens consecutively, it can likely lead to engine failure.
Modern four-stroke gasoline engines operate with the four cycles of "intake, compression, power, and exhaust." During the intake cycle, the high-pressure injector of the direct injection system sprays atomized gasoline diagonally onto the opposing cylinder wall. This atomized gasoline should wait patiently to be ignited by the spark plug. However, contrary to expectations, some of the gasoline combines with the engine oil film on the cylinder wall, liquefying into a gasoline-oil mixture. In the subsequent compression cycle, this mixture is scraped into droplets by the upward-moving piston. As the piston gets closer to the top dead center, conditions in the combustion chamber gradually become conducive for the self-ignition of the gasoline-oil mixture. Eventually, the gasoline-oil mixture self-ignites and explodes before the spark plug ignites it, leading to "Low-Speed Pre-Ignition."
After LSPI occurs, the remaining fuel-air mixture is then ignited by the spark plug in the normal sequence. This subsequent ignition, following the initial explosion, subjects the piston to greater pressure, leading the engine to exhibit a "knocking" sound, a metallic pinging noise. Over time, the overstressed piston may develop cracks, potentially even breaking, causing significant engine damage.
To address LSPI, many lubricant manufacturers have developed new engine oil formulas. These formulas can prevent the atomized gasoline and engine oil from reacting and igniting, thus inherently avoiding the occurrence of LSPI. If your vehicle's engine uses direct injection technology and you frequently experience engine knocking during daily driving, you might consider selecting engine oil products specifically formulated to address LSPI.
